Traffic Operations and Management

A Problem of Limited-Access Special Lanes. Part II: Exploring Remedies via Simulation

Ni, Wei
Cassidy, Michael J.
Kim, Kwangho
Gu, Weihua
2015

Spatiotemporal analyses of freeway sites in Part I have shown that special-lane access points are prone to become bottlenecks. These can degrade traffic flows, sometimes in all lanes. Part II explores select impacts of re-designing the means of entering and exiting a special lane, and of altering the policy governing its use. Parametric tests were conducted using a computer simulation model that was calibrated to one of the sites studied in Part I; one with a buffer-separated carpool lane. Though less reliable than what might have been observed via experiments in real settings, the...

A Low-Cost Alternative for Higher Capacities at Four-way Signalized Intersections

Kozey, Peter
Xuan, Yiguang
Cassidy, Michael J.
2016

Protecting left-turn movements on all four approaches to a signalized intersection conventionally requires a minimum of two extra phases per cycle. Losses in capacity often result. Various intersection designs have been proposed to combat those losses. Perhaps the best known of these designs is the continuous flow intersection. It features specially-configured approach lanes and mid-block pre-signals. These enable opposing left-turn and through-moving vehicles to proceed through the intersection free of conflicts, and without need for additional protected-turn phases. The present paper...

Cordon Control with Spatially-Varying Metering Rates: A Reinforcement Learning Approach

Ni, Wei
Cassidy, Michael J.
2019

The work explores how Reinforcement Learning can be used to re-time traffic signals around cordoned neighborhoods. An RL-based controller is developed by representing traffic states as graph-structured data and customizing corresponding neural network architectures to handle those data. The customizations enable the controller to: (i) model neighborhood-wide traffic based on directed-graph representations; (ii) use the representations to identify patterns in real-time traffic measurements; and (iii) capture those patterns to a spatial representation needed for selecting optimal cordon-...

City-Wide Traffic Control: Modeling Impacts of Cordon Queues

Ni, Wei
Cassidy, Michael
2019

Optimal cordon-metering rates are obtained using Macroscopic Fundamental Diagrams in combination with flow conservation laws. A model-predictive control algorithm is also used so that time-varying metering rates are generated based on their forecasted impacts. Our scalable algorithm can do this for an arbitrary number of cordoned neighborhoods within a city. Unlike its predecessors, the proposed model accounts for the time-varying constraining effects that cordon queues impose on a neighborhood’s circulating traffic, as those queues expand and recede over time. The model does so at every...

Control Strategies For Transit Priority

Skabardonis, Alexander
1998

This report discusses the major factors which influence the benefits from transit priority. It reviews existing control strategies that have been implemented in signal controlled networks. A number of control strategies to improve transit performance are proposed along with an analysis technique to evaluate their effectiveness. The strategies were tested on a major arterial. Recommendations are given, based on the results.

Traffic Modeling To Evaluate Potential Benefits Of Advanced Traffic Management And In-vehicle Information Systems In A Freeway/Arterial Corridor

Gardes, Yonnel
1990

This study includes a literature review of existing traffic simulation models potentially suited for evaluating advanced traffic control strategies and in-vehicle information systems within an integrated freeway/ arterial corridor. Chapter 1 presents a literature review and identification of candidate models. Chapter 2 contains a preliminary screening of candidate models. Chapter 3 presents an in-depth evaluation of short list of models. And, Chapter 4 gives conclusions of the research and recommendations for future directions.

An Integrated Physical/link-access Layer Model Of Packet Radio Architectures

Polydoros, Andreas
1994

The goal of this effort is to devise and analyze an integrated Physical/ Link-Access Layer Model of packet Radio Architectures, with application to the PATH/IVHS (Intelligent Vehicle Highway Systems) communication sub- system design between vehicles and infrastructure, as well as between vehicles on the move. The present report contributes to a generic conceptual model for system evaluation which can be used for quantification of the interaction between network layers. The research tasks that have been performed for achieving the project objectives include collection of data requirements...

Achieving Higher Taxi Outflows from a Drop-off Lane: A Simulation-based Study

Yang, Fangyi
Gu. Weihua
Cassidy, Michael J.
Li, Xin
Li, Tiezhu
2020

Lanes used by taxis and other shared-ride vehicles at airports and rail terminals are often congested. The present paper examines congestion-mitigating strategies for a special type of lane inside of which taxis are prohibited from overtaking each other while dropping-off patrons. Taxis must therefore often wait in first-in-first-out (FIFO) queues that form in the lane during busy periods. Patrons may be discharged from taxis upon reaching a desired area near the terminal entrance. When wait times grow long, however, some taxis discharge their patrons in advance of that desired area. The...

Region-Wide Congestion Prediction and Control Using Deep Learning

Mohanty, Sudatta
Pozdnukhov, Alexey
Cassidy, Michael
2020

Traffic congestion is forecast for neighborhoods within a region using a deep learning model. The model is based on Long Short-Term Memory (LSTM) neural network architecture. It forecasts a congestion score, defined as the ratio of the vehicle accumulation inside a neighborhood to its trip completion rate. Inputs include congestion scores measured at earlier times in neighborhoods within a region, and three other real-time measures of regional traffic. The ideas are tested using Newell’s simplified theory of kinematic waves. Simplified street networks are featured first. Initial tests...

Synergies of Combining Demand- and Supply-Side Measures to Manage Congested Streets

Itani, Ibrahim
Cassidy, Michael J.
Daganzo, Carlos
2021

An agent-based, multichannel simulation of a downtown area reveals the impacts of both time-shifting traffic demand with congestion pricing, and supplying extra capacity by banning left turns. The downtown street network was idealized, and loosely resembles central Los Angeles. On the demand-side, prices were set based on time-of-day and distance traveled. On the supply side, left-turn maneuvers were prohibited at all intersections on the network. Although both traffic management measures reduced travel costs when used alone, the left-turn ban was much less effective than pricing. When...