Roads/Highways

The arrival times of vehicles traveling southbound along a two-lane, bidirectional highway were recorded at eight neighboring locations upstream of a bottleneck caused by an oversaturated traffic signal. Cumulative curves constructed from these observations describe completely and in great detail the evolution of the resulting long queues. These queues formed directly upstream of the signal when the signal’s service rate fell below the southbound arrival rates, and never formed away from the bottleneck. The predictability of bottlenecks like the one studied here can be exploited to manage...

This paper proposes a macroscopic behavioral theory of traffic dynamics for homogeneous, multi-lane freeways. The theory makes predictions for separate groups of lanes while recognizing that the traffic stream is usually composed of aggressive and timid drivers. Its principles are so simple that non-scientist drivers can understand them. The simplest version of the theory, which is described in its full complexity without calculus, is shown to be qualitatively consistent with experimental observations, including the most puzzling. Its predictions agree with the following phenomena: (i) the...

This paper presents improved time-dependent control strategies for small freeway networks with bottlenecks and unique origin–destination paths. It is assumed that there are no spill-overs from any of the freeway exits so that freeway queues and delays can be completely avoided by regulating access to the system so as to maintain bottleneck flows strictly below capacity. It is also assumed that the time-dependent origin–destination table and the time-dependent bottleneck capacities are known, although not always a priori. The proposed control strategies attempt to minimize the total delay (...

Freeway congestion at bottlenecks is different from tie-ups caused by accidents and other random incidents. It’s recurrent and therefore more easily diagnosed and perhaps even more easily controlled. Thus, at least in principle, we can reduce bottleneck congestion by modifying either the freeway’s design or the management policies that affect freeway operations. Unfortunately, the most obvious modifications often redistribute benefits and burdens unevenly, so some people feel they’d be worse off because of the so- c a l l e d improvements. The resulting clamor often leads to inaction,...