Safety Analysis of Intersections along Fenn Street
Safety Analysis of Intersections along Fenn Street
December 2004 Berkshire Regional Planning Commission 1 Fenn Street, Suite 201 Pittsfield, MA 01201
Funded by Federal Highway Administration, through Massachusetts Highway Department, for the Berkshire Metropolitan Planning Organization
Executive Summary The 2003 Regional Transportation Plan recommends a safety evaluation for intersections along Fenn Street in Pittsfield. Accordingly, the Berkshire Regional Planning Commission performed a safety study in June, 2004. This analysis focused on three main intersections along Fenn Street: First Street, Second Street and Fourth Street (see Locus Map). All three intersections are controlled by traffic signals. The well-accepted intersection safety improvement methods were utilized for the study. First, records of accidents that occurred at these intersections from 1998 to 2001 were analyzed to identify high accident types and patterns. Thereafter, an on-site observation study was conducted. Finally, the countermeasures for safety problems were developed. The Fenn Street/First Street intersection had the highest number of accidents, but the Fenn Street/Fourth Street intersection had the highest accident rate. Right angle accidents were the predominant pattern at these intersections. Between 30-40% of accidents at First Street/Fenn Street and Fourth Street/Fenn Street occurred during nighttime. Therefore, the adequacy of street lighting and nighttime visibility of signs should be checked. The corner sight distance is inadequate for vehicles turning right from the eastbound approach of the Fenn Street/First Street intersection and from the westbound approach of the Fenn Street/Second Street intersection. Therefore, “NO TURN ON RED” signs should be installed on those two approaches. The turning radii were found to be inadequate on many approaches to the intersections. At the First Street/Fenn Street intersection, due to the inadequacy of turning radius, vehicles turning right from the southbound approach to Fenn Street were seen coming to a complete stop before turning. This unexpected and sudden slow-down of turning vehicles gives rise to an increased risk of rear-end collisions. Since right-of-way limitations make increasing curb-radius difficult, the approach speed of First Street should be reduced. At the Fenn Street/Second Street intersection, the designated width for on-street parking on the eastbound approach of Fenn Street is inadequate. Therefore, either the prohibition of on-street parking on this approach or widening of available parking space should be considered. At the same intersection, on-street parking on the right side of the westbound approach reduces the visibility and maneuverability for vehicles entering from a nearby driveway. Therefore, on-street parking should not be allowed beyond that driveway (towards intersection). Instead, there is adequate space to provide on-street parking on the left side on the same approach. At the Fenn Street/Fourth Street intersection, three rear-end accidents have occurred when the pavement was either wet or icy. Therefore, road surface friction and adequacy of crown for drainage on all approaches should be checked. At the same intersection, there have been several angle accidents despite the presence of “NO TURN ON RED” signs on all approaches. The adequacy of yellow period and the tendency for repeated violation of traffic signals should be checked.
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Table of Contents
Executive Summary ............................................................................................................ ii 1.0 Introduction............................................................................................................. 1 2.0 Analysis................................................................................................................... 1 2.1 Accident trends ................................................................................................... 1 2.2 Accident types..................................................................................................... 3 2.3 Accidents by road surface condition................................................................... 3 2.4 Accidents by lighting condition .......................................................................... 4 2.5 Severity of accidents ........................................................................................... 4 2.6 Accident rates...................................................................................................... 4 2.7 Pedestrian and bicycle accidents......................................................................... 6 2.8 Cost of accidents ................................................................................................. 7 2.9 Summary of analysis........................................................................................... 7 3.0 Collision Diagrams ................................................................................................. 8 3.1 Fenn Street/First Street ....................................................................................... 8 3.2 Fenn Street/Second Street ................................................................................... 8 3.3 Fenn Street/Fourth Street .................................................................................... 8 4.0 On-Site Observations .............................................................................................. 9 4.1 Fenn Street/First Street ....................................................................................... 9 4.2 Fenn Street/Second Street ................................................................................. 11 4.3 Fenn Street/Fourth Street .................................................................................. 13 5.0 Condition Diagrams .............................................................................................. 14 6.0 Conclusions........................................................................................................... 15 Appendix 1: Figures.......................................................................................................... 17 Appendix 2: Collision Diagrams ...................................................................................... 22 Appendix 3: Accident Rate Formula ................................................................................ 25 Appendix 4: On-site Observation Sheets.......................................................................... 26 Appendix 5: Condition Diagrams ..................................................................................... 32
iii
1.0
Introduction
The 2003 Regional Transportation Plan (RTP) recommends a safety evaluation for intersections along Fenn Street. Accordingly, the Berkshire Regional Planning Commission (BRPC) performed a safety study in 2004. The results of the study are presented in this report. The findings of this study will form the basis for a future detailed study undertaken by a consultant to design safety improvements and for implementation. 1.1
Study area
This analysis focused on three main intersections along Fenn Street: First Street, Second Street and Fourth Street (see Locus Map). All three intersections are controlled by traffic signals. East Street and North Street intersections, which are located at the east and west ends of Fenn Street, were not considered. Both East Street and North Street are four-lane roads, which were (or will be) subjected to operational and geometric changes (e.g., road widening and alignment of East Street, on-street parking and signal improvements on North Street). Therefore, these two intersections were excluded from the analysis. The minor intersections along the corridor, such as Allen Street and Third Street were not considered as these intersections experience very few accidents. The approximate length of Fenn Street from North Street to East Street is 0.62 miles. 2.0
Analysis
The standard accident data analysis methods were used in this evaluation. While the RTP diagnoses were based on the 1990-97 accident data, this analysis utilized 1998-2001 accident data provided by the Massachusetts Highway Department. Data analysis was performed in several ways to identify safety problems: • Accident trends • Accident types • Road surface condition • Lighting condition • Severity of accidents • Accident rates • Pedestrian and bicycle accidents • Cost of accidents 2.1
Accident trends
Refer to Table 1 and Figure 1 in Appendix 1 for numbers of accidents reported at these intersections from 1998 to 2001. The Fenn Street/First Street intersection reported the highest number of accidents; the Fenn Street/Second Street intersection reported the least number of accidents. However, since 1999, the number of accidents occurred at the Fenn Street/Second Street intersection has remained unchanged (i.e., no reduction).
1
Locus Map
4 0
125 250
Fourt h
>
> Fenn S
East
S tr e e
500 Feet
Stree t
Seco nd St reet
North Stree t
First Stree t
Rail line
> tr e e t
s Ea
t tS
re
et
t
Pittsfield
2
An interesting observation is the very high numbers of accidents at Fenn Street/Fourth Street (in 1998) and at Fenn Street/First Street (in 2000) and sharp decline in accidents in the following year. It appears Fenn Street/ Fourth Street has been able to maintain a relatively low accident rate since the high accident occurrence in 1998. The same cannot be said with certainty about Fenn Street/ First Street due to lack of data for sufficient numbers of “after peak” years. Table 1: Accidents on intersections along Fenn Street Fenn/ First
Year
2.2
Fenn/Second
Fenn/ Fourth
Number
Percentage
Number
Percentage
Number
Percentage
1998
8
27%
1
7%
10
48%
1999
6
20%
4
31%
3
14%
2000
13
43%
4
31%
3
14%
2001
3
10%
4
31%
5
24%
Total
30
100%
13
100%
21
100%
Accident types
As indicated in Table 2 and Figure 2 in Appendix 1, right angle accidents are the predominant pattern at all these intersections. The probable causes for right angle accidents at signalized intersections are restricted sight distance, high approach speed, and inadequate signal timing or type of signals. The general countermeasures include removal of sight obstructions, restriction of parking near corners, installation of warning signs, adjustment of yellow interval, etc. This study will attempt to identify pertinent countermeasures for these intersections. Please refer to collision diagrams presented in Appendix 2 for more information on accident types and related patterns. Table 2: Accidents by type Fenn/ First
Type
2.3
Fenn/Second
Fenn/ Fourth
Number
Percentage
Number
Percentage
Number
Percentage
Angle
19
63%
9
69%
14
67%
Rear end
5
17%
3
23%
3
14%
Other
6
20%
1
8%
4
19%
Accidents by road surface condition
Table 3 and Figure 3 in Appendix 1 indicate that majority of the accidents occurred when the pavement was dry. In general, percentage distribution of road surface conditions at the times of accidents at intersections is similar. Therefore, no particular road surface conditions contributory to high accidents were identified.
