Traffic Operations and Management

The Access-Control Problem on Capacitated FIFO Networks With Unique O-D Paths is Hard

Erera, Alan L.
Daganzo, Carlos F.
Lovell, David J.
2002

This paper is concerned with the performance of multicommodity capacitated networks in a deterministic but time-dependent environment. For a given time-dependent origin-destination table, this paper asks if it is easy to find a way of regulating the input flows into the network to avoid queues from growing internally, i.e., to avoid capacity violations. Problems of this type are conventionally approached in the traffic/transportation field with variational methods such as control theory (if time is continuous) and with mathematical programming (if time is discrete). However, these...

Fingerprinting Traffic From Static Freeway Sensors

Munoz, Juan Carlos
Daganzo, Carlos F.
2002

Ask most commuters and they will agree that congestion has reached an intolerable level. To reduce this congestion, engineers need detailed traffic information. Highly detailed information is also prized by traffic scientists, as a prerequisite to improve current traffic theories. Ideally, engineers and scientists would like to obtain from field data the position of each vehicle on a particular facility at every moment in time. The technology to record space-time vehicle trajectories on a massive scale is in its infancy; therefore, analysts must work with much less data. Many freeways are...

Structure of the Transition Zone Behind Freeway Queues

Munoz, Juan Carlos
Daganzo, Carlos F.
2003

Observations of freeway traffic flow are usually quite scattered about an underlying curve when plotted versus density or occupancy. Although increasing the sampling intervals can reduce the scatter, whenever an experiment encompasses a rush hour with transitions in and out of congestion, some outlying data stubbornly remain beneath the “equilibrium” curve. The existence of these nonequilibrium points is a poorly understood phenomenon that appears to contradict the simple kinematic wave (KW) model of traffic flow. This paper provides a tentative explanation of the phenomenon, based on...

Discretization and Validation of the Continuum Approximation Scheme for Terminal System Design

Ouyang, Yanfeng
Daganzo, Carlos F.
2003

This paper proposes an algorithm that automatically translates the "continuum approximation" (CA) recipes for location problems into discrete designs. It is applied to terminal systems but can also be used for other logistics problems. The study also systematically compares the logistics costs predicted by the CA approach with the actual costs for discrete designs obtained with the automated procedure. Results show that the algorithm systematically finds a practical set of discrete terminal locations with a cost very close to that predicted. The paper also gives conditions under...

A Variable Formulation of Kinematic Waves: Solution Methods

Daganzo, Carlos F.
2003

This paper presents improved solution methods for kinematic wave trafficc problems with concave flow-density relations. As explained in part I of this work, the solution of a kinematic wave problem is a set of continuum least-cost paths in space-time. The least cost to reach a point is the vehicle number. The idea here consists in overlaying a dense but discrete network with appropriate costs in the solution region and then using a shortest-path algorithm to estimate vehicle numbers. With properly designed networks, this procedure is more accurate than existing methods and can be applied...

Neck Brace: System is Needed to Quickly Heal Bottlenecks When Accidents Happen.

Menendez, Monica
Daganzo, Carlos F.
2004

Assessment of the Impact of Incidents near Bottlenecks: Strategies to Reduce Delay

Menendez, Monica
Daganzo, Carlos F.
2004

How the location and duration of an incident affect delays near a recurrent bottleneck is evaluated in this study. With conventional kinematic wave theory and some dimensional analysis, tools are provided to determine whether an incident will cause generalized delays (i.e., delays that have a lingering effect for the whole length of the peak hour) according to the incident's magnitude, location, and duration. The results apply to a broad range of cases, encompassing many types of facilities and incidents. Furthermore, the results can be used as a foundation for developing and implementing...

Logistics Systems Analysis

Daganzo, Carlos F.
2005

This expanded edition of A Logistics Systems Analysis@ includes new - search results and numerous modifications to enhance comprehensiveness and clarity. It has two new sections, a new appendix, and more than half a dozen new figures. A few references have also been added, but the bibli- raphy is not exhaustive. Much of the new material is based on work by Profs. Alan Erera (Georgia Tech), Karen Smilowitz (Northwestern U. ), and by PhD candidate Yanfeng Ouyang (U. C. Berkeley). Their help is gratefully acknowledged. The financial support of the National Science Foundation and the...

Improving City Mobility Through Gridlock Control: An Approach and Some Ideas

Daganzo, Carlos F.
2005

This paper examines the effect of gridlock on urban mobility. It defines gridlock and shows how it can be modeled, monitored and controlled with parsimonious models that do not rely on detailed forecasts. The proposed approach to gridlock management should be most effective when based on real-time observation of relevant spatially aggregated measures of traffic performance. This is discussed in detail. The ideas in this paper suggest numerous avenues for research at the empirical and theoretical levels. An appendix summarizes some of these.

Bus Lanes with Intermittent Priority: Screening Formulae and an Evaluation

Eichler, Michael
Daganzo, Carlos F.
2005

This paper evaluates strategies for operating buses on signal-controlled arterials using special lanes that are made intermittently available to general traffic. The advantage of special bus lanes, intermittent or dedicated, is that they free buses from traffic interference; the disadvantage is that they disrupt traffic. We find that intermittent lanes, unlike dedicated ones, do not significantly reduce street capacity. Intermittence, however, increases the average traffic density at which the demand is served, and as a result increases traffic delay. These delays are more than offset by...