Speed Harmonization with Connected Automated Vehicles
Office of Operations Research and Development
Speed Harmonization with Connected Automated Vehicles Tom Phillips1, Jiaqi Ma1, Daniel J Dailey2, Kelli Raboy1
BACKGROUND & PURPOSE
EXPERIMENTAL PLAN (PHASE 1)
The Federal Highway Administration (FHWA) and Leidos have engaged four university partners, Virginia Tech, California PATH, Mississippi State University, and Texas Transportation Institute, to develop new concepts of Speed Harmonization (SH) and initiate foundational experimental research based upon enabling technologies for automated operation and infrastructure-tovehicle (I2V) communication with connected automation. Two research projects have been funded to explore the effectiveness of SH using field experiments:
Vehicles and Infrastructure The experiment is performed on I-66 using: 1) Three vehicles, equipped with I2V, to control the traffic speed 2) A lead probe vehicle placed in the traffic flow approximately 100 meters ahead of the control vehicles 3) Two probe vehicles approximately 50 meters behind the control vehicles
• Part A: A Freeway Speed Harmonization Experiment Using I2V Communication with Connected, Automated Vehicles (Completed) - 3 exploratory simulation and field studies conducted to obtain insight and prepare for a six-vehicle small experiment • Part B: Automated Speed Harmonization Fundamental Research: Phase 1 (Ongoing) - Conduct comprehensive literature survey for concept development and design detailed experimental plan for large scale field experiments - Implement speed harmonization on an active and congested segment of the I-66 freeway near Washington, DC - Measure the localized effects of SH implementation on traffic stream While many simulation efforts investigating the effectiveness of speed harmonization techniques are done on a large scale, this work is experimental and done on a small scale using macroscopic traffic measures for evaluation and varying the control technology. Previous experimental efforts involving messaging to the drivers (mostly done through variable message signs but also using in-vehicle messaging) involve driver acceptance/compliance. This experiment, the first of its kind, does not require driver compliance, but rather places the control recommendation directly into the longitudinal control loop.
Roadway Layout The illustration on the left demonstrates the roadway layout of the freeway segment during testing. The experiments took place when congestion was just beginning to form on the evaluated freeway segment. The different symbols represent the location of the control and probe vehicles at the time of the experiment.
RESULTS • The control vehicles can be used in automated longitudinal control mode to implement sufficient I2V speed harmonization while operating in traffic. The control vehicles can be expected to operate at the speed recommended (provided that speed is at or below existing traffic speed), with a small time delay. Figures 3 & 4 illustrate the spatial speed trajectories and recommendations below. • Graphical statistics of the leading and following probes (Figures 1 & 2) showed a reduced variability in traffic flow – variability is thus smaller and distributed about a single mode. • Traffic stream statistics showed a significant impact as a result of applying speed harmonization on the probe vehicles. Trajectories on the traffic stream after the speed harmonization reduced oscillatory behavior as characterized using the power spectral densities and measurements (Figure 5 below).
Leading and Following Probability Density Functions The trajectories of the probe and control vehicles are impacted by both the surrounding traffic and speed control enforced by the control vehicles. The control vehicles deviations from the programmed speed profile results primarily from slowing in response to exiting traffic.
Figure 3: Spatial speed trajectories
Figure 4: Control vehicle trajectories and speed recommendations
Figure 1 shows a probability density function (PDF) of a detrended leading probe speed, while Figure 2 shows a PDF of detrended following probe speed.
Figure 5: Power spectral densities of the detrended speed
NEXT STEPS – NEXT PHASE
The figure on the left shows the geographic testing area where the tests and simulations took place. The figure on the right shows the vehicles outfitted with equipment to allow for I2V communication/speed harmonization to take place. Figure 1: PDF of detrended leading probe speed
1Leidos,
Figure 2: PDF of detrended following probe speed
This ongoing work and next phase of the project will document a comprehensive list of state-of-the-art concepts of SH, develop more effective but still practical algorithms as part of a more detailed experimental design, and conduct more advanced field experiments to gain more insight of SH with connected automated vehicles.