3
Table 3: Accidents by road surface Fenn/ First
Surface
2.4
Fenn/Second
Fenn/ Fourth
Number
Percentage
Number
Percentage
Number
Percentage
Dry
21
70%
10
77%
16
76%
Wet
5
17%
2
15%
3
14%
Snowy
1
3%
0
0%
0
0%
Icy
2
7%
1
8%
2
10%
Accidents by lighting condition
Table 4 and Figure 4 in Appendix 1 indicate that most accidents occurred during daytime. However, the nighttime accident rates at First Street/Fenn Street and First Street/Fourth Street intersections are high. The most likely reason for nighttime accidents is poor visibility. The general countermeasures include improving street lighting, installation of reflectorized signs and pavement markings, and removal of distracting commercial lighting and other sources of glare. The field visit will investigate the contributory factors for nighttime accidents. Table 4: Accidents by lighting condition Fenn/ First
Type
2.5
Fenn/Second
Fenn/ Fourth
Number
Percentage
Number
Percentage
Number
Percentage
Daylight
19
63%
9
69%
13
62%
Dark[Road Lit]
10
33%
3
23%
8
38%
Dawn or Dusk
0
0%
1
8%
0
0%
Severity of accidents
Table 5 and Figure 5 in Appendix 1 break down accidents by severity. As seen from Figure 5, there have been no fatal accidents. The ratio of injury accidents to property damage only (PDO) is high. In particular, 60 percent of accidents at First Street/Fenn Street have resulted in injuries. The types of accidents that resulted injuries will be analyzed using collision diagrams (section 3.1). Table 6: Accidents by severity Fenn/ First
2.6
Fenn/Second
Fenn/ Fourth
Fatal
Injury
PDO
Fatal
Injury
PDO
Fatal
Injury
PDO
0
18
12
0
7
6
0
10
11
Accident rates
A commonly used method for identifying high accident intersections is to compare accident rates with average area-wide accident rates. The rate used in this analysis is accidents per million entering vehicles (MEV). The accident rate formula is given below.
4
Accidents per MEV
=
number of accidents in one year X 1 million 24-hour intersection entering volume X 365
Tables 7-9 give accident rates for the intersections along Fenn Street. The estimated values were used when Average Daily Traffic (ADT) data were not available. Table 7: Fenn Street and First Street (signals) Year
ADT Fenn Street
ADT First Street
1998
4,500
18,000
8.21
8
1999
4,500
18,000
8.21
6
2000
4,500
18,000
8.21
13
2001
4,500
18,000
8.21
3
32.84
30
Total
MEV
Accidents
Accident rate is 0.91 per MEV. Table 8: Fenn Street and Second Street (signals) Year
ADT Fenn Street
ADT Second Street
1998
4,500
2,800
2.66
1
1999
4,500
2,800
2.66
4
2000
4,500
2,800
2.66
4
2001
4,500
2,800
2.66
4
10.64
13
Total
MEV
Accidents
Accident rate is 1.22 per MEV. Table 9: Fenn Street and Fourth Street (signals) Year
ADT Fenn Street
ADT Fourth Street
1998
4,500
4,500
3.29
10
1999
4,500
4,500
3.29
3
2000
4,500
4,500
3.29
3
2001
4,500
4,500
3.29
5
13.16
21
Total
MEV
Accidents
Accident rate is 1.60 per MEV. The values given in Table 10 represent average accident rates for signalized and unsignalized intersections for 2002.
5
Table 10: Average accident rates (accidents per MEV) Location
Signalized intersections
Unsignalized intersections
Statewide
0.87
0.66
0.65
0.34
District 1 Source: MassHighway
Table 11 summarizes accident rates, comparative area-wide average accident rates, and critical accident rates for the intersections. The critical accident rate (RC) is used to determine if an intersection is a high accident location or not. If the accident rate at an intersection is greater than the critical accident rate, that intersection is considered as a high accident location. The interpretation of a high accident location can be phrased as “We are 95% confident that the intersection is a high accident location, based on its accidents, traffic volume, and comparative area-wide average accident statistics.” The formulae used for the critical accident rates presented in Table 11 and a sample calculation is given in Appendix 3. Table 11: Comparison of accident rates against average rates for District 1 Average rate for District 1 (per MEV)
RC
Ratio of accident rate/RC
0.91
0.65
1.05
0.87
Fenn Street/ Second Street
1.22
0.65
1.27
0.96
Fenn Street/ Fourth Street
1.60
0.65
1.23
1.30
Location Fenn Street/ First Street
Accident rate (per MEV)
In comparison to average accident rates for MassHighway District 1, the three intersections have above-average accident rates. However, based on the critical accident rate, only Fenn Street/Fourth Street can be treated as a high accident location. Fenn Street/First Street, which has the highest number of accidents, is not identified as a high accident location because of the large volume of traffic that passes through the intersection daily. Based on the findings of the analyses presented in sections 2.1-2.6 (e.g., severity of accidents, lighting condition, accident rate, etc), the three intersections will be analyzed further using field data. 2.7
Pedestrian and bicycle accidents
As indicated in Table 12, pedestrian and bicycle accidents are rare. The availability of push buttons at signalized intersections and paved sidewalks may be contributory for low pedestrian and bicycle accidents. However, this study will investigate possible measures for further improving safety for pedestrians and bicyclists.
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Table 12: Pedestrian and bicycle accidents
2.8
Fenn St/ First St
Fenn St/ Second St
Year
Pedestrian
Bicycle
Pedestrian
Bicycle
Pedestrian
Fenn St/ Fourth St Bicycle
1998
0
0
0
0
0
0
1999
0
0
0
1
1
0
2000
1
0
0
0
0
1
2001
0
0
0
0
0
0
Total
1
0
0
1
1
1
Cost of accidents
The approximate cost of accidents was estimated using the Federal Highway Administration’s (FHWA) cost data. The purpose of calculating accident costs is to emphasize the severity of safety problems and thereby highlight the need for remedial measures. Table 13 presents costs developed by FHWA using 1994 dollar values. Table 13: Cost of accidents by severity (FHWA) Descriptor Fatal Incapacitating
Cost (1994) $2,600,000 $180,000
Injury evident
$36,000
Injury possible
$19,000
Property damage only
$2,000
Since the traffic accident reports do not specify the level of injury, an injury accident was assumed to cost $27,500 (average of injury evident and injury possible values). Based on the accident severity data presented in Table 6, costs of accidents at these intersections were estimated (Table 14). Fenn Street/First Street reported the highest cost due to its high number of injury accidents. Table 14: Cost of accidents 1998-2001 Location
2.9
Cost (1994 dollars)
Fenn Street/ First Street
$519,000
Fenn Street/ Second Street
$204,500
Fenn Street/ Fourth Street
$297,000
Summary of analysis
The main findings of accident data analysis include: • Fenn Street/First Street intersection has the highest number of accidents. • Right angle accidents are the predominant pattern at all intersections.
