70676 Transport Engineering
CIV3703 Transport Engineering
Module 9 – Part 1
Traffic Studies and Parking
9.1 Purpose of Traffic Studies Traffic Study = collection and analysis of measurable factual data relating to traffic and its characteristics. Purpose: basis for planning and design assist traffic operation e.g., need for signs evaluate effects of changes (before and after) basic characteristics of traffic
Common Types of Traffic Studies traffic volume counts origin and destination studies speed studies travel time and delay studies crash studies parking studies
Other Traffic Studies axle load surveys lateral placement surveys goods movements surveys pedestrian surveys traffic access surveys traffic impact surveys
9.2 Traffic Volume Counts Number of vehicles past a point. Information sought: traffic volume and direction of traffic volume of turning traffic (intersections) hourly, daily, seasonal variations proportion of cars, trucks, etc.
Purposes of Volume Counts The purposes of the volume counts: To select pavement, shoulder and bridge widths pavement thickness design economic comparisons of alternatives need for control devices determine construction priorities scheduling roadway maintenance determine trends in growth design intersections determine accident rates plan road system validate origin and destination surveys general info.
9.2.1 Methods of Counting Manual short term counts turning movements, pedestrians, occupancy relatively expensive
Automatic non-recording, recording detectors (vehicles, axles) pneumatic tube loop
Use of overhead traffic detectors
Source: Garber, N.J. & Hoel, L.A. 2009, Traffic and Highway Engineering, Cengage Learning, Stamford, USA.
Use of overhead detectors
Source: Garber, N.J. & Hoel, L.A. 2009, Traffic and Highway Engineering, Cengage Learning, Stamford, USA.
9.2.2 Presentation of Results Tabular, graphical Hourly volumes
Intersection flow counts
Traffic volume with growth rates Network with bands proportional to flow.
Example of a Traffic Flow Map Network with bands proportional to flow.
Source: Garber, N.J. & Hoel, L.A. 2009, Traffic and Highway Engineering, Cengage Learning, Stamford, USA.
9.3 Origin and Destination Surveys Indicate travel desires - origin and destination Generally used for planning of transport facilities Location, design and programming of new or improved highways, public transport, and parking facilities
Survey type depends on area and data required
9.3.1 Methods of Conducting O-D Surveys Recording registration numbers non-interfering large number of personnel required Observers at the point entry and exit
limited O-D information busy sites use random sampling
Techniques used Last two/three digits of the registration numbers, depending on the size of sample required. Match the records to determine the journey time Upper limit for the journey time can be set to discard the stopped vehicles
Handing postcards to drivers vehicles need to be stopped - police required stoppages minimal Questions limited to five or six low response rates – bias Different colour can be used for indentify the location of the survey point or different directions of travel 20% return is considered essential to improve accuracy Advanced publicity is necessary to ensure public cooperation
Roadside Interview vehicles stopped - police required more complete information unbiased sample considerable delay to motorists
Techniques used Appropriate signs on the approaches to the survey point are required Effort must be to avoid congestion Random sample Interviews are carried out on traffic entering and leaving a cordon line
Tag on Vehicle Survey vehicles stopped - tag attached limited information
Headlight Survey drivers asked to switch on headlights limited information bias
Home Interview Survey used to give broader road travel demand picture random sample used - 5 to 20 % complete information collected expensive and time consuming
Information to be collected number and kinds of vehicles owned, number of persons, sex, race, occupation, industry, number of trips made by each person, purpose of trip, original starting point and ultimate destination for each trip, mode of transportation employed, and the time of day during which each trip was made. Data regarding parking of private passenger vehicles may also be collected.
9.3.2 Presentation of Results Generally pictorial presentation flow diagrams desire line diagrams.
Tabular and graphical information
9.4 Speed studies Purposes of the speed studies are: to determine the range and magnitude of speeds as a basis for formulating design standards to find a correlation between speeds and crashes or between speeds and geometric features to determine the need for traffic control devices, including speed zoning to check the effectiveness of changes by conducting before and after studies economic analysis.
9.4 Speed Studies Methods • • • •
radar meters Ladar devices (laser) photographs of road section (aerial) timing vehicles
Results: • •
tables, graphs, diagrams mean speed, 85th percentile
Analysis and presentation of results
9.5 Travel Time and Delay Studies Modified form of speed study. Used in urban areas to determine congestion points.
9.5.1 Methods for Gathering Travel Time Data Licence plate method. Time and registration numbers of vehicles at points
Test car method. Car in flow at average speed (Driver + Observer)
Floating car methods Similar to test car (Driver + 2 Observers)
Arrival-output method. Test car with outside observers
9.5.2 Presentation of Results Tabular, graphical and diagrammatical form
Location and cause of delays identified. Time contour maps
Travel time - contour maps
9.6 Crash Studies Uses: identification of hazardous locations determining priorities for improvement evaluate safety improvements (before and after) measure of level of service research to determine crash causes
Information obtained from records of individual crashes. Data sources: police records insurance records public impressions.
