Driver turn-taking behavior in congested freeway merges

Data from four merge locations in northern California and Toronto, Ontario, Canada, unveil a notable feature of driver turn taking. It was observed that queued vehicles from the on-ramp and freeway traffic streams entered a congested merge in some (nearly) fixed ratio that was independent of the merge outflow. Drivers in competing traffic streams thus entered the merge by adopting some definite turn-taking behavior, and this behavior was not influenced by the severity of the exogenous flow restriction from downstream. The findings validate part of an existing theory of merging traffic and should be considered when any new such theories are developed.