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• • • • • 3.0
The percentage of nighttime accidents at Fenn Street/First Street and Fourth Street/Fenn Street is very high. Sixty percent of accidents occurred at Fenn Street/First Street intersection have resulted in personal injuries; the injury accident rate at the other two intersections is between 45-55 percent. The accident rates at the three intersections are higher than the area-wide annual accident rates. However, based on critical accident rate methodology, only Fenn Street/Fourth Street is identified as a high accident location. High percentages of severe accidents, nighttime accidents and above-average accident rate warrant further analysis of these intersections using field data. Pedestrian and bicycle accidents are few. Collision Diagrams
Collision diagrams are used to display and identify accident patterns. They provide information such as approximate location, type of accidents, time of day, weather, and pavement conditions that are helpful for identifying probable causes for accidents. Collision diagrams for all four intersections are attached in Appendix 2. Some of the patterns visualized by collision diagrams (type of accidents, severity, etc) were discussed previously. Other notable patterns observed from collision diagrams for each intersection are described in sections 3.1-3.3. 3.1
Fenn Street/First Street
Right-angle accidents, which are the prevalent accidents on this intersection (63 percent), are equally spread at all four intersecting approaches. The majority of right angle accidents resulted in injuries. There have been five rear end accidents, four of them involving vehicles on First Street. Notably, four out of five rear-end accidents resulted in injuries. Probable reasons for rear-end accidents at this intersection are inadequate signal timing and large volume of turning vehicles. There have been three left turn accidents. These left turn accidents can be attributed to permitted left turns at the intersection. 3.2
Fenn Street/Second Street
The majority of right angle accidents have occurred between northbound traffic on Second Street and westbound traffic on Fenn Street. Another revelation from the collision diagram is that all accidents involving southbound traffic resulted in injuries. Two of the three rear-end accidents were involving southbound vehicles. There has been one bicycle accident. 3.3
Fenn Street/Fourth Street
Southbound traffic on Fourth Street involved in majority (57 percent) of the reported accidents. Moreover, the majority of right angle accidents were involving southbound vehicles with eastbound and westbound vehicles. There have been one reported rear-
8
accident on each direction, and three of these four accidents have occurred when the pavement was wet or icy. 4.0
On-Site Observations
To investigate physical characteristics of the intersections and to identify probable causes for accidents, the study team made a site visit on 30th June, 2004. First, the observers drove though each intersection several times from all possible approaches. Thereafter, the driver behavior at the intersections was observed. Next, an “On-Site Observation Report” was completed for each intersection (see Appendix 4). This was followed by physical measurements of intersections and taking digital photographs. The following sections describe the main observations of the field visit. 4.1
Fenn Street/First Street
This intersection is fairly busy during daytime. There are dense roadside developments, except at the southeast corner of the intersection. Therefore, right turns on red periods (RTOR) are not allowed from the westbound approach of Fenn Street. As seen from Photo 1, the sight distance for RTOR from the eastbound approach of Fenn Street is inadequate (view impeded by a building at the northwest corner). Moreover, five accidents have occurred between eastbound and southbound vehicles. Therefore, RTOR for eastbound vehicles should not be allowed.
Photo 1: View looking north from eastbound stop line on Fenn Street
The turning radii for right turning vehicles from the southbound and eastbound approaches seem inadequate. As a result, many turning vehicles either encroach upon the
9
opposing lane (of the receiving approach) or come to a complete stop and make a sharp turn to get onto the correct receiving lane. In the absence of a separate right turn lane, vehicles having to stop and turn during green time greatly reduces the number of vehicles that can pass through the intersection. Moreover, this gives rise to the risk of rear end collisions between turning vehicles and through vehicles. Therefore, the possibility of increasing turning radii should be investigated (without unduly increasing walking distance for pedestrians). If the available right-of-way restricts any geometric improvements, an alternative suggestion is to post an appropriate speed limit on the southbound approach of First Street (presently, there are no speed limit signs). A reduced approach speed limit, which is consistent with the existing speed limits for urban settings, should help to minimize the risk of rear end accidents between turning vehicles and through vehicles. The stop line on the southbound approach of First Street has been shifted about 20 feet away from the pedestrian crossing (Photo 2). This might have been done due to the inadequacy of curb radius for trucks turning right onto First Street to travel north from the westbound approach of Fenn Street. There are two conceivable drawbacks of this layout: reduced storage capacity of left turn lane on the southbound approach, and increased distance that a stopped vehicle on the southbound approach has to travel to clear the intersection during green time. If curb radius is increased to accommodate truck turns, it would result in a longer walking distance for pedestrians crossing at this location. Unless a way to reroute trucks can be found, the above-mentioned drawbacks will prevail at this intersection.
Photo 2: Separation between pedestrian crossing and stop line
10
The road surface of the eastbound approach of Fenn Street lacks proper crown. As a result, during rain, water doesn’t drain away from the road surface. To improve this situation, this approach should be resurfaced. A driveway is located about 50 feet north of the intersection off First Street. This driveway provides access to few parking spaces. However, vehicles entering and exiting from this driveway interfere with the queue storage area of southbound traffic on Fenn Street. Therefore, the possibility of closing this driveway and providing an alternative access to the parking spaces should be considered. 4.2
Fenn Street/Second Street
This is a signalized four-way intersection with a relatively low traffic volume in comparison to the previously discussed intersection. However, RTOR vehicles from the westbound approach appear to have insufficient corner sight distance (Photo 3). Offstreet parking diminishes the visibility of oncoming traffic for RTOR vehicles from the westbound approach. Therefore, right turns during red should be prohibited.
Photo 3: View looking south from westbound approach of Fenn Street
The turning radius for vehicles turning right from Fenn Street eastbound direction is inadequate. As a result, these vehicles encroach upon the opposing traffic lane of the northbound approach. Therefore, the curb radius at the southwest quadrant should be increased to facilitate right turns. On-street parking is allowed on the right side of the eastbound approach of Fenn Street. However, the designated width of the parking lane is only 2 feet (Photo 4). Any vehicle parking in these spaces reduces the effective travelway width for westbound traffic. 11
Therefore, either the prohibition of on-street parking or widening of available parking space should be considered. On-street parking is allowed on the right side of the westbound approach of Fenn Street. However, an access driveway is located within the designated parking area (Photo 5). Therefore, on-street parking should not be allowed beyond this driveway (towards intersection). Any parked vehicle beyond the driveway reduces sight distance and maneuverability of vehicles entering Fenn Street from that driveway. Instead, there is adequate space to provide on-street parking on the other side of the street. Therefore, if necessary, on-street parking can be allowed on that side.
Parking sign
Photo 4: Inadequate on-street parking space on eastbound approach of Fenn Street
12
Driveway Parking
Photo 5: Conflict between parking layout and driveway location on Fenn Street
4.3
Fenn Street/Fourth Street
This is a four-way signalized intersection. It has the highest accident rate among the three intersections. The eastbound approach of Fenn Street has a downgrade about 3-5 % (Photo 6). However, there have been only one reported rear-end accident on that approach. Moreover, the other three approaches have also recorded one rear-end accident during the same period. Most these accidents occurred on wet or icy pavements. Therefore, accidents do not show a correlation with the slope of the eastbound approach. Instead, friction of the road surface of all approaches should be checked. Another suggestion is the proper snow removal during winter.