Police data - limited fatal Serious injury property damage > $ 2500
Crash Data Required Basic data: type, result, date and time, precise location events prior to crash number and description of vehicles, road users environmental conditions: weather, lighting
Roadway data surface conditions geometrics
Traffic control devices
Info. generally recorded by ticking boxes precoded and not subject to bias may not suit particular situation.
Crashes may be recorded in manual or computerised system. Generally stored according to location.
Crash incident report form
9.6.1 Presentation of Crash Data Crash spot maps Map of area / road section All maps indicated by coloured dots / pins
Collision Diagrams Particular intersection All crashes for specific period (eg year)
Crash summary form Recommended when routine crash histories are required
A typical crash spot map - Toowoomba
The Chronicle 11 September 2004
Definitions for coding accidents
9.6.2 Uses of Crash Data Identification of hazardous locations Priority order for remedial actions established.
Crash costs Used for establishing economic viability of changes.
Evaluation studies Before and after studies.
9.6.3 Road Safety Audits A formal examination of an existing or future road, or traffic project in which an independent, qualified examiner looks at the project’s crash potential and / or safety performance.
Objectives of a road safety audit minimise the risk and severity of road crashes minimise the need for remedial work after construction reduce the whole-of-life costs of the project improve awareness of safe design practices. The essential elements of the process are: ● It is a formal process, not an informal one ● It is conducted by someone who is independent of the designer ● It is conducted by someone with appropriate experience and training ● It is restricted to road safety issues.
Application of Safety Audits Example: for a new road audit may be conducted at: • Feasibility stage • Layout or preliminary design stage • Detailed design stage • Pre-opening stage • In-service stage
9.7 Parking Studies Indicate: • Number and location of parking spaces; • Existing parking practices (duration, etc); • Need to vary time limits or install meters; • Adequacy of existing enforcement methods.
9.7.1 Methods for Parking Studies Select study area. Carry out inventory of defined area. Carry out a cordon count Carry out a parking usage study Survey of all parking spaces at regular intervals
Questionnaires
Typical inventory map
A typical observation sheet
9.7.2 Presentation of Results Tables, graphs and diagrams. Typical results: Variation in demand with time Variations in flow and vehicle accumulation Parking durations Compliance with regulations.
End Module 9, Part 1
Module 9 – Part 1
Traffic Studies and Parking
9.1 Purpose of Traffic Studies Traffic Study = collection and analysis of measurable factual data relating to traffic and its characteristics. Purpose: basis for planning and design assist traffic operation e.g., need for signs evaluate effects of changes (before and after) basic characteristics of traffic
Common Types of Traffic Studies traffic volume counts origin and destination studies speed studies travel time and delay studies crash studies parking studies
Other Traffic Studies axle load surveys lateral placement surveys goods movements surveys pedestrian surveys traffic access surveys traffic impact surveys
9.2 Traffic Volume Counts Number of vehicles past a point. Information sought: traffic volume and direction of traffic volume of turning traffic (intersections) hourly, daily, seasonal variations proportion of cars, trucks, etc.
Purposes of Volume Counts The purposes of the volume counts: To select pavement, shoulder and bridge widths pavement thickness design economic comparisons of alternatives need for control devices determine construction priorities scheduling roadway maintenance determine trends in growth design intersections determine accident rates plan road system validate origin and destination surveys general info.
9.2.1 Methods of Counting Manual short term counts turning movements, pedestrians, occupancy relatively expensive
Automatic non-recording, recording detectors (vehicles, axles) pneumatic tube loop
Use of overhead traffic detectors
Source: Garber, N.J. & Hoel, L.A. 2009, Traffic and Highway Engineering, Cengage Learning, Stamford, USA.
Use of overhead detectors
Source: Garber, N.J. & Hoel, L.A. 2009, Traffic and Highway Engineering, Cengage Learning, Stamford, USA.
9.2.2 Presentation of Results Tabular, graphical Hourly volumes
Intersection flow counts
Traffic volume with growth rates Network with bands proportional to flow.
Example of a Traffic Flow Map Network with bands proportional to flow.
Source: Garber, N.J. & Hoel, L.A. 2009, Traffic and Highway Engineering, Cengage Learning, Stamford, USA.
