South Korean Microsimulation Study Reveals Mobility and Efficiency Benefits Associated with Increased Automated Vehicle Penetration Levels.
Nationwide, South Korea
The Impact of Automated Vehicles on Traffic Flow and Road Capacity on Urban Road Networks
Summary Information
Automated Vehicles (AVs) have great potential to improve traffic capacity and efficiency of transport systems. This study investigated the impact of gradual increments of AV penetration and traffic volume on delays and capacity on urban roads, by using microsimulation and considering parameters for AVs set at the Society of Automotive Engineers (SAE) level 4 of automation, involving cars that do not require human intervention in most circumstances. A real road network from South Korea, including 13 intersections and 4.5 km of roads with varying lane numbers from one to five in one direction, was used for the microsimulation. A total of 36 scenarios were assessed through a combination of AV penetrations and increased traffic volumes, based on data collected in July 2020.
METHODOLOGY
The researchers recorded traffic flows using video cameras for two hours from 7 AM to 9 AM at each intersection of the network as well as traffic volume, queue lengths, traffic signal information on three weekdays in July 2020 to reflect the traffic conditions found in a real road network in Seongnam, South Korea. Traffic counts were used for modeling, calibration and validation of Human Driven Vehicles (HDVs), whereas the traffic signal data were used to verify the traffic signal data provided by the Seongnam city council. A total of 36 scenarios were developed and run for analysis by a combination of six AV penetration rates and six traffic volume increments. The base scenario considered a traffic environment with no AVs and no traffic volume increase. All scenarios of microsimulation were run ten times with different seed numbers to improve accuracy of the outputs. Four network performance indicators: average travel time, average vehicle speed, average delay, and stop frequency at intersections, were used to assess the impact of AVs and the increase in traffic volumes on urban roads.
FINDINGS
- This study found that, with an increase in AV penetration from zero to 100 percent, the average delay decreased from 126.65 s to 87.74 s (a 31 percent reduction) and the average travel time was reduced from 229.99 s to 189.75 s (a 17 percent reduction).
- The average vehicle speed increased by 21 percent (from 22.08 km/h to 26.71 km/h), as the AV penetration rates went from zero to 100 percent.
- Regarding stop frequency at intersections, the study revealed that vehicles made 2.67 stops on average for zero percent AV penetration and 2.1 stops for the 100 percent penetration level, corresponding to a 21 percent reduction in stop frequency. As the penetration rate increased, stop frequency decreased for both AVs and HDVs, with a slightly lower frequency of stops for HDVs compared to AVs.
- In terms of road capacity increase, when the penetration of AVs was saturated at 100 percent, the road network could accommodate 40 percent more traffic.