13
Photo 6: Downgrade on eastbound Fenn Street approaching Fourth Street
In general, corner sight distances are inadequate. However, “NO TURNS ON RED” signs are present on all approaches. There seems to be adequate signage to alert drivers to the lack of corner sight distance, and thereby prevent risky RTOR. In spite of the signage, there have been several angle accidents at the southeast and southwest corners. Therefore, the other possible contributory factors to angle accidents such as inadequate yellow interval and repeated driver violations of traffic signals should be investigated. The street lighting appears somewhat inadequate (based on the number of street lights available). As Table 4 indicates, 38% of accidents have occurred during nighttime. At least five angle accidents have occurred during nighttime. It may be possible that during nighttime, traffic signals turn into flashing yellow/red mode. In the absence of signals, inadequate nighttime visibility may compound the right-of-way sharing difficulties for drivers. Therefore, the possibility of improving street lightings and/or installation of retroreflectorized signs should be explored. On-street parking is allowed on one side of Fenn Street. While parking maneuvers can give rise to conflicts, accident records indicate only one accident that involved a parked vehicle. Therefore, on-street parking does not appear to be a primary reason for accidents. 5.0
Condition Diagrams
Based on the measurements taken of the roadway and immediate surroundings, condition diagrams were prepared for each intersection. Condition diagrams were prepared as scaled drawings and these are helpful for relating accident patterns and probable causes to the physical features on and near the roadway. Appendix 5 presents the condition
14
diagrams and these diagrams can also be used when developing detailed safety improvements.
6.0
Conclusions
The safety of three intersections along Fenn Street (First Street, Second Street and Fourth Street) was evaluated. These are four-way signalized intersections. To identify safety problems and to recommend countermeasures, the study team followed a well-established accident evaluation methodology, which included an analysis of crash data, field visits, and preparation of collision and condition diagrams. The accidents reported between 1998 and 2001 were used in the analysis. The main findings of the study include: • The accident rates at all three intersections are higher than the District 1 area-wide average accident rates. •
Fenn Street/First Street experienced the highest number of accidents during this period. However, due to higher number of accidents in comparison to traffic volume passing the intersection, only Fourth Street/Fenn Street is identified as a high accident location.
•
Right angle accidents are the predominant pattern at these intersections. Moreover, at First Street/Fenn Street and Fourth Street/Fenn Street intersections, 30-40% of accidents occurred during nighttime. These nighttime accident rates are high in comparison to other intersections in the area. Therefore, the adequacy of street lighting should be checked. All signs should be checked to verify that retroreflectivity is adequate for nighttime.
•
At the Fenn Street/First Street intersection, inadequate corner sight distance for eastbound traffic on Fenn Street makes RTOR unsafe. There have been several angle accidents involving eastbound and southbound vehicles. Therefore, “NO TURN ON RED” sign should be installed for this approach.
•
At the Fenn Street/First Street intersection, turning radii for right turning vehicles from the southbound and eastbound approaches seem inadequate. As a result, many turning vehicles either encroach upon the opposing lane or come to a complete stop and make a sharp turn to get onto the correct receiving lane. Therefore, the possibility of increasing the turning radii or posting an appropriate speed limit for the southbound approach of First Street should be investigated.
•
At the Fenn Street/Second Street intersection, corner sight distance for RTOR vehicles from the westbound approach is insufficient. Off-street parking diminishes the visibility of oncoming traffic for RTOR vehicles. Therefore, right turns during red should be prohibited.
15
•
At the Fenn Street/Second Street intersection, the designated width for on-street parking on the eastbound approach of Fenn Street is inadequate. Therefore, either the prohibition of on-street parking or widening of available parking space should be considered.
•
At the Fenn Street/Second Street intersection, curb radius for vehicles turning right from the eastbound direction of Fenn Street should be increased to avoid potential conflicts with northbound traffic on Second Street.
•
At the Fenn Street/Second Street intersection, on-street parking on the right side of the westbound approach of Fenn Street reduces the visibility and maneuverability for vehicles entering from a driveway. Therefore, on-street parking should not be allowed beyond that driveway (towards intersection). Instead, there is adequate space to provide on-street parking on the left side on the same approach.
•
At the Fenn Street/Fourth Street intersection, there have been several angle accidents despite the presence of “NO TURN ON RED” signs on all approaches. The adequacy of yellow period and the tendency for repeated violation of traffic signals should be checked. Some of these accidents have occurred during nighttime. Therefore, street lighting should be examined for adequacy.
•
At the Fenn Street/Fourth Street intersection, three rear-end accidents have occurred when the pavement was either wet or icy. Therefore, the friction of road surface (or drainage) on all approaches should be checked. Another suggestion is improved snow removal during winter.
16
Appendix 1: Figures
Figure 1: Accidents by year 14
Fenn/First Fenn/Second Fenn/Fourth
12
Accidents per year
10
8
6
4
2
0 1998
1999
2000
2001
Year
17
Figure 2: Types of accidents 80%
70%
60%
Angle Rearend Other
Percentage
50%
40%
30%
20%
10%
0% Fenn/First
Fenn/Second
Fenn/Fourth
Location
18
Figure 3: Road surface 90%
80%
70%
Percentage
60% Dry Wet Snowy Icy
50%
40%
30%
20%
10%
0% Fenn/First
Fenn/Second
Fenn/Fourth
Location
19
Figure 4: Lighting condition 80% Daylight Dark[Road Lit] Dawn or Dusk
70%
60%
Percentage
50%
40%
30%
20%
10%
0% Fenn/First
Fenn/Second
Fenn/Fourth
Location
20
Figure 5: Accident Severity 20
Fatal Injury PDO
Number of accidents
15
10
5
0 Fenn/First St.
Fenn/Second St.
Fenn/Fourth St.
Location
21
Appendix 2: Collision Diagrams
22
23
24
Appendix 3: Accident Rate Formula Accident rate and critical accident rate calculations for the Fenn Street/ First Street intersection. Accident rate Accidents per MEV
= number of accidents during N years × 1 million 24-hour intersection entering volume × 365 × N = (30×1,000,000)/ ((4,500+18,000) ×365×4) (N = 4 years) = 0.91 accidents/MEV
Critical accident rate (RC) RC = (RA + K*(RA/M)1/2 – (1/2)*(1/M)) Where RA = Average accidents per million vehicles for similar types of intersections. = 0.65 accidents/MEV (for District 1, signalized intersections) M = Vehicles entering the intersection for one year in millions. = ((4600 + 18000) ×365)/ (1000000) = 8.21 MV. K = The value obtained from the cumulative standard normal distribution conversion table, based on the confidence interval value. = 1.645 (For 95% confidence interval) RC = 0.65 + 1.645× (0.65/8.21)1/2 – (1/2) × (1/8.21) = 1.05 accidents/million vehicles. Since accident rate (0.91 accidents/MEV) is less than RC (1.05 accidents/MEV), this intersection is not a high accident location.
25
First St.
Appendix 5: Condition Diagrams
Drive way
Private property
Private property
Fenn St.
X Walk
Fenn St.
X Walk
alk XW
Parking lot
First St.
Private property
Drive way
X Walk
Legend Tree Electric pole
No parking sign Signal Plantation Path way
Condition diagram
North
Fenn Street & First Street
32
Second St. Private property
Parking Lot
k X Wal
Shoulder
Shoulder
X Walk
X Walk
Fenn St Fenn St Shoulder X Walk
Parking Lot
Second St.
Post Office
Condition diagram Fenn Street & Second Street
Legend
North
Tree Electric pole
Plantation Path way
No parking sign
Drive way
33
Drive way
Fourth St.
Drive way
Private property
Private property
Fenn St.
Fenn St.
X Walk
X Walk
X Walk
X Walk
Private property Private property Parking
Legend
Fourth St.