9.3 Origin and Destination Surveys Indicate travel desires - origin and destination Generally used for planning of transport facilities Location, design and programming of new or improved highways, public transport, and parking facilities
Survey type depends on area and data required
9.3.1 Methods of Conducting O-D Surveys Recording registration numbers non-interfering large number of personnel required Observers at the point entry and exit
limited O-D information busy sites use random sampling
Techniques used Last two/three digits of the registration numbers, depending on the size of sample required. Match the records to determine the journey time Upper limit for the journey time can be set to discard the stopped vehicles
Handing postcards to drivers vehicles need to be stopped - police required stoppages minimal Questions limited to five or six low response rates – bias Different colour can be used for indentify the location of the survey point or different directions of travel 20% return is considered essential to improve accuracy Advanced publicity is necessary to ensure public cooperation
Roadside Interview vehicles stopped - police required more complete information unbiased sample considerable delay to motorists
Techniques used Appropriate signs on the approaches to the survey point are required Effort must be to avoid congestion Random sample Interviews are carried out on traffic entering and leaving a cordon line
Tag on Vehicle Survey vehicles stopped - tag attached limited information
Headlight Survey drivers asked to switch on headlights limited information bias
Home Interview Survey used to give broader road travel demand picture random sample used - 5 to 20 % complete information collected expensive and time consuming
Information to be collected number and kinds of vehicles owned, number of persons, sex, race, occupation, industry, number of trips made by each person, purpose of trip, original starting point and ultimate destination for each trip, mode of transportation employed, and the time of day during which each trip was made. Data regarding parking of private passenger vehicles may also be collected.
9.3.2 Presentation of Results Generally pictorial presentation flow diagrams desire line diagrams.
Tabular and graphical information
9.4 Speed studies Purposes of the speed studies are: to determine the range and magnitude of speeds as a basis for formulating design standards to find a correlation between speeds and crashes or between speeds and geometric features to determine the need for traffic control devices, including speed zoning to check the effectiveness of changes by conducting before and after studies economic analysis.
9.4 Speed Studies Methods • • • •
radar meters Ladar devices (laser) photographs of road section (aerial) timing vehicles
Results: • •
tables, graphs, diagrams mean speed, 85th percentile
Analysis and presentation of results
9.5 Travel Time and Delay Studies Modified form of speed study. Used in urban areas to determine congestion points.
9.5.1 Methods for Gathering Travel Time Data Licence plate method. Time and registration numbers of vehicles at points
Test car method. Car in flow at average speed (Driver + Observer)
Floating car methods Similar to test car (Driver + 2 Observers)
Arrival-output method. Test car with outside observers
9.5.2 Presentation of Results Tabular, graphical and diagrammatical form
Location and cause of delays identified. Time contour maps
Travel time - contour maps
9.6 Crash Studies Uses: identification of hazardous locations determining priorities for improvement evaluate safety improvements (before and after) measure of level of service research to determine crash causes
Information obtained from records of individual crashes. Data sources: police records insurance records public impressions.
Police data - limited fatal Serious injury property damage > $ 2500
Crash Data Required Basic data: type, result, date and time, precise location events prior to crash number and description of vehicles, road users environmental conditions: weather, lighting
Roadway data surface conditions geometrics
Traffic control devices
Info. generally recorded by ticking boxes precoded and not subject to bias may not suit particular situation.
Crashes may be recorded in manual or computerised system. Generally stored according to location.
Crash incident report form
9.6.1 Presentation of Crash Data Crash spot maps Map of area / road section All maps indicated by coloured dots / pins
Collision Diagrams Particular intersection All crashes for specific period (eg year)
Crash summary form Recommended when routine crash histories are required
A typical crash spot map - Toowoomba
The Chronicle 11 September 2004
Definitions for coding accidents
9.6.2 Uses of Crash Data Identification of hazardous locations Priority order for remedial actions established.
Crash costs Used for establishing economic viability of changes.
Evaluation studies Before and after studies.
9.6.3 Road Safety Audits A formal examination of an existing or future road, or traffic project in which an independent, qualified examiner looks at the project’s crash potential and / or safety performance.
Objectives of a road safety audit minimise the risk and severity of road crashes minimise the need for remedial work after construction reduce the whole-of-life costs of the project improve awareness of safe design practices. The essential elements of the process are: ● It is a formal process, not an informal one ● It is conducted by someone who is independent of the designer ● It is conducted by someone with appropriate experience and training ● It is restricted to road safety issues.
Application of Safety Audits Example: for a new road audit may be conducted at: • Feasibility stage • Layout or preliminary design stage • Detailed design stage • Pre-opening stage • In-service stage
9.7 Parking Studies Indicate: • Number and location of parking spaces; • Existing parking practices (duration, etc); • Need to vary time limits or install meters; • Adequacy of existing enforcement methods.
9.7.1 Methods for Parking Studies Select study area. Carry out inventory of defined area. Carry out a cordon count Carry out a parking usage study Survey of all parking spaces at regular intervals
Questionnaires
Typical inventory map
A typical observation sheet
9.7.2 Presentation of Results Tables, graphs and diagrams. Typical results: Variation in demand with time Variations in flow and vehicle accumulation Parking durations Compliance with regulations.
End Module 9, Part 1