Inc., Transportation Solutions and Technology Applications Division; 2Federal Highway Administration, Turner-Fairbank Highway Research Center
Speed Harmonization with Connected Automated Vehicles Tom Phillips1, Jiaqi Ma1, Daniel J Dailey2, Kelli Raboy1
BACKGROUND & PURPOSE
EXPERIMENTAL PLAN (PHASE 1)
The Federal Highway Administration (FHWA) and Leidos have engaged four university partners, Virginia Tech, California PATH, Mississippi State University, and Texas Transportation Institute, to develop new concepts of Speed Harmonization (SH) and initiate foundational experimental research based upon enabling technologies for automated operation and infrastructure-tovehicle (I2V) communication with connected automation. Two research projects have been funded to explore the effectiveness of SH using field experiments:
Vehicles and Infrastructure The experiment is performed on I-66 using: 1) Three vehicles, equipped with I2V, to control the traffic speed 2) A lead probe vehicle placed in the traffic flow approximately 100 meters ahead of the control vehicles 3) Two probe vehicles approximately 50 meters behind the control vehicles
• Part A: A Freeway Speed Harmonization Experiment Using I2V Communication with Connected, Automated Vehicles (Completed) - 3 exploratory simulation and field studies conducted to obtain insight and prepare for a six-vehicle small experiment • Part B: Automated Speed Harmonization Fundamental Research: Phase 1 (Ongoing) - Conduct comprehensive literature survey for concept development and design detailed experimental plan for large scale field experiments - Implement speed harmonization on an active and congested segment of the I-66 freeway near Washington, DC - Measure the localized effects of SH implementation on traffic stream While many simulation efforts investigating the effectiveness of speed harmonization techniques are done on a large scale, this work is experimental and done on a small scale using macroscopic traffic measures for evaluation and varying the control technology. Previous experimental efforts involving messaging to the drivers (mostly done through variable message signs but also using in-vehicle messaging) involve driver acceptance/compliance. This experiment, the first of its kind, does not require driver compliance, but rather places the control recommendation directly into the longitudinal control loop.
Roadway Layout The illustration on the left demonstrates the roadway layout of the freeway segment during testing. The experiments took place when congestion was just beginning to form on the evaluated freeway segment. The different symbols represent the location of the control and probe vehicles at the time of the experiment.
RESULTS • The control vehicles can be used in automated longitudinal control mode to implement sufficient I2V speed harmonization while operating in traffic. The control vehicles can be expected to operate at the speed recommended (provided that speed is at or below existing traffic speed), with a small time delay. Figures 3 & 4 illustrate the spatial speed trajectories and recommendations below. • Graphical statistics of the leading and following probes (Figures 1 & 2) showed a reduced variability in traffic flow – variability is thus smaller and distributed about a single mode. • Traffic stream statistics showed a significant impact as a result of applying speed harmonization on the probe vehicles. Trajectories on the traffic stream after the speed harmonization reduced oscillatory behavior as characterized using the power spectral densities and measurements (Figure 5 below).
Leading and Following Probability Density Functions The trajectories of the probe and control vehicles are impacted by both the surrounding traffic and speed control enforced by the control vehicles. The control vehicles deviations from the programmed speed profile results primarily from slowing in response to exiting traffic.
Figure 3: Spatial speed trajectories
Figure 4: Control vehicle trajectories and speed recommendations
Figure 1 shows a probability density function (PDF) of a detrended leading probe speed, while Figure 2 shows a PDF of detrended following probe speed.
Figure 5: Power spectral densities of the detrended speed
NEXT STEPS – NEXT PHASE
The figure on the left shows the geographic testing area where the tests and simulations took place. The figure on the right shows the vehicles outfitted with equipment to allow for I2V communication/speed harmonization to take place. Figure 1: PDF of detrended leading probe speed
1Leidos,
Figure 2: PDF of detrended following probe speed
This ongoing work and next phase of the project will document a comprehensive list of state-of-the-art concepts of SH, develop more effective but still practical algorithms as part of a more detailed experimental design, and conduct more advanced field experiments to gain more insight of SH with connected automated vehicles.
Inc., Transportation Solutions and Technology Applications Division; 2Federal Highway Administration, Turner-Fairbank Highway Research Center