Tree Electric pole No parking sign
Signal
Stop Sign Plantation Path way
Condition diagram
North
Fenn Street & Fourth Street
34
December 2004 Berkshire Regional Planning Commission 1 Fenn Street, Suite 201 Pittsfield, MA 01201
Funded by Federal Highway Administration, through Massachusetts Highway Department, for the Berkshire Metropolitan Planning Organization
Executive Summary The 2003 Regional Transportation Plan recommends a safety evaluation for intersections along Fenn Street in Pittsfield. Accordingly, the Berkshire Regional Planning Commission performed a safety study in June, 2004. This analysis focused on three main intersections along Fenn Street: First Street, Second Street and Fourth Street (see Locus Map). All three intersections are controlled by traffic signals. The well-accepted intersection safety improvement methods were utilized for the study. First, records of accidents that occurred at these intersections from 1998 to 2001 were analyzed to identify high accident types and patterns. Thereafter, an on-site observation study was conducted. Finally, the countermeasures for safety problems were developed. The Fenn Street/First Street intersection had the highest number of accidents, but the Fenn Street/Fourth Street intersection had the highest accident rate. Right angle accidents were the predominant pattern at these intersections. Between 30-40% of accidents at First Street/Fenn Street and Fourth Street/Fenn Street occurred during nighttime. Therefore, the adequacy of street lighting and nighttime visibility of signs should be checked. The corner sight distance is inadequate for vehicles turning right from the eastbound approach of the Fenn Street/First Street intersection and from the westbound approach of the Fenn Street/Second Street intersection. Therefore, “NO TURN ON RED” signs should be installed on those two approaches. The turning radii were found to be inadequate on many approaches to the intersections. At the First Street/Fenn Street intersection, due to the inadequacy of turning radius, vehicles turning right from the southbound approach to Fenn Street were seen coming to a complete stop before turning. This unexpected and sudden slow-down of turning vehicles gives rise to an increased risk of rear-end collisions. Since right-of-way limitations make increasing curb-radius difficult, the approach speed of First Street should be reduced. At the Fenn Street/Second Street intersection, the designated width for on-street parking on the eastbound approach of Fenn Street is inadequate. Therefore, either the prohibition of on-street parking on this approach or widening of available parking space should be considered. At the same intersection, on-street parking on the right side of the westbound approach reduces the visibility and maneuverability for vehicles entering from a nearby driveway. Therefore, on-street parking should not be allowed beyond that driveway (towards intersection). Instead, there is adequate space to provide on-street parking on the left side on the same approach. At the Fenn Street/Fourth Street intersection, three rear-end accidents have occurred when the pavement was either wet or icy. Therefore, road surface friction and adequacy of crown for drainage on all approaches should be checked. At the same intersection, there have been several angle accidents despite the presence of “NO TURN ON RED” signs on all approaches. The adequacy of yellow period and the tendency for repeated violation of traffic signals should be checked.
ii
Table of Contents
Executive Summary ............................................................................................................ ii 1.0 Introduction............................................................................................................. 1 2.0 Analysis................................................................................................................... 1 2.1 Accident trends ................................................................................................... 1 2.2 Accident types..................................................................................................... 3 2.3 Accidents by road surface condition................................................................... 3 2.4 Accidents by lighting condition .......................................................................... 4 2.5 Severity of accidents ........................................................................................... 4 2.6 Accident rates...................................................................................................... 4 2.7 Pedestrian and bicycle accidents......................................................................... 6 2.8 Cost of accidents ................................................................................................. 7 2.9 Summary of analysis........................................................................................... 7 3.0 Collision Diagrams ................................................................................................. 8 3.1 Fenn Street/First Street ....................................................................................... 8 3.2 Fenn Street/Second Street ................................................................................... 8 3.3 Fenn Street/Fourth Street .................................................................................... 8 4.0 On-Site Observations .............................................................................................. 9 4.1 Fenn Street/First Street ....................................................................................... 9 4.2 Fenn Street/Second Street ................................................................................. 11 4.3 Fenn Street/Fourth Street .................................................................................. 13 5.0 Condition Diagrams .............................................................................................. 14 6.0 Conclusions........................................................................................................... 15 Appendix 1: Figures.......................................................................................................... 17 Appendix 2: Collision Diagrams ...................................................................................... 22 Appendix 3: Accident Rate Formula ................................................................................ 25 Appendix 4: On-site Observation Sheets.......................................................................... 26 Appendix 5: Condition Diagrams ..................................................................................... 32
iii
1.0
Introduction
The 2003 Regional Transportation Plan (RTP) recommends a safety evaluation for intersections along Fenn Street. Accordingly, the Berkshire Regional Planning Commission (BRPC) performed a safety study in 2004. The results of the study are presented in this report. The findings of this study will form the basis for a future detailed study undertaken by a consultant to design safety improvements and for implementation. 1.1
Study area
This analysis focused on three main intersections along Fenn Street: First Street, Second Street and Fourth Street (see Locus Map). All three intersections are controlled by traffic signals. East Street and North Street intersections, which are located at the east and west ends of Fenn Street, were not considered. Both East Street and North Street are four-lane roads, which were (or will be) subjected to operational and geometric changes (e.g., road widening and alignment of East Street, on-street parking and signal improvements on North Street). Therefore, these two intersections were excluded from the analysis. The minor intersections along the corridor, such as Allen Street and Third Street were not considered as these intersections experience very few accidents. The approximate length of Fenn Street from North Street to East Street is 0.62 miles. 2.0
Analysis
The standard accident data analysis methods were used in this evaluation. While the RTP diagnoses were based on the 1990-97 accident data, this analysis utilized 1998-2001 accident data provided by the Massachusetts Highway Department. Data analysis was performed in several ways to identify safety problems: • Accident trends • Accident types • Road surface condition • Lighting condition • Severity of accidents • Accident rates • Pedestrian and bicycle accidents • Cost of accidents 2.1
Accident trends
Refer to Table 1 and Figure 1 in Appendix 1 for numbers of accidents reported at these intersections from 1998 to 2001. The Fenn Street/First Street intersection reported the highest number of accidents; the Fenn Street/Second Street intersection reported the least number of accidents. However, since 1999, the number of accidents occurred at the Fenn Street/Second Street intersection has remained unchanged (i.e., no reduction).
1
Locus Map
4 0
125 250
Fourt h
>
> Fenn S
East
S tr e e
500 Feet
Stree t
Seco nd St reet
North Stree t
First Stree t
Rail line
> tr e e t
s Ea
t tS
re
et
t
Pittsfield
2
An interesting observation is the very high numbers of accidents at Fenn Street/Fourth Street (in 1998) and at Fenn Street/First Street (in 2000) and sharp decline in accidents in the following year. It appears Fenn Street/ Fourth Street has been able to maintain a relatively low accident rate since the high accident occurrence in 1998. The same cannot be said with certainty about Fenn Street/ First Street due to lack of data for sufficient numbers of “after peak” years. Table 1: Accidents on intersections along Fenn Street Fenn/ First
Year
2.2
Fenn/Second
Fenn/ Fourth
Number
Percentage
Number
Percentage
Number
Percentage
1998
8
27%
1
7%
10
48%
1999
6
20%
4
31%
3
14%
2000
13
43%
4
31%
3
14%
2001
3
10%
4
31%
5
24%
Total
30
100%
13
100%
21
100%
Accident types
As indicated in Table 2 and Figure 2 in Appendix 1, right angle accidents are the predominant pattern at all these intersections. The probable causes for right angle accidents at signalized intersections are restricted sight distance, high approach speed, and inadequate signal timing or type of signals. The general countermeasures include removal of sight obstructions, restriction of parking near corners, installation of warning signs, adjustment of yellow interval, etc. This study will attempt to identify pertinent countermeasures for these intersections. Please refer to collision diagrams presented in Appendix 2 for more information on accident types and related patterns. Table 2: Accidents by type Fenn/ First
Type
2.3
Fenn/Second
Fenn/ Fourth
Number
Percentage
Number
Percentage
Number
Percentage
Angle
19
63%
9
69%
14
67%
Rear end
5
17%
3
23%
3
14%
Other
6
20%
1
8%
4
19%
Accidents by road surface condition
Table 3 and Figure 3 in Appendix 1 indicate that majority of the accidents occurred when the pavement was dry. In general, percentage distribution of road surface conditions at the times of accidents at intersections is similar. Therefore, no particular road surface conditions contributory to high accidents were identified.
