A capacity-increasing mechanism in freeway traffic

A reason is unveiled for the time-varying pattern in discharge flow that is commonly observed at freeway bottlenecks. We hypothesize that four known effects in freeway traffic can interact upstream of a bottleneck in ways that trigger periodic bursts in its discharge flow. Repeated observations of a 3-km freeway stretch support the hypothesis. Controlled experiments show that the capacity-increasing mechanism can be favorably modulated by metering the site’s on-ramps in an unconventional manner. The unconventional strategy repeatedly produced higher average discharge flows and shorter on-ramp queues than did a more traditional metering policy.

► A cause of periodic bursts in freeway bottleneck discharge flow is unveiled.
► The mechanism entails the interactions of four known effects in freeway traffic.
► Metering on-ramps in unconventional ways can favorably influence the mechanism.
► Conventional metering is found to retard the beneficial mechanism.