ITS Berkeley

Possible Explanations of Phase Transitions in Highway Traffic

Daganzo, C. F.
Cassidy, M. J.
Bertini, R. L.
1999

It is shown that all the phase transitions in and out of freely flowing traffic reported earlier for a German site could be caused by bottlenecks, as are all the transitions observed at two other sites examined here. The evidence suggests that bottlenecks cause these transitions in a predictable way, and does not suggest that stoppages (jams) appear spontaneously in free flow traffic for no apparent reason. It is also shown that many of the complicated instability phenomena observed at all locations can be explained qualitatively in terms of a simple Markovian theory specific to traffic...

A Behavioral Theory of Multi-Lane Traffic Flow Part I: Long Homogeneous Freeway Sections

Daganzo, Carlos F.
1999

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...

Experimental Results With Moving Bottlenecks

Munoz, Juan Carlos
Daganzo, Carlos F.
2000

In this paper, the author present field observations and a new theory regarding moving bottlenecks on freeways. The observations focus on the occurrence of a steadily moving bottleneck on the I-880 freeway in Oakland, California, which was identified and characterized from loop detector data, including the behavior of the traffic stream around it. Oblique plots were used to reveal the location in time and space of the moving bottleneck's appearance including its trajectory over the freeway section. A set of controlled floating-vehicle experiments are described which involved the...

Access Control on Networks with Unique Origin–Destination Paths

Lovell, David J.
Daganzo, Carlos F.
2000

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 (...

A Pareto Improving Strategy for the Time-Dependent Morning Commute Problem

Daganzo, Carlos F.
Garcia, Reinaldo C.
2000

This research shows that certain time-dependent congestion reduction schemes involving tolls have the potential for benefiting every driver even if the collected revenues are not returned to the payers. The paper considers a population of commuters who use a single bottleneck during the morning rush hour and try to arrive at work on time. It is assumed that the number of commuters is fixed (independent of the control strategy) and that each commuter wishes to pass through the bottleneck at a given time, which may differ across commuters. Commuters are otherwise identical. Each of them...

Experimental Characterization of Multi-Lane Freeway Traffic Upstream of an Off-Ramp Bottleneck

Munoz, Juan Carlos
Daganzo, Carlos F.
2000

This report describes field observations of multi-lane freeway traffic upstream of an oversaturated off-ramp. It is based on empirical evidence from freeway I-880 (northbound) near Oakland, California. The report presents two diagnostic tools that reveal hidden features of the traffic stream and, based on these findings, proposes congestion mitigation strategies that could work for similar locations with little or no construction.

Taking Turns: Rx for Congestion

Daganzo, Carlos F.
2000

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,...

Asymptotic Approximations for the Transportation LP and Other Scalable Network Problems

Daganzo, Carlos F.
Smilowitz, Karen R.
2000

Network optimization problems with a "scalable" structure are examined in this report. Scalable networks are embedded in a normed space and must belong to a closed family under certain transformations of size (number of nodes) and scale (dimension of the norm). The transportation problem of linear programming (TLP) with randomly distributed points and random demands, the earthwork minimization problem of highway design, and the distribution of currents in an electric grid are examples of scalable network problems. Asymptotic formulas for the optimum cost are developed for the case where...

Ten Strategies for Freeway Congestion Mitigation with Advanced Technologies

Daganzo, Carlos F.
Laval, Jorge
Munoz, Juan Carlos
2002

This report presents ten strategies for improving freeway performance that have become feasible with the advent of new software and hardware technologies for traffic control. Most of the strategies can be applied with advanced implementations of existing hardware. The strategies have in common that they can be rigorously tested. heir measures of performance can be reliably obtained and do not depend on the accuracy of data- hungry, large-scale models.