3
Table 3: Accidents by road surface Fenn/ First
Surface
2.4
Fenn/Second
Fenn/ Fourth
Number
Percentage
Number
Percentage
Number
Percentage
Dry
21
70%
10
77%
16
76%
Wet
5
17%
2
15%
3
14%
Snowy
1
3%
0
0%
0
0%
Icy
2
7%
1
8%
2
10%
Accidents by lighting condition
Table 4 and Figure 4 in Appendix 1 indicate that most accidents occurred during daytime. However, the nighttime accident rates at First Street/Fenn Street and First Street/Fourth Street intersections are high. The most likely reason for nighttime accidents is poor visibility. The general countermeasures include improving street lighting, installation of reflectorized signs and pavement markings, and removal of distracting commercial lighting and other sources of glare. The field visit will investigate the contributory factors for nighttime accidents. Table 4: Accidents by lighting condition Fenn/ First
Type
2.5
Fenn/Second
Fenn/ Fourth
Number
Percentage
Number
Percentage
Number
Percentage
Daylight
19
63%
9
69%
13
62%
Dark[Road Lit]
10
33%
3
23%
8
38%
Dawn or Dusk
0
0%
1
8%
0
0%
Severity of accidents
Table 5 and Figure 5 in Appendix 1 break down accidents by severity. As seen from Figure 5, there have been no fatal accidents. The ratio of injury accidents to property damage only (PDO) is high. In particular, 60 percent of accidents at First Street/Fenn Street have resulted in injuries. The types of accidents that resulted injuries will be analyzed using collision diagrams (section 3.1). Table 6: Accidents by severity Fenn/ First
2.6
Fenn/Second
Fenn/ Fourth
Fatal
Injury
PDO
Fatal
Injury
PDO
Fatal
Injury
PDO
0
18
12
0
7
6
0
10
11
Accident rates
A commonly used method for identifying high accident intersections is to compare accident rates with average area-wide accident rates. The rate used in this analysis is accidents per million entering vehicles (MEV). The accident rate formula is given below.
4
Accidents per MEV
=
number of accidents in one year X 1 million 24-hour intersection entering volume X 365
Tables 7-9 give accident rates for the intersections along Fenn Street. The estimated values were used when Average Daily Traffic (ADT) data were not available. Table 7: Fenn Street and First Street (signals) Year
ADT Fenn Street
ADT First Street
1998
4,500
18,000
8.21
8
1999
4,500
18,000
8.21
6
2000
4,500
18,000
8.21
13
2001
4,500
18,000
8.21
3
32.84
30
Total
MEV
Accidents
Accident rate is 0.91 per MEV. Table 8: Fenn Street and Second Street (signals) Year
ADT Fenn Street
ADT Second Street
1998
4,500
2,800
2.66
1
1999
4,500
2,800
2.66
4
2000
4,500
2,800
2.66
4
2001
4,500
2,800
2.66
4
10.64
13
Total
MEV
Accidents
Accident rate is 1.22 per MEV. Table 9: Fenn Street and Fourth Street (signals) Year
ADT Fenn Street
ADT Fourth Street
1998
4,500
4,500
3.29
10
1999
4,500
4,500
3.29
3
2000
4,500
4,500
3.29
3
2001
4,500
4,500
3.29
5
13.16
21
Total
MEV
Accidents
Accident rate is 1.60 per MEV. The values given in Table 10 represent average accident rates for signalized and unsignalized intersections for 2002.
5
Table 10: Average accident rates (accidents per MEV) Location
Signalized intersections
Unsignalized intersections
Statewide
0.87
0.66
0.65
0.34
District 1 Source: MassHighway
Table 11 summarizes accident rates, comparative area-wide average accident rates, and critical accident rates for the intersections. The critical accident rate (RC) is used to determine if an intersection is a high accident location or not. If the accident rate at an intersection is greater than the critical accident rate, that intersection is considered as a high accident location. The interpretation of a high accident location can be phrased as “We are 95% confident that the intersection is a high accident location, based on its accidents, traffic volume, and comparative area-wide average accident statistics.” The formulae used for the critical accident rates presented in Table 11 and a sample calculation is given in Appendix 3. Table 11: Comparison of accident rates against average rates for District 1 Average rate for District 1 (per MEV)
RC
Ratio of accident rate/RC
0.91
0.65
1.05
0.87
Fenn Street/ Second Street
1.22
0.65
1.27
0.96
Fenn Street/ Fourth Street
1.60
0.65
1.23
1.30
Location Fenn Street/ First Street
Accident rate (per MEV)
In comparison to average accident rates for MassHighway District 1, the three intersections have above-average accident rates. However, based on the critical accident rate, only Fenn Street/Fourth Street can be treated as a high accident location. Fenn Street/First Street, which has the highest number of accidents, is not identified as a high accident location because of the large volume of traffic that passes through the intersection daily. Based on the findings of the analyses presented in sections 2.1-2.6 (e.g., severity of accidents, lighting condition, accident rate, etc), the three intersections will be analyzed further using field data. 2.7
Pedestrian and bicycle accidents
As indicated in Table 12, pedestrian and bicycle accidents are rare. The availability of push buttons at signalized intersections and paved sidewalks may be contributory for low pedestrian and bicycle accidents. However, this study will investigate possible measures for further improving safety for pedestrians and bicyclists.
6
Table 12: Pedestrian and bicycle accidents
2.8
Fenn St/ First St
Fenn St/ Second St
Year
Pedestrian
Bicycle
Pedestrian
Bicycle
Pedestrian
Fenn St/ Fourth St Bicycle
1998
0
0
0
0
0
0
1999
0
0
0
1
1
0
2000
1
0
0
0
0
1
2001
0
0
0
0
0
0
Total
1
0
0
1
1
1
Cost of accidents
The approximate cost of accidents was estimated using the Federal Highway Administration’s (FHWA) cost data. The purpose of calculating accident costs is to emphasize the severity of safety problems and thereby highlight the need for remedial measures. Table 13 presents costs developed by FHWA using 1994 dollar values. Table 13: Cost of accidents by severity (FHWA) Descriptor Fatal Incapacitating
Cost (1994) $2,600,000 $180,000
Injury evident
$36,000
Injury possible
$19,000
Property damage only
$2,000
Since the traffic accident reports do not specify the level of injury, an injury accident was assumed to cost $27,500 (average of injury evident and injury possible values). Based on the accident severity data presented in Table 6, costs of accidents at these intersections were estimated (Table 14). Fenn Street/First Street reported the highest cost due to its high number of injury accidents. Table 14: Cost of accidents 1998-2001 Location
2.9
Cost (1994 dollars)
Fenn Street/ First Street
$519,000
Fenn Street/ Second Street
$204,500
Fenn Street/ Fourth Street
$297,000
Summary of analysis
The main findings of accident data analysis include: • Fenn Street/First Street intersection has the highest number of accidents. • Right angle accidents are the predominant pattern at all intersections.
