Traffic Operations and Management

Modular Composition of Synchronous Programs: Applications to Traffic Signal Control

Zennaro, Marco
Sengupta, Raja
2006

This paper describes a modular compilation scheme for distributed synchronous programming. The approach is first described mathematically and then implemented as a library to distribute Simulink (59). Application of the scheme is illustrated by developing a control system to coordinate traffic signals.

Macroscopic Relations of Urban Traffic Variables: An Analysis of Instability

Daganzo, Carlos F.
Gayah, Vikash V.
Gonzales, Eric J.
2010

For networks consisting of a single route the Macroscopic Fundamental Diagram (MFD) can be predicted analytically; but when the networks consist of multiple overlapping routes the flows observed in congestion for a given density are less than those one would predict if the routes were homogeneously congested and did not overlap. These types of networks also tend to jam at densities that are only a fraction of their routes’ average jam density. This paper provides an explanation for this phenomena. It shows that, even for perfectly homogeneous networks with spatially uniform travel patterns...

Multimodal Traffic at Isolated Signalized Intersections: New Management Strategies to Increase Capacity

Xuan, Yiguang
Gayah, Vikash
Daganzo, Carlos
Cassidy, Michael
2009

New ideas are explored for managing multimodal traffic on isolated approaches to signalized intersections. Strategies are proposed that both: segregate distinct modes along the approach, and more effectively resolve the disruptive capacity-reducing conflicts that arise between through moving and turning traffic traveling in adjacent lanes. The proposed schemes produce capacities that consistently and significantly exceed those of conventional intersection treatments, and reduce travel delays for all modes. Observations at a real intersection support these claims.

Bus Lanes with Intermittent Priority: Screening Formulae and an Evaluation

Eichler, Michael
Daganzo, Carlos F.
2005

This paper evaluates strategies for operating buses on signal-controlled arterials using special lanes that are made intermittently available to general traffic. The advantage of special bus lanes, intermittent or dedicated, is that they free buses from traffic interference; the disadvantage is that they disrupt traffic. We find that intermittent lanes, unlike dedicated ones, do not significantly reduce street capacity. Intermittence, however, increases the average traffic density at which the demand is served, and as a result increases traffic delay. These delays are more than offset by...

Deploying Lanes for High Occupancy Vehicles in Urban Areas

Cassidy, Michael J.
Daganzo, Carlos F.
2007

Simulations and field experiments in previous works suggest that a freeway’s general purpose lanes (those not dedicated to high occupancy vehicles) discharge vehicles from bottlenecks at an equal or higher average rate when one of the lanes is devoted to high occupancy vehicles than when it is not. This result was used in these previous works to develop formulae for the total discharge rate of bottlenecks, with and without dedicated lanes, as a function of the percentage of high occupancy vehicles in the traffic stream.This present paper extends these ideas by examining the effect of...

Multimodal Transport Modeling for Nairobi, Kenya: Insights and Recommendations with an Evidence-Based Model

Gonzales, Eric J.
Chavis, Celeste
Li, Yuwei
Daganzo, Carlos F.
2009

Traffic congestion is a growing problem in Nairobi, Kenya, resulting from rapidly increasing population and the crowding of motorized traffic onto a limited street network. This report includes analysis of the traffic conditions in Nairobi, the expected effects of further growth in demand, and a set of recommendations for how to improve the performance of the street network. Data describing motorized vehicle traffic was used to build a simulation model of Nairobi’s street network considering cars and matatus. This model was used to analyze traffic conditions at the city-scale under...

Unintended environmental impacts of nighttime freight logistics activities

Sathaye, Nakul
Harley, Robert
Madanat, Samer
2009

In recent years, the reduction of freight vehicle trips during peak hours has been a common policy goal. To this end, policies have been implemented to shift logistics operations to nighttime hours. The purpose of such policies has generally been to mitigate congestion and environmental impacts. However, the atmospheric boundary layer is generally more stable during the night than the day. Consequently, shifting logistics operations to the night may increase 24‐hour average concentrations of diesel exhaust pollutants in many locations. This paper presents realistic scenarios for two...

An analytical approximation for the macropscopic fundamental diagram of urban traffic

Daganzo, Carlos F
Geroliminis, Nikolas
2008

This paper shows that a macroscopic fundamental diagram (MFD) relating flow and average density must exist on any street with blocks of diverse widths and lengths, but no turns, even if all or some of the intersections are controlled by arbitrarily timed traffic signals. The timing patterns are assumed to be fixed in time. Exact expressions in terms of a shortest path recipe are given, both, for the street’s capacity and its MFD. Approximate formulas that require little data are also given.Conditions under which the results can be approximately extended to networks encompassing large city...

Deploying Underutilized Bus Lanes at Key Nodes in a Road Network

Guler, Ilgin
Cassidy, Michael
2010

The authors of this working paper explain that the operation of buses in mixed traffic flow can be impeded by congestion, leading to unreliable and slow service. Similarly, buses that stop frequently for passengers interfere with the flow of general traffic. Dedicated lanes provide a means for buses to bypass car queues, but in cases where bus flow is low, converting a general purpose lane to a bus-only lane will delay car traffic. The authors describe innovative schemes for deploying bus lanes to serve low bus demand intermittently. Strategies to deploy underutilized bus lanes will be...

Existence of urban-scale macroscopic fundamental diagrams: Some experimental findings

Geroliminis, Nikolas
Daganzo, Carlos F.
2007

A field experiment in Yokohama (Japan) reveals that a macroscopic fundamental diagram (MFD) linking space-mean flow, density and speed exists on a large urban area. The experiment used a combination of fixed detectors and floating vehicle probes as sensors. It was observed that when the somewhat chaotic scatter-plots of speed vs. density from individual fixed detectors were aggregated the scatter nearly disappeared and points grouped neatly along a smoothly declining curve. This evidence suggests, but does not prove, that an MFD exists for the complete network because the fixed detectors...