Traffic Operations and Management

Queue Spillovers in Transportation Networks with a Route Choice

Daganzo, Carlos F.
1998

This paper explores some of the traffic phenomena that arise when drivers have to navigate a network in which queues back up past diverge intersections. If a diverge provides two alternative routes to the same destination and the shorter route has a bottleneck that generates a queue, one would expect that queue to stabilize at an equilibrium level where the travel time on both routes is roughly equal. If the capacity of the alternative route is unlimited then this network can accommodate any demand level. However, if the bottleneck is so close to the upstream end of the link that the...

Remarks on Traffic Flow Modeling and Its Applications

Daganzo, Carlos F.
Brilon, Werner
Huber, Felix
Schreckenberg, Michael
Wallentowitz, Henning
1999

This document presents some recent results and ideas from the University of California (Berkeley) traffic operations group, and at the same time discusses the role of traffic flow modeling in traffic management and control. It stresses the steps that can be taken to reduce congestion and improve traffic efficiency, and how traffic models and theories fit within this picture.

Some Observations of Highway Traffic in Long Queues

Smilowitz, Karen R.
Daganzo, Carlos F.
Cassidy, Michael J.
Bertini, Robert L.
1999

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...

Predictability of Time-Dependent Traffic Backups and Other Reproducible Traits in Experimental Highway Data

Smilowitz, Karen
Daganzo, Carlos F.
1999

Traffic data from a 4-mile long congested rural road in Orinda, California, are used to show that traffic delays and vehicle accumulations between any two generic observers located inside a road section can be predicted from the traffic counts measured at the extremes of the section. The traffic model does not require "recalibration" on the day of the experiment, and works well despite what appears to be location-specific driver behavior.

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 (...

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,...

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.

A Behavioral Theory of Multi-Lane Traffic Flow. Part II: Merges and the Onset of Congestion

Daganzo, Carlos F.
2002

This paper examines the behavior of multi-lane freeway traffic past on-ramps, building on the continuum model of part I and focusing on the onset of congestion. The main complication is that rabbits (fast vehicles) entering from an on-ramp usually stay on the shoulder lane(s) of the freeway for some distance before merging into the fast lane(s). An idealization is proposed, where this distance is taken to be the same for all vehicles. As a result, the system behaves as if there was a fixed buffer zone downstream of the on-ramp where entering rabbits cannot change lanes. The model of part I...

Reproducible Features of Congested Highway Traffic

Smilowitz, K. R.
Daganzo, Carlos F.
2002

Observation of a four-mile long, inhomogeneous, congested traffic stream revealed that vehicle accumulations between detectors vary with flow in a predictable way, and that a macroscopic kinematic wave with a reproducible speed exists in queues despite unusual traffic behavior. As a result, time-dependent vehicle trip times and accumulations inside long queues (and the queue length itself) can be predicted from readily available data without using any “degrees of freedom” to fit the parameters of a model. Experimental vehicle counts were within 20 vehicles of the predictions for over two...