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...

Identifying Density-Flow Relations on Arterial Surface Streets

Ahn, Soyoung
Cassidy, Michael J.
2002

A simple car-following rule was verified by studying vehicles discharging from long queues at signalized intersections. These observations indicated that the time-space trajectory of a jth vehicle discharging on a homogeneous intersection approach was essentially the same as the j−1th vehicle except for a translation in space and time. This is in agreement with a simplified theory proposed by G.F. Newell. The finding indicates that the congested branch of a density-flow curve is linear in form.

Traffic Management System Performance Using Regression Analysis

Levinson, David
Chen, Wei
2006

This study can be viewed as a preliminary exploration of using regression analysis to evaluate long-run traffic management system performance. Four main traffic management systemsin the Twin Cities metro area --- Ramp Metering System, Variable Message Signs (VMS), Highway Helper Program, and High Occupancy Vehicle (HOV) System were evaluated based on multiple regression models. Link speed and incident rate were employed as the response variable separately. Consequently, regression analysis can be a simple and effective research method for testing the macroscopic association between traffic...

Traffic Data Measurement and Validation

Coifman, Benjamin
2001

Caltrans collects traffic data for many monitoring and control applications and the ultimate goal of the traffic surveillance system is to provide accurate data to these high level applications. The surveillance system includes data measurement, averaging and verification algorithms. This report presents improvements to many elements of the surveillance system. First, section 2addresses many shortcomings in average speed estimation at single loop detectors, as well as other sensors that estimate speed from average flow and occupancy. At the root of these problems is the fact that the...

Some Observed Queue Discharge Features at a Freeway Bottleneck Downstream of a Merge

Bertini, Robert L.
Cassidy, Michael J.
2002

Details of traffic evolution were studied upstream and downstream of a freeway bottleneck located near a busy on-ramp. It is shown that on certain days the bottleneck became active upon dissipation of a queue emanating from somewhere further downstream. On such occasions, the bottleneck occurred at a fixed location, approximately one kilometer downstream of the merge. Notably, even after the dissipation of a downstream queue, the discharge flows in the active bottleneck were nearly constant, since the cumulative counts never deviated much from a linear trend. The average bottleneck...

Complications at Off-Ramps

Cassidy, Michael
2002

You're driving along the freeway when suddenly everything slows down. A crash? A sudden overload of cars joining the freeway from on-ramps up ahead? Maybe. Sometimes the cause never reveals itself to you—inexplicably, everything just starts moving again. If this happens everyday in the same spot, you may develop a theory or two as to why it happens. Would it occur to you that the congestion might be caused not by too many cars getting on the freeway but b ytoo many cars trying to...

Testing Daganzo's Behavioral Theory for Multi-lane Freeway Traffic

Chung, Koohong
Cassidy, Michael
2002

This report describes the detailed, albeit still preliminary study of traffic on stretches of two different freeways. Both were plagued by merge bottlenecks. The first of these sites is the Gardiner Expressway, a 3.3 km long freeway stretch in Toronto, Canada. The site was selected because of its suitable geometry (i.e. its merge bottleneck) and its well-tuned loop detectors located upstream and downstream of the bottleneck. The site thus provided for an exceptionally good “laboratory” for testing Daganzo’s behavior theory of drivers (Daganzo, 1999). It turns out that the observations from...

Reduce Emissions and Improve Traffic Flow Through Collaborative Autonomy

Patire, Anthony D. PhD
Dion, Francis PhD
Bayen, Alexandre M., PhD
2024

This report explores opportunities for employing autonomous driving technology to dampen stop-and-go waves on freeways. If successful, it could reduce fuel consumption and emissions. This technology was tested in an on-road experiment with 100 vehicles over one week. Public stakeholders were engaged to assess the planning effort and feasibility of taking the technology to the next level: a pilot involving 1000+ vehicles over several months. Considerations included the possible geographical boundaries, target fleets of vehicles, and suitable facilities such as bridges or managed lanes. Flow...

Reduce Emissions and Improve Traffic Flow Through Collaborative Autonomy

April 30, 2024

Authors: Anthony D. Patire, Ph.D., Research and Development Engineer, PATH, University of California, Berkeley; Francois Dion, Ph.D., Research and Development Engineer, PATH, University of California, Berkeley; and Alexandre M. Bayen, Ph.D., Associate Provost for Moffett Field Program Development, University of California, Berkeley.

Abstract:

This report explores opportunities for employing autonomous driving technology to dampen stopandgo waves on freeways. If successful, it could...

Reduce Emissions and Improve Traffic Flow Through Collaborative Autonomy

Patire, Anthony D., PhD
Dion, Francois, PhD
Bayen, Alexandre M., PhD
2024

This report explores opportunities for employing autonomous driving technology to dampen stop-and-go waves on freeways. If successful, it could reduce fuel consumption and emissions. This technology was tested in an on-road experiment with 100 vehicles over one week. Public stakeholders were engaged to assess the planning effort and feasibility of taking the technology to the next level: a pilot involving 1000+ vehicles over several months. Considerations included the possible geographical boundaries, target fleets of vehicles, and suitable facilities such as bridges or managed lanes. Flow...