7
• • • • • 3.0
The percentage of nighttime accidents at Fenn Street/First Street and Fourth Street/Fenn Street is very high. Sixty percent of accidents occurred at Fenn Street/First Street intersection have resulted in personal injuries; the injury accident rate at the other two intersections is between 45-55 percent. The accident rates at the three intersections are higher than the area-wide annual accident rates. However, based on critical accident rate methodology, only Fenn Street/Fourth Street is identified as a high accident location. High percentages of severe accidents, nighttime accidents and above-average accident rate warrant further analysis of these intersections using field data. Pedestrian and bicycle accidents are few. Collision Diagrams
Collision diagrams are used to display and identify accident patterns. They provide information such as approximate location, type of accidents, time of day, weather, and pavement conditions that are helpful for identifying probable causes for accidents. Collision diagrams for all four intersections are attached in Appendix 2. Some of the patterns visualized by collision diagrams (type of accidents, severity, etc) were discussed previously. Other notable patterns observed from collision diagrams for each intersection are described in sections 3.1-3.3. 3.1
Fenn Street/First Street
Right-angle accidents, which are the prevalent accidents on this intersection (63 percent), are equally spread at all four intersecting approaches. The majority of right angle accidents resulted in injuries. There have been five rear end accidents, four of them involving vehicles on First Street. Notably, four out of five rear-end accidents resulted in injuries. Probable reasons for rear-end accidents at this intersection are inadequate signal timing and large volume of turning vehicles. There have been three left turn accidents. These left turn accidents can be attributed to permitted left turns at the intersection. 3.2
Fenn Street/Second Street
The majority of right angle accidents have occurred between northbound traffic on Second Street and westbound traffic on Fenn Street. Another revelation from the collision diagram is that all accidents involving southbound traffic resulted in injuries. Two of the three rear-end accidents were involving southbound vehicles. There has been one bicycle accident. 3.3
Fenn Street/Fourth Street
Southbound traffic on Fourth Street involved in majority (57 percent) of the reported accidents. Moreover, the majority of right angle accidents were involving southbound vehicles with eastbound and westbound vehicles. There have been one reported rear-
8
accident on each direction, and three of these four accidents have occurred when the pavement was wet or icy. 4.0
On-Site Observations
To investigate physical characteristics of the intersections and to identify probable causes for accidents, the study team made a site visit on 30th June, 2004. First, the observers drove though each intersection several times from all possible approaches. Thereafter, the driver behavior at the intersections was observed. Next, an “On-Site Observation Report” was completed for each intersection (see Appendix 4). This was followed by physical measurements of intersections and taking digital photographs. The following sections describe the main observations of the field visit. 4.1
Fenn Street/First Street
This intersection is fairly busy during daytime. There are dense roadside developments, except at the southeast corner of the intersection. Therefore, right turns on red periods (RTOR) are not allowed from the westbound approach of Fenn Street. As seen from Photo 1, the sight distance for RTOR from the eastbound approach of Fenn Street is inadequate (view impeded by a building at the northwest corner). Moreover, five accidents have occurred between eastbound and southbound vehicles. Therefore, RTOR for eastbound vehicles should not be allowed.
Photo 1: View looking north from eastbound stop line on Fenn Street
The turning radii for right turning vehicles from the southbound and eastbound approaches seem inadequate. As a result, many turning vehicles either encroach upon the
9
opposing lane (of the receiving approach) or come to a complete stop and make a sharp turn to get onto the correct receiving lane. In the absence of a separate right turn lane, vehicles having to stop and turn during green time greatly reduces the number of vehicles that can pass through the intersection. Moreover, this gives rise to the risk of rear end collisions between turning vehicles and through vehicles. Therefore, the possibility of increasing turning radii should be investigated (without unduly increasing walking distance for pedestrians). If the available right-of-way restricts any geometric improvements, an alternative suggestion is to post an appropriate speed limit on the southbound approach of First Street (presently, there are no speed limit signs). A reduced approach speed limit, which is consistent with the existing speed limits for urban settings, should help to minimize the risk of rear end accidents between turning vehicles and through vehicles. The stop line on the southbound approach of First Street has been shifted about 20 feet away from the pedestrian crossing (Photo 2). This might have been done due to the inadequacy of curb radius for trucks turning right onto First Street to travel north from the westbound approach of Fenn Street. There are two conceivable drawbacks of this layout: reduced storage capacity of left turn lane on the southbound approach, and increased distance that a stopped vehicle on the southbound approach has to travel to clear the intersection during green time. If curb radius is increased to accommodate truck turns, it would result in a longer walking distance for pedestrians crossing at this location. Unless a way to reroute trucks can be found, the above-mentioned drawbacks will prevail at this intersection.
Photo 2: Separation between pedestrian crossing and stop line
10
The road surface of the eastbound approach of Fenn Street lacks proper crown. As a result, during rain, water doesn’t drain away from the road surface. To improve this situation, this approach should be resurfaced. A driveway is located about 50 feet north of the intersection off First Street. This driveway provides access to few parking spaces. However, vehicles entering and exiting from this driveway interfere with the queue storage area of southbound traffic on Fenn Street. Therefore, the possibility of closing this driveway and providing an alternative access to the parking spaces should be considered. 4.2
Fenn Street/Second Street
This is a signalized four-way intersection with a relatively low traffic volume in comparison to the previously discussed intersection. However, RTOR vehicles from the westbound approach appear to have insufficient corner sight distance (Photo 3). Offstreet parking diminishes the visibility of oncoming traffic for RTOR vehicles from the westbound approach. Therefore, right turns during red should be prohibited.
Photo 3: View looking south from westbound approach of Fenn Street
The turning radius for vehicles turning right from Fenn Street eastbound direction is inadequate. As a result, these vehicles encroach upon the opposing traffic lane of the northbound approach. Therefore, the curb radius at the southwest quadrant should be increased to facilitate right turns. On-street parking is allowed on the right side of the eastbound approach of Fenn Street. However, the designated width of the parking lane is only 2 feet (Photo 4). Any vehicle parking in these spaces reduces the effective travelway width for westbound traffic. 11
Therefore, either the prohibition of on-street parking or widening of available parking space should be considered. On-street parking is allowed on the right side of the westbound approach of Fenn Street. However, an access driveway is located within the designated parking area (Photo 5). Therefore, on-street parking should not be allowed beyond this driveway (towards intersection). Any parked vehicle beyond the driveway reduces sight distance and maneuverability of vehicles entering Fenn Street from that driveway. Instead, there is adequate space to provide on-street parking on the other side of the street. Therefore, if necessary, on-street parking can be allowed on that side.
Parking sign
Photo 4: Inadequate on-street parking space on eastbound approach of Fenn Street
12
Driveway Parking
Photo 5: Conflict between parking layout and driveway location on Fenn Street
4.3
Fenn Street/Fourth Street
This is a four-way signalized intersection. It has the highest accident rate among the three intersections. The eastbound approach of Fenn Street has a downgrade about 3-5 % (Photo 6). However, there have been only one reported rear-end accident on that approach. Moreover, the other three approaches have also recorded one rear-end accident during the same period. Most these accidents occurred on wet or icy pavements. Therefore, accidents do not show a correlation with the slope of the eastbound approach. Instead, friction of the road surface of all approaches should be checked. Another suggestion is the proper snow removal during winter.
