ITS Berkeley

Evaluating Steady-State Assumption for Highway Queueing System

Son, Young Tae
Cassidy, Michael J.
Modanat, Samer M.
1995

Stochastic queueing methods are often applied to highway systems to estimate performance characteristics such as delay and queue length.

Unique Bivariate Relationships in Highway Traffic

Cassidy, Michael J.
1996

Decision-Making System for Freeway Incident Response Using Sequential Hypothesis Testing Methods

Madanat, Samer M.
Cassidy, Michael J.
Teng, Hua-Liang
Liu, Pen-Chi
1996

Recent research in advanced traffic management systems has emphasized incident detection and response to mitigate nonrecurring congestion. Existing incident response decision-making algorithms do not account for the expected losses associated with false alarms, undetected incidents, and delayed incident response. A freeway incident response decision-making system based on sequential hypothesis testing techniques is presented. The primary feature of this decision-making system is that it minimizes the sum of the expected losses associated with false response, nonresponse, and delayed...

Application of Ordered Probit Techniques to Analyze Ratings of Blissymbol Complexity

Soto, Gloria
Cassidy, Michael
Madanat, Samer
1996

This paper explores the application of ordered probit modeling, an econometric technique commonly used for the analysis of rating data in situations when respondents are asked to rate items (e.g., an object, service, or product), one at a time. To demonstrate the application of this methodology, an existing data set, originally collected to measure the perceived complexities for an array of Blissymbols, was used. Findings from the use of the ordered probit model are compared with those resulting from the earlier research that used regression procedures. Results from the use of ordered...

Reexamining Vehicle-Actuation Strategies at Isolated Signalized Intersections

Cassidy, Michael
Chuang, Yu-Hao
Vitale, Jeff
1996

This paper uses simulation to assess intersection performance under enhanced vehicle-actuated signal control. The enhanced strategies seek to: (1) terminate green time in such a way as to promote use of the clearance interval by discharging vehicles.

Relation Among Average Speed, Flow, and Density and Analogous Relation Between Density and Occupancy

Cassidy, Michael J.
Coifman, Benjamin
1997

To counter the growing body of literature disputing that average vehicle speed is the ratio of flow to density, the relation is shown to hold as an identity when the variables are defined in the manner described by Edie. In similar fashion, the analogous relation between density and occupancy is shown to be true. These identities are illustrated with data measured by paired loop detectors, which underscores that Edie’s definitions are natural ways to treat the variables. The detector data are further used to show that any disputes surrounding the validity of these identities are largely...

Causes And Effects Of Phase Transitions In Highway Traffic

Daganzo, C. F.
Cassidy, M. J.
Bertini, R. L.
1997

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. Furthermore, all the evidence indicates that bottlenecks cause these transitions in a predictable way, and no evidence is found that stoppages (jams) appear spontaneously in free flow traffic for no apparent reason. The most salient phenomena observed at all locations are explained in terms of a simple theory specific to traffic.

Bivariate Relations in Nearly Stationary Highway Traffic

Cassidy, Michael J.
1998

This paper demonstrates that reproducible bivariate relations exist among traffic variables, such as flow and occupancy, when traffic conditions are approximately stationary. The inspection of cumulative curves of vehicle arrival number and vehicle occupancy has revealed that sustained periods of nearly stationary conditions do arise in the traffic stream. By plotting average values of the data corresponding to each nearly stationary condition, well-defined relations are observed. These scatterplots of near-stationary data are contrasted with plots of data that were measured over...

Design Of A Machine Vision-based, Vehicle Actuated Traffic Signal Controller

Cassidy, Michael
Coifman, Benjamin
1998

This project presents a signal controller algorithm to capitalize on the extended information provided by wide-area detection at isolated intersections. Using computer simulation, different control strategies are evaluated and the performance of the proposed wide-area detection system with conventional signal controllers is compared. The results indicate that wide-area vehicle actuated (VA) control can yield significant improvements over conventional VA control strategies.

Driver Memory: Motorist Selection and Retention of Individualized Headways in Highway Traffic

Cassidy, Michael J.
Windover, John R.
1998

The paper presents evidence that (1) drivers have different personalities in that they follow vehicles at different headways, and (2) drivers retain their personalities in that each driver tends to maintain his headway over space and, in some instances, drivers return to their headways after being forced by a traffic disturbance to alter them temporarily. This attribute, which we term driver memory, is revealed by visual inspection of modified curves of measured cumulative vehicle arrival number versus time.