Autonomous vehicles (AVs) represent a potentially disruptive yet beneficial change to our transportation system. This new technology has the potential to impact vehicle safety, congestion, and travel behavior. All told, major social AV impacts in the form of crash savings, travel time reduction, fuel efficiency and parking benefits are estimated to approach $2000 to per year per AV, and may eventually approach nearly $4000 when comprehensive crash costs are accounted for. Yet barriers to implementation and mass-market penetration remain. Initial costs will likely be unaffordable. Licensing and testing standards in the U.S. are being developed at the state level, rather than nationally, which may lead to inconsistencies across states. Liability details remain undefined, security concerns linger, and without new privacy standards, a default lack of privacy for personal travel may become the norm. The impacts and interactions with other components of the transportation system, as well as implementation details, remain uncertain. To address these concerns, the federal government should expand research in these areas and create a nationally recognized licensing framework for AVs, determining appropriate standards for liability, security, and data privacy.

https://www.aamva.org/WorkArea/DownloadAsset.aspx?id=6738

Preparing a nation for autonomous vehicles: opportunities, barriers and policy recommendations

Autonomous vehicles (AVs) represent a potentially disruptive yet beneficial change to the transportation system This new technology has the potential to impact vehicle safety, congestion, and travel behavior All told, major social AV impacts in the form of crash savings, travel time reduction, fuel efficiency and parking benefits are estimated to approach $2,000 to per year per AV, and may eventually approach nearly $4,000 when comprehensive crash costs are accounted for Yet barriers to implementation and mass-market penetration remain Initial costs will likely be unaffordable Licensing and testing standards in the US are being developed at the state level, rather than nationally, which may lead to inconsistencies across states Liability details remain undefined, security concerns linger, and without new privacy standards, a default lack of privacy for personal travel may become the norm The impacts and interactions with other components of the transportation system, as well as implementation details, remain uncertain To address these concerns, the federal government should expand research in these areas and create a nationally recognized licensing framework for AVs, determining appropriate standards for liability, security, and data privacy

Preparing a Nation for Autonomous Vehicles: Opportunities, Barriers and Policy Recommendations

Intelligent vehicle cooperation based on reliable communication systems contributes not only to reducing traffic accidents but also to improving traffic flow. Adaptive cruise control (ACC) systems can gain enhanced performance by adding vehicle-vehicle wireless communication to provide additional information to augment range sensor data, leading to cooperative ACC (CACC). This paper presents the design, development, implementation, and testing of a CACC system. It consists of two controllers, one to manage the approaching maneuver to the leading vehicle and the other to regulate car-following once the vehicle joins the platoon. The system has been implemented on four production Infiniti M56s vehicles, and this paper details the results of experiments to validate the performance of the controller and its improvements with respect to the commercially available ACC system.

/pdf/cooperative-adaptive-cruise-control-in-real-traffic-35mggeon75.pdf

Cooperative Adaptive Cruise Control in Real Traffic Situations

Experts predict that new automobiles will be capable of driving themselves under limited conditions within 5–10 years, and under most conditions within 10–20 years. Automation may affect road vehicle energy consumption and greenhouse gas (GHG) emissions in a host of ways, positive and negative, by causing changes in travel demand, vehicle design, vehicle operating profiles, and choices of fuels. In this paper, we identify specific mechanisms through which automation may affect travel and energy demand and resulting GHG emissions and bring them together using a coherent energy decomposition framework. We review the literature for estimates of the energy impacts of each mechanism and, where the literature is lacking, develop our own estimates using engineering and economic analysis. We consider how widely applicable each mechanism is, and quantify the potential impact of each mechanism on a common basis: the percentage change it is expected to cause in total GHG emissions from light-duty or heavy-duty vehicles in the U.S. Our primary focus is travel related energy consumption and emissions, since potential lifecycle impacts are generally smaller in magnitude. We explore the net effects of automation on emissions through several illustrative scenarios, finding that automation might plausibly reduce road transport GHG emissions and energy use by nearly half – or nearly double them – depending on which effects come to dominate. We also find that many potential energy-reduction benefits may be realized through partial automation, while the major energy/emission downside risks appear more likely at full automation. We close by presenting some implications for policymakers and identifying priority areas for further research.

/pdf/help-or-hindrance-the-travel-energy-and-carbon-impacts-of-4552l0f6o0.pdf

Help or hindrance? The travel, energy and carbon impacts of highly automated vehicles

Vehicle longitudinal control systems such as (commercially available) autonomous Adaptive Cruise Control (ACC) and its more sophisticated variant Cooperative ACC (CACC) could potentially have significant impacts on traffic flow. Accurate models of the dynamic responses of both of these systems are needed to produce realistic predictions of their effects on highway capacity and traffic flow dynamics. This paper describes the development of models of both ACC and CACC control systems that are based on real experimental data. To this end, four production vehicles were equipped with a commercial ACC system and a newly developed CACC controller. The Intelligent Driver Model (IDM) that has been widely used for ACC car-following modeling was also implemented on the production vehicles. These controllers were tested in different traffic situations in order to measure the actual responses of the vehicles. Test results indicate that: (1) the IDM controller when implemented in our experimental test vehicles does not perceptibly follow the speed changes of the preceding vehicle; (2) strings of consecutive ACC vehicles are unstable, amplifying the speed variations of preceding vehicles; and (3) strings of consecutive CACC vehicles overcome these limitations, providing smooth and stable car following responses. Simple but accurate models of the ACC and CACC vehicle following dynamics were derived from the actual measured responses of the vehicles and applied to simulations of some simple multi-vehicle car following scenarios.