13
Photo 6: Downgrade on eastbound Fenn Street approaching Fourth Street
In general, corner sight distances are inadequate. However, “NO TURNS ON RED” signs are present on all approaches. There seems to be adequate signage to alert drivers to the lack of corner sight distance, and thereby prevent risky RTOR. In spite of the signage, there have been several angle accidents at the southeast and southwest corners. Therefore, the other possible contributory factors to angle accidents such as inadequate yellow interval and repeated driver violations of traffic signals should be investigated. The street lighting appears somewhat inadequate (based on the number of street lights available). As Table 4 indicates, 38% of accidents have occurred during nighttime. At least five angle accidents have occurred during nighttime. It may be possible that during nighttime, traffic signals turn into flashing yellow/red mode. In the absence of signals, inadequate nighttime visibility may compound the right-of-way sharing difficulties for drivers. Therefore, the possibility of improving street lightings and/or installation of retroreflectorized signs should be explored. On-street parking is allowed on one side of Fenn Street. While parking maneuvers can give rise to conflicts, accident records indicate only one accident that involved a parked vehicle. Therefore, on-street parking does not appear to be a primary reason for accidents. 5.0
Condition Diagrams
Based on the measurements taken of the roadway and immediate surroundings, condition diagrams were prepared for each intersection. Condition diagrams were prepared as scaled drawings and these are helpful for relating accident patterns and probable causes to the physical features on and near the roadway. Appendix 5 presents the condition
14
diagrams and these diagrams can also be used when developing detailed safety improvements.
6.0
Conclusions
The safety of three intersections along Fenn Street (First Street, Second Street and Fourth Street) was evaluated. These are four-way signalized intersections. To identify safety problems and to recommend countermeasures, the study team followed a well-established accident evaluation methodology, which included an analysis of crash data, field visits, and preparation of collision and condition diagrams. The accidents reported between 1998 and 2001 were used in the analysis. The main findings of the study include: • The accident rates at all three intersections are higher than the District 1 area-wide average accident rates. •
Fenn Street/First Street experienced the highest number of accidents during this period. However, due to higher number of accidents in comparison to traffic volume passing the intersection, only Fourth Street/Fenn Street is identified as a high accident location.
•
Right angle accidents are the predominant pattern at these intersections. Moreover, at First Street/Fenn Street and Fourth Street/Fenn Street intersections, 30-40% of accidents occurred during nighttime. These nighttime accident rates are high in comparison to other intersections in the area. Therefore, the adequacy of street lighting should be checked. All signs should be checked to verify that retroreflectivity is adequate for nighttime.
•
At the Fenn Street/First Street intersection, inadequate corner sight distance for eastbound traffic on Fenn Street makes RTOR unsafe. There have been several angle accidents involving eastbound and southbound vehicles. Therefore, “NO TURN ON RED” sign should be installed for this approach.
•
At the Fenn Street/First Street intersection, turning radii for right turning vehicles from the southbound and eastbound approaches seem inadequate. As a result, many turning vehicles either encroach upon the opposing lane or come to a complete stop and make a sharp turn to get onto the correct receiving lane. Therefore, the possibility of increasing the turning radii or posting an appropriate speed limit for the southbound approach of First Street should be investigated.
•
At the Fenn Street/Second Street intersection, corner sight distance for RTOR vehicles from the westbound approach is insufficient. Off-street parking diminishes the visibility of oncoming traffic for RTOR vehicles. Therefore, right turns during red should be prohibited.
15
•
At the Fenn Street/Second Street intersection, the designated width for on-street parking on the eastbound approach of Fenn Street is inadequate. Therefore, either the prohibition of on-street parking or widening of available parking space should be considered.
•
At the Fenn Street/Second Street intersection, curb radius for vehicles turning right from the eastbound direction of Fenn Street should be increased to avoid potential conflicts with northbound traffic on Second Street.
•
At the Fenn Street/Second Street intersection, on-street parking on the right side of the westbound approach of Fenn Street reduces the visibility and maneuverability for vehicles entering from a driveway. Therefore, on-street parking should not be allowed beyond that driveway (towards intersection). Instead, there is adequate space to provide on-street parking on the left side on the same approach.
•
At the Fenn Street/Fourth Street intersection, there have been several angle accidents despite the presence of “NO TURN ON RED” signs on all approaches. The adequacy of yellow period and the tendency for repeated violation of traffic signals should be checked. Some of these accidents have occurred during nighttime. Therefore, street lighting should be examined for adequacy.
•
At the Fenn Street/Fourth Street intersection, three rear-end accidents have occurred when the pavement was either wet or icy. Therefore, the friction of road surface (or drainage) on all approaches should be checked. Another suggestion is improved snow removal during winter.
16
Appendix 1: Figures
Figure 1: Accidents by year 14
Fenn/First Fenn/Second Fenn/Fourth
12
Accidents per year
10
8
6
4
2
0 1998
1999
2000
2001
Year
17
Figure 2: Types of accidents 80%
70%
60%
Angle Rearend Other
Percentage
50%
40%
30%
20%
10%
0% Fenn/First
Fenn/Second
Fenn/Fourth
Location
18
Figure 3: Road surface 90%
80%
70%
Percentage
60% Dry Wet Snowy Icy
50%
40%
30%
20%
10%
0% Fenn/First
Fenn/Second
Fenn/Fourth
Location
19
Figure 4: Lighting condition 80% Daylight Dark[Road Lit] Dawn or Dusk
70%
60%
Percentage
50%
40%
30%
20%
10%
0% Fenn/First
Fenn/Second
Fenn/Fourth
Location
20
Figure 5: Accident Severity 20
Fatal Injury PDO
Number of accidents
15
10
5
0 Fenn/First St.
Fenn/Second St.
Fenn/Fourth St.
Location
21
Appendix 2: Collision Diagrams
22
23
24
Appendix 3: Accident Rate Formula Accident rate and critical accident rate calculations for the Fenn Street/ First Street intersection. Accident rate Accidents per MEV
= number of accidents during N years × 1 million 24-hour intersection entering volume × 365 × N = (30×1,000,000)/ ((4,500+18,000) ×365×4) (N = 4 years) = 0.91 accidents/MEV
Critical accident rate (RC) RC = (RA + K*(RA/M)1/2 – (1/2)*(1/M)) Where RA = Average accidents per million vehicles for similar types of intersections. = 0.65 accidents/MEV (for District 1, signalized intersections) M = Vehicles entering the intersection for one year in millions. = ((4600 + 18000) ×365)/ (1000000) = 8.21 MV. K = The value obtained from the cumulative standard normal distribution conversion table, based on the confidence interval value. = 1.645 (For 95% confidence interval) RC = 0.65 + 1.645× (0.65/8.21)1/2 – (1/2) × (1/8.21) = 1.05 accidents/million vehicles. Since accident rate (0.91 accidents/MEV) is less than RC (1.05 accidents/MEV), this intersection is not a high accident location.
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First St.
Appendix 5: Condition Diagrams
Drive way
Private property
Private property
Fenn St.
X Walk
Fenn St.
X Walk
alk XW
Parking lot
First St.
Private property
Drive way
X Walk
Legend Tree Electric pole
No parking sign Signal Plantation Path way
Condition diagram
North
Fenn Street & First Street
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Second St. Private property
Parking Lot
k X Wal
Shoulder
Shoulder
X Walk
X Walk
Fenn St Fenn St Shoulder X Walk
Parking Lot
Second St.
Post Office
Condition diagram Fenn Street & Second Street
Legend
North
Tree Electric pole
Plantation Path way
No parking sign
Drive way
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Drive way
Fourth St.
Drive way
Private property
Private property
Fenn St.
Fenn St.
X Walk
X Walk
X Walk
X Walk
Private property Private property Parking
Legend
Fourth St.
Tree Electric pole No parking sign
Signal
Stop Sign Plantation Path way
Condition diagram
North
Fenn Street & Fourth Street
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