UK Simulation Study Found 53 to 58 Percent Traffic Conflict Reduction with a Dedicated Lane for Connected and Automated Vehicles at 80 Percent Market Penetration Rate.
Manchester Study Evaluated Safety Impacts of Dedicated Lanes for CAVs With Calibrated and Validated Simulation.
Manchester, United Kingdom
Network-wide safety impacts of dedicated lanes for connected and autonomous vehicles
Summary Information
Cooperative, Connected, and Automated Mobility (CCAM), powered by Connected and Automated Vehicles (CAV), has the potential to transform future transportation systems, by enhancing traffic flow, shortening travel time, reducing delays, and providing safety benefits over traditional vehicles. This study evaluated the safety impacts of using a dedicated lane for CAVs on urban highways and arterials using a five-square-mile traffic simulation in Manchester, UK. The study used traffic data for the evening peak hour to estimate the traffic flow for passenger vehicles, large goods vehicles (LGVs), and heavy goods vehicles (HGV).
METHODOLOGY
Simulation analyses evaluated the impact of dedicated CAV lane placement under various scenarios, including no dedicated lane and placement on the innermost or outermost lanes of motorways and major arterials. The study modeled 1st and 2nd generation level 5 CAVs, as well as human-driven vehicles (HDVs), in eight market penetration rate (MPR) combinations in 20 percent increments. Passenger vehicles were modeled only as CAVs, while LGVs and HGVs were tested as both HDVs and CAVs. The study assessed traffic conflicts using thresholds for time-to-collision (TTC) and post-encroachment time (PET), with lower values indicating higher crash severity. Events with TTC or PET equal to zero were classified as potential crashes. Conflicts were defined as events with TTC between 0 and 1.5s (varying by vehicle type) and PET between 0 and 5s.
FINDINGS
- At 80 percent CAV MPR (evenly split between 1st and 2nd gen), traffic conflicts reduced between 53 and 58 percent for all dedicated lane placement scenarios.
- With a dedicated CAV lane, the combination of 40 percent HDVs, 40 percent 1st Gen CAVs, and 20 percent 2nd Gen CAVs MPR mix led to the most overall safety benefits, with an up to 12 percent reduction in crashes per vehicle-kilometer travelled compared to the no dedicated lane scenario.
- The MPR combination (40-40-20 of HDVs, 1st gen CAVs, and 2nd gen CAVs) also led to up to 12 and 2.4 percent decrease in delays and travel time, respectively.
- Dedicated lanes are not beneficial at low CAV MPRs (around 20 percent).