https://hal.archives-ouvertes.fr/hal-01091160/document

Modeling cooperative and autonomous adaptive cruise control dynamic responses using experimental data

This study used microscopic simulation to estimate the effect on highway capacity of varying market penetrations of vehicles with adaptive cruise control (ACC) and cooperative adaptive cruise control (CACC). Because the simulation used the distribution of time gap settings that drivers from the general public used in a real field experiment, this study was the first on the effects of ACC and CACC on traffic to be based on real data on driver usage of these types of controls. The results showed that the use of ACC was unlikely to change lane capacity significantly. However, CACC was able to increase capacity greatly after its market penetration reached moderate to high percentages. The capacity increase could be accelerated by equipping non-ACC vehicles with vehicle awareness devices so that they could serve as the lead vehicles for CACC vehicles.

Impacts of cooperative adaptive cruise control on freeway traffic flow

Freeway corridor traffic flow is limited by bottleneck flow. If the section upstream of a bottleneck is congested, the bottleneck flow will drop well below its capacity. A logical approach to maximizing recurrent bottleneck flow is to create a discharge section immediately upstream of the bottleneck. This paper proposes a control strategy for combining variable speed limits (VSL) and coordinated ramp metering (CRM) design to achieve this objective when the bottleneck can be represented as a lane (or virtual lane) reduction. At each time step, VSL is designed first, with mainline flow, on-ramp demand and length, and driver acceptance taken into account. VSL values are determined for three locations: (a) the critical VSL to regulate the discharge section flow to match bottleneck capacity, (b) the VSL for the potentially congested section (mainline storage), and (c) the VSL upstream of the congestion tail. With the selected VSL, the first-order mainline flow model is linearized and then used for CRM design with model predictive control to minimize the difference between scaled total travel time (or vehicle hours traveled) and the total travel distance (equivalent to vehicle miles traveled). Microscopic simulation shows that this control strategy should improve bottleneck throughput significantly.

Novel Freeway Traffic Control with Variable Speed Limit and Coordinated Ramp Metering

Freeway corridor traffic flow is limited by bottleneck flow. A possible approach for maximizing recurrent bottleneck flow is to create a discharge section immediately upstream of the bottleneck. This paper proposes a control strategy for combining Variable Speed Limits (VSL) and Coordinated Ramp Metering (CRM) design to achieve this objective when the bottleneck can be modeled as a lane drop (or virtual lane drop) and/or weaving section. The control design strategy is to design VSL first and then use Finite Time Horizon Model Predictive Control to design Coordinated Ramp Metering. Microscopic simulation results showed that the control strategy could improve traffic throughput significantly.

A new approach for combined freeway Variable Speed Limits and Coordinated Ramp Metering

The development of two mobility applications using DSRC wireless communications among vehicles and between vehicles and the roadway infrastructure to improve mobility on limited-access highways is described. The first application combines ramp metering with variable speed limits to enhance control of traffic so that traffic flow breakdowns can be deferred or avoided at bottleneck locations. The second application uses vehicle-vehicle communication to improve the performance of adaptive cruise control systems so that they can operate safely with smaller longitudinal gaps and vehicle-roadside communication to provide adjustments to their set speed and gap settings to adapt to changes in local traffic conditions.

Development and Evaluation of Selected Mobility Applications for VII

The operations of freeway ramp metering and urban traffic network signal control are independent in most areas. Such situation may cause some conflict between traffic streams of the two subsystems, or, at least, their dynamic interactions have not been taken into account from an overall system viewpoint. Traffic performance can be improved if the controls of these two subnetworks are integrated. This paper proposes a novel signal control strategy for the feeding intersection and a coordination strategy for integrating it with the corresponding freeway onramp metering. UP ALINEA with queue-overwrite is used for the ramp metering. A signal optimization, which takes into account the available ramp space and traffic demand, is developed for intersection signal control. A calibrated micro-simulation is used to compare the proposed control/coordination strategies and current control plans in the field. Simulation result shows that, even though the overall system performance only gets a marginal improvement, intersection delay reduces significantly.

Dongyan Su

Papers

Impacts of cooperative adaptive cruise control on freeway traffic flow

Novel Freeway Traffic Control with Variable Speed Limit and Coordinated Ramp Metering

A new approach for combined freeway Variable Speed Limits and Coordinated Ramp Metering

Development and Evaluation of Selected Mobility Applications for VII

Coordinated Ramp Metering and Intersection Signal Control