Roads/Highways

Assessment of the Applicability of Cooperative Vehicle-Highway Automation Systems to Bus Transit and Intermodal Freight: Case Study Feasibility Analyses in the Metropolitan Chicago Region

Shladover, Steven E.
Miller, Mark A.
Yin, Yafeng
Balvanyos, Tunde
Bernheim, Lauren
Fishman, Stefanie R.
Amirouche, Farid
Mahmudi, Khurran T.
Gonzalez-Mohino, Pedro
Solomon, Joseph
Rawling, Gerald
Iris, Ariel
Bozic, Claire
2004

This report presents the results of its performance assessment of the feasibility of applying cooperative vehicle-highway automation systems (CVHAS) to bus transit and freight movements in the metropolitan Chicago area. Cooperative vehicle-highway automation systems are systems that provide driving control assistance or fully automated driving and are based on information about the vehicle's driving environment that can be received by communication from other vehicles or from the infrastructure, as well as from their own on-board sensors.

Health of California’s Loop Detector System

Rajagopal, Ram
Varaiya, Pravin
2007

The California Department of Transportation (Caltrans) freeway sensor network has two components: the sensor system of 25,000 inductive loop sensors grouped into 8,000 vehicle detector stations (VDS) and covering 30,500 freeway direction-miles; and the communication network over which the sensor measurements are transported to Caltrans Traffic Management Centers. The sensor network is virtually the only source of data for use in traffic operations, performance measurement, planning and traveler information. However, the value of these data is greatly reduced by the poor reliability of the...

Freeway On-Ramp Metering, Delay Savings, and Diverge Bottleneck

Cassidy, Michael J.
2003

An effort was made to clarify certain issues concerning freeway onramp metering and its potential for saving commuter delay. Simple analogies were used to show that delay is reduced if ramp metering increases the rates at which commuters exit the freeway. Contrary to what is frequently reported in the literature, higher travel speeds and flows on links within a freeway system are not evidence of diminished delay and this too was made clear by the analogies. The discussion explains why a metering scheme should be specially tailored to the freeway it serves, and why no single metering logic...

Validation of Daganzo's Behavioral Theory of Multi-Lane Traffic Flow: Final Report

Banks, James H.
Amin, Mohammad R.
Cassidy, Michael J.
Chung, Koohong
2003

A study was conducted to verify C. F. Daganzo's behavioral theory of multi-lane traffic flow (1, 2). This study was conducted by teams from San Diego State University and the University of California at Berkeley who worked independently on a series of case studies to test predictions derived from the theory. The results of the study suggest that some of the phenomena predicted by Daganzo do occur, but not at all locations, and that the underlying behavioral assumptions are oversimplified. Specifically, the types of flow- density (or flow-occupancy) relationship assumed by Daganzo were...

Stationary Models of Unqueued Freeway Traffic and Some Effects of Freeway Geometry

Cassidy, Michael J.
Anani, Shadi B.
2003

Occupancies and flows were jointly sampled from numerous freeway segments in nearly stationary, unqueued traffic. The data from one segment were typically averaged across all lanes there and plotted. Each plot was compared with one sampled at a neighboring freeway segment, with the two segments differing only in their number of travel lanes. Such comparisons were repeated for a total of five pairs of segments on five freeways in and near Toronto, Canada and in California. All occupancy-flow relations were piece-wise linear in form for average flows up to about 2,000 vehicles per hour per...

Test of Theory of Driver Behavior on Homogeneous Freeways

Chung, Koohong
Cassidy, Michael J.
2004

A theory that can explain even some of the more puzzling aspects of freeway traffic flow is tested here. Some of the observations furnished to this end pertain to dynamic features of traffic that have not been previously verified with data. These include findings that (a) freeway traffic can enter a semicongested state marked by a fast-moving queue in the passing lane with unqueued flow in the shoulder lane; (b) the possible devolution of traffic to a fully congested state when vehicle speeds in the passing lane drop below those in the shoulder lane supports the contention that freeway...

Stationary Models of Unqueued Traffic and Number of Freeway Travel Lanes

Anani, Shadi B.
Cassidy, Michael J.
2005

Occupancies and flows were jointly sampled from freeway segments in nearly stationary, unqueued traffic. When plots of occupancy per lane versus flow per lane were normalized by n (the number of travel lanes in the freeway segment from which a data set came), the plots took shapes that were piecewise linear in form (except for conditions that were near capacity) and were clearly influenced by n. Drivers adopted a higher speed (for a given occupancy) while traveling on segments of greater n. Yet, the speeds on these wider segments exhibited greater sensitivity: drivers began decelerating at...

TRICEPS: An ATMIS Field Implementation for Control and Evaluation: Final Report

McNally, M. G.
Rindt, C.
Logi, F.
2002

This report summarizes a comprehensive research project directed toward the development and implementation of an Advanced Transportation Management and Information System (ATMIS) as part of the Caltrans Advanced ATMIS Testbed Program at the Institute of Transportation Studies, University of California, Irvine. The primary goal of this project was to implement this prototype ATMIS, designated TRICEPS (Testbed Realtime Integrated Control and Evaluation Prototype System), in the Irvine sub-area of the Advanced Testbed network. This sub-area represents a well-defined freeway corridor with a...

Driver Turn-Taking Behavior in Congested Freeway Merges

Cassidy, Michael J.
Ahn, Soyoung
2005

Data from four merge locations in northern California and Toronto, Ontario, Canada, unveil a notable feature of driver turn taking. It was observed that queued vehicles from the on-ramp and freeway traffic streams entered a congested merge in some (nearly) fixed ratio that was independent of the merge outflow. Drivers in competing traffic streams thus entered the merge by adopting some definite turn-taking behavior, and this behavior was not influenced by the severity of the exogenous flow restriction from downstream. The findings validate part of an existing theory of merging traffic and...

On-Ramp Metering Experiments to Increase Freeway Merge Capacity

Cassidy, Michael J.
Rudjanakanoknad, Jittichai
2005

Observations of two freeway/on-ramp merges unveil the mechanism that causes their capacities to diminish when queues form just upstream. Field experiments at one of the sites demonstrate that by responding to occupancies measured near the merge, ramp metering can reverse this mechanism, or postpone its occurrence, and thereby generate higher merge capacities. Detailed observations at the second site imply that higher merge capacities can also be achieved using traffic control schemes that regulate inflows to the merge from the freeway shoulder lane. Collectively, the findings point to...