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hubie writes:

It is no surprise that driver lane changes in traffic affects the flow of traffic itself. When the density of vehicles is low, it can lead to efficiencies in traffic flow. However, when the density reaches a certain level, it has the opposite effect. In this situation, when a driver moves into another lane, the vehicle behind the lane-changing vehicle suffers a delay, which leads to a delay imposed upon the vehicle behind it, etc., that compounds itself as a delay that ripples through the traffic behind. There are several traffic flow models that simulate this, but they can be contradictory in their results. A group of researchers from the Department of Traffic Management School at the People's Public Security University of China obtained quantitative data on this effect by flying DJI Phantom 4 drones over a target vehicle driving in congested traffic. They found that a single lane change (LC) adds between 3.9–9.5 seconds of delay to the cars in the trarget lane.

A key dependency observed, which would not surprise too many people who are accustomed to driving in congested traffic, was the space between vehicles. They found that 5.5 meters was a break point between behavior for the trailing vehicle in the next lane. It was found that when the distance between vehicles is less than 5.5 m, the vehicle following the target vehicle tends to drive at a constant speed or decelerate, but when the distance between vehicles is greater than 5.5 m, the vehicle following the target vehicle tends to first accelerate to prevent the target vehicle from entering the lane (Ed note: I've always thought of this as "Philadelphia driving etiquette"), but then the speed gradually decreases when the target vehicle is forcibly inserted.

This research provides a theoretical reference for the analysis of LC of driverless vehicles. To successfully complete a lane change, a driverless vehicle must comprehensively consider the running state of the vehicle following it, not only to improve its own running speed, but also to reduce the impact on the vehicle behind it.

Journal Reference:
Yang, Q., Lu, F., Ma, J. et al. Analyzing the delays of target lane vehicles caused by vehicle lane-changing operation. Sci Rep 11, 22047 (2021).
DOI: 10.1038/s41598-021-00262-1

Original Submission