Automated vehicle (AV) technology is progressing and governments are beginning to open public roads to test AVs. It is broadly expected that diffusion of AVs within the vehicle fleet will yield a positive impact on capacity of transportation infrastructure. This paper considers the ex-ante impacts of partially, highly, and connected highly AVs on freeway capacity in Germany.
To estimate the impacts of an unknown number of AVs on current infrastructure, penetration of AVs within the German vehicle stock was predicted for the next several decades and considered within the capacity analysis. This was done by examining the impacts of AVs on individual types of basic, merge, diverge, and weaving segments of the freeway network with respect to the predicted penetration rates. Therefore, a microscopic traffic flow simulation was deployed to model the altered driving behavior of AVs on the segments typically represented in the German freeway network. Finally, the local impacts were extrapolated and assigned to the country-wide traffic flow model of Germany (PTV Validate) to draw economic conclusions.
Simulation results clearly convey that the impact of vehicle automation on capacity depends strongly on the driving behavior of automated vehicles (AVs), especially the longitudinal behavior, as well as their penetration rate within the vehicle fleet.
Initial introduction of AVs that drive conservatively yields a minor reduction in capacity (a peak reduction of almost 10 percent by 2050) of freeways until 2050, when penetration of the first generation of more conservative AVs begins to shrink in lieu of growth in the penetration of connected AVs. As penetration of connected AVs increases, capacity increases by 30 percent by 2070.
Capacity deteriorates due to a gradual increase in penetration rates of partially automated vehicles (PAVs) and highly automated vehicles (HAVs), whose behavior is conservative compared to conventional vehicles, regardless of the road geometry.
Despite 26 percent of vehicles being connected AVs in 2050, their positive impact on the capacity is negligible, confirming that the benefits of connected AVs are not significant in low penetration rates. The capacity benefit is realized to a greater extent when automated technology is combined with connected technologies and when extremely short headways are allowed as in scenario 2050+ upper bound.
Automation of vehicles could increase capacity by 45 percent in basic road segments. However, intensive lane changing has a major impact on capacity and cooperation between vehicles is critical, thus intensive lane changing areas are negatively impacted by conservative PAVs and HAVs. Connected AVs keep very short headways insufficient for lane changes, so even under the most ideal scenarios capacity improvement in these areas is limited.
(Our website has many links to other organizations. While we offer these electronic linkages for your convenience in accessing transportation-related information, please be aware that when you exit our website, the privacy and accessibility policies stated on our website may not be the same as that on other websites.)