Simulation Models Suggest that Cooperative Lane Change Maneuvers Among Connected Autonomous Vehicles Can Decrease Vehicle Stops by 89 Percent, Improve Travel Time by 22 Percent, and Reduce Fuel Consumption by Seven Percent.
A Simulation Analysis Assessed the Potential Impact of Using Cooperative Lane Change Algorithms on California Highway I-710.
Made Public Date


United States

Connected Autonomous Vehicles: Safety During Merging and Lane Change and Impact on Traffic Flow

Summary Information

The objective of the study is to address the problem of cooperative lane change maneuvers where vehicles communicate with each other and negotiate the creation of safe spacings in order to merge without taking any safety risks. The study also includes platoons of vehicles, by developing the communication protocol to be followed with three lane changing strategies (Synchronous, Leader First and Last Vehicle First), which affects the gap generation and lane changing behavior for the vehicles. Measurement verification steps were developed to identify sensor or communication failures. Extensive simulations are used to demonstrate and evaluate the approach and assess the traffic and environmental impact under different traffic conditions.


The proposed approach in this study requires that the merging vehicle negotiates the creation of a safety gap in the destination lane. Until the lane change maneuver is completed, the merging vehicle operates as following two possible vehicles, one in its own lane and one in the destination lane. In addition, the vehicle behind the merge in the destination lane operates as if the merging vehicle had already changed lanes. The proposed methods were evaluated using vehicle level simulations with detailed control of a small set of vehicles and microsimulation for large scale scenarios. The microsimulation experiments take place on a 16-km long southbound stretch of the I-710 California highway. The chosen demands were 6000 veh/h and 6500 veh/h with 15 percent of platoons. In order to evaluate the effects of the lane change controller algorithm in the simulation, lane-based analyses were also performed. 


  • The vehicle-level simulation revealed that the Leader First strategy (vehicles move in one at a time while the gap in the adjacent lane is being generated) for platoon lane changing showed an improvement of at least 20 percent in terms of reserved space-time (that expresses road sub-utilization during the maneuver) for all relative speeds.
  • The optimum lane change trajectory for moving into a slower lane is given by the Leader First strategy.
  • The Last Vehicle First strategy (the last vehicle is the first to change lanes, then it creates the proper spacing for the others) yields better acceleration costs but has the longest maneuver duration.
  • With control over gap generation and lane changing maneuvers, the traffic flow gets smoother since vehicles can perform lane changes before being forced to a full stop. This decreases the number of stops (up to 88.75 percent) and the total travel time (up to 22.13 percent). Consequentially, fuel consumption and CO2 emission rates are also lowered by seven to eight percent, respectively.
  • The gains in traffic flow efficiency as evaluated by the lane-based analysis show improved traffic flow in the simulations with lane change control; the maximum capacity was achieved with control despite incidents while the maximum flow is reduced by 14 percent in the case without control.
Results Type