Traffic Operations and Management

Empirical Study of Ramp Metering and Capacity

Cassidy, Michael J.
Rudjanakanoknad, Jittichai
2002

Traffic data near the junction of a single-lane on-ramp (with a ramp meter) and a three-lane freeway were measured for six weekdays during the rush and studied. On each of these days, the merge became a bottleneck with queue discharge rates that were substantially lower than the flows that had passed the merge prior to the bottleneck's activation. On some days, these earlier high flows persisted for many minutes. The bottleneck always occurred when inflows from the on-ramp surged in the presence of high flows arriving from the freeway. Often, the on-ramp surges persisted for no longer than...

Measuring the influence of recurring sporting events on freeway characteristics

Seeherman, Joshua
Anderson, Paul
2017

Freeway traffic is subject to the effects of recurring and non-recurring events. Changes in the traffic stream as a result of recurring special events, specifically sports, is an area that is not well researched. This study examined freeway detectors adjacent to two baseball stadiums in California to analyze the contribution of a baseball game to freeway flow and occupancy for weekday evening games. In addition, hourly volumes on local rail transit were analyzed in the San Francisco case. Findings include a statistically significant effect of baseball increasing the flow by approximately 1...

Spatiotemporal Studies of Traffic Phenomenon on Freeways with Limited-access Special Lanes

Cassidy, Michael J.
Kim, Kwangho
2015

Most special-use freeway lanes in the US, whether reserved for carpools, toll-paying commuters or both, are physically separated from the adjacent regular-use lanes by some form of barrier. Vehicle movements in and out of a special lane of this type are permitted only at select access points along the route. The barrier at each select point might open for a distance of 400 m or so. Limiting access in this way is said to reduce the “turbulence” that might otherwise occur were the special lane not to have a buffer, such that vehicles could instead enter or exit that lane anywhere along its...

California’s Freeway Service Patrol Program:Management Information System Annual Report Fiscal Year 2018-19

Mauch, Michael
Skabardonis, Alex
2020

The Freeway Service Patrol (FSP) is an incident management program implemented by Caltrans, the California Highway Patrol and local partner agencies to quickly detect and assist disabled vehicles and reduce non-recurring congestion along the freeway during peak commute hours. The first FSP program was piloted in Los Angeles, and was later expanded to other regions by state legislation in 1991. As of June 2018, there were fourteen participating FSP Programs operating in California, deploying 328 tow trucks and covering over 1,823 (centerline) miles of congested California freeways. The...

In Traffic Flow, Cellular Automata = Kinematic Waves

Daganzo, Carlos F.
2004

This paper proves that the vehicle trajectories predicted by (i) a simple linear carfollowing model, CF(L), (ii) the kinematic wave model with a triangular fundamental diagram, KW(T), and (iii) two cellular automata models CA(L) and CA(M) match everywhere to within a tolerance comparable with a single "jam spacing". Thus, CF(L) = KW(T) = CA(L,M).

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.

Safety and Other Impacts of Vehicle Impound Enforcement

Cooper, Douglas
Chira-Chavala, T.
Gillen, David
2000

California vehicle impound law took affect on January 1, 1995. The law allows a police officer to seize a vehicle operated by a person whose license is suspended or revoked or who has never been issued a license. The seized vehicle shall then be impounded for 30 days. In California, a driver must be stopped for some other infraction before his/her license can be checked. The City of Upland, located in western San Bernardino County, has a population of 67,453 residing in a 15.2 square-mile area. The city’s 169 miles of roadways support about 600,000 vehicle-miles of travel daily. Upland...

Evaluation of Coordinated Ramp Metering (CRM) Systems in California

Mauch, Michael
Skabardonis, Alexander
2021

Freeway on-ramp metering (RM) has been extensively used as a traffic control strategy to regulate the entry of the on-ramp vehicles to prevent congestion at the freeway merging areas and preserve the freeway capacity. Benefits of RM include improved freeway travel times, improved travel time reliability, and accident reductions. Fixed-rate ramp metering strategies are based on historical data and implemented by time of day. Traffic responsive RM strategies are based on real time freeway traffic data provided by loop detectors at the vicinity of the on-ramp. Coordinated RM determine the...

California’s Freeway Service Patrol Program: Management Information System Annual Report Fiscal Year 2016-17

Mauch, Michael, PhD
Skabardonis, Alex, PhD
2018

The Freeway Service Patrol (FSP) is an incident management program implemented by Caltrans, the California Highway Patrol and local partner agencies to quickly detect and assist disabled vehicles and reduce non-recurring congestion along the freeway during peak commute hours. The first FSP program was piloted in Los Angeles, and was later expanded to other regions by state legislation in 1991. As of June 2017, there were fourteen participating FSP Programs operating in California, deploying 324 tow trucks and covering over 1,718 (center-line) miles of congested California freeways. The...

Critique of a Freeway On-Ramp Metering Scheme and Broader Related Issues

Cassidy, Michael J.
2002

Offered here is a critique of a simple scheme recently proposed for metering freeway on-ramps. An earlier report of this scheme's potential for reducing commuter delay is shown to be exaggerated. The discussion makes clear that to reduce delay, metering should increase the rates at which commuters exit the freeway. The scheme critiqued here, as well as other well-known metering algorithms, are shown to have deficiencies in this, particularly when the freeway is plagued by a diverge bottleneck with a congested off-ramp. Other more effective schemes for reducing the delay caused by these...