Traffic Operations and Management

Identifying the Onset of Congestion Rapidly with Existing Traffic Detectors

Coifman, Benjamin
1999

From an operations standpoint, the most important task of a traffic surveillance system is determining reliably whether the facility is free flowing or congested. The second most important task is responding rapidly when the facility becomes congested. Other tasks, such as quantifying the magnitude of congestion, are desirable, but tertiary. To address the first two tasks, this paper presents a new approach for traffic surveillance using existing detectors. Rather than expending a considerable effort to detect congested conditions, the research employs a relatively simple strategy to look...

The Cell Transmission Model: Network Traffic

Daganzo, Carlos
1994

This paper shows how the evolution of multicommodity traffic flows over complex networks can be predicted over time, based on a simple macroscopic computer representation of traffic flow that is consistent with the kinematic wave theory under all traffic conditions. After a brief review of the basic model for one link, the paper describes how three-legged junctions can be modeled. It then introduces a numerical procedure for networks, assuming that a time-varying origin-destination table is given and that the proportion of turns at every junction is known. These assumptions are reasonable...

Travinfor Evaluation: Value Added Reseller (var) Study Phase 1 Results

Loukakos, D.
Hall, R.
Weissenberger, S.
Yim, Y. B.
1996

TravInfo is a Field Operational Test (FOT) in advanced traveler information systems (ATIS) for the San Francisco Bay Area sponsored by the Federal Highway Administration (FHWA). The project involves a public/private partnership which seeks to compile, integrate and broadly disseminate timely and accurate multi-modal traveler information through commercial products and services. This working paper is part of the Technology Element of the TravInfo evaluation. It presents the results of the "before" wave of the Value-Added-Reseller (VAR) study, in which 17 TravInfo registered VARs and 16 non-...

On-line Traffic Signal Control Scheme with Real-time Delay Estimation Technology

Liu, Henry X.
Oh, Jun S.
Oh, Seri
Chu, Liany
Recker, Will
2001

This paper presents an on-line signal control scheme integrated with the real-time intersection delay estimation technology. The primary goal of this study is to design a complementary optimization module to the existing controller to minimize the total delay experienced by traffic and improve the system performance at the signalized intersections. This paper proposes a feedback control algorithm that optimizes the signal timing plan based on delay estimated via vehicle re-identification technology. Main thrust of the algorithm is on-line control capability utilizing direct delay measures...

Using Vehicles Equipped with Toll Tags as Probes for Providing Travel Times

John, Wright
Dahlgren, Joy
2001

The introduction of electronic toll collection on the eight bridges crossing San Francisco Bay has provided the means for a relatively simple and low cost system for measuring travel times on many Bay Area bridges and roads. The toll tags sued for electronic toll collection can be read by readers at various locations on congested roads. The time of reading is recorded so that the time difference between when a vehicle passes one reader and passes the next can be computed. Such a system is already operating in Houston, where it is the primary source of travel time data. Capital costs per...

Methodologies For Assessing The Impacts Of Highway Capacity Enhancements On Travel Behavior

Liu, Heng
Hall, Randolph
1998

Acceptance of ITS components that are designed to increase capacity will hinge on the extent to which additional capacity induces additional travel. This study addressed methodologies for studying the effects of capacity on travel: 1) before and after studies or travel times and volumes in corridors in which capacity had been increased, 2) surveys of users of routes on which capacity had been increased, and 3) statistical changes in county VMT as a function of freeway capacity. On I-80 in the Bay Area, the site selected for the investigation, travel times and volumes were quite variable....

Orange County Transit Probe Evaluation: Phase I Institutional Findings

Hall, Randolph W.
1997

This report documents the institutional issues that have faced the Orange County probe project, a multi-agency project designed to equip a fleet of buses with Global Positioning System (GPS) based tracking equipment and to use tracking data for multiple purposes. The usefulness of the data involve: 1) bus schedule adherence and fleet management; 2) collection of information on roadway traffic congestion; and, 3) dissemination of transit data to patrons.

Evaluation Framework For Commercial Vehicle Responses To Congestion Pricing

Wachs, Martin
Kawamura, Kazuya
1997

This report presents a short-run framework for analyzing the impacts of congestion pricing on commercial vehicles. The framework is based on microeconomics principles and past theoretical studies of congestion pricing. The relationship between value of time and the welfare gain/loss induced by using congestion pricing is identified. The social cost function and empirical demand and supply functions are also discussed.

Travel Time Estimation on the San Francisco Bay Area Network Using Cellular Phones as Probes

Ygnace, Jean-Luc
Drane, Chris
Yim, Y. B.
de Lacvivier, Renaud
2000

Current traffic travel time estimates are largely based on road sensors embedded in the pavement. Today technical developments in cellular positioning and the spread of wireless phones provide the opportunity to track cell phone equipped drivers as traffic probes. The Federal Communication Commission Phase II mandate for Enhanced-911 (E-911) requires that wireless carriers must provide the location of a 911 wireless call by October 1, 2001 to the Public Safety Answering Point (PSAP), within approximately 125 meters, or under one-tenth of a mile in the majority of situations. The motivation...

Effect of Longitudinal Control on Capacity

Beji, Yousser
1987

This paper focuses on what benefits a longitudinal control system can be expected to render to the present highway system.There are three major reasons why longitudinal control should be expected to improve traffic flow and to reduce accidents.(1) It may permit higher traffic densities with uniform spacing forming an even distribution with increased travel speeds and consequently higher capacity.(2) It may reduce the rate of rear-end collisions that occur on urban freeways.(3) It can provide increased stability in traffic flow (shockwaves due to human response characteristics are the main...