Cross-cutting Issues

In this paper, we present adaptations of the A* algorithm for computing shortest paths between an origin node and a destination node in dynamic networks for one or multiple departure times. We give some properties of dynamic networks on which the dynamic adaptations of the A* algorithm are based. We develop efficient lower bounds on minimum travel times that exploit these properties. These lower bounds are then exploited to design efficient adaptations of the A* algorithm to solve instances of the one-to-one dynamic shortest path problem. The adapted algorithms are implemented and their computational performance is experimentally evaluated and tested. Using randomly generated networks, we show that the computer implementations of these adaptations can lead to a saving ratio of 11, in terms of number of nodes selected, and a saving ratio of 5 in terms of computation times for a network with 3000 nodes 10000 links and 100 time intervals. It is also shown that the savings increase with the network size.

Massachusetts Institute of Technology

Presented at the 10th ITS Annual Conference and Exposition, May 1-4, 2000 Boston, MA

This paper presents a research of an adaptive information system to provide designated information to selected pedestrian groups, aiming to reduce congestion and achieve better system efficiency. This approach, in a broader sense, suggests the possibility of changing travelers’ route-choosing behavior and improving transportation system effectiveness by distributing designed information to selected groups in an adaptive manner, rather than distributing homogeneous information to the whole population as in traditional information systems. Both conceptual analysis and simulations show that this approach could alleviate congestion and reduce pedestrian journey time in transit facilities.

Authors: Xi Zou, Lei Guo

Presented at the 18th World Congress on ITS, October 2011, Orlando, Florida

We study the problem of congestion in metropolitan areas and propose an adaptive Intelligent Transport System for Metropolitan Areas (ITSMA) – a traffic congestion management system that manages high occupancy vehicular traffic, commercial truck traffic and helps in coordination of commuter and ride share traffic. Most of these components are already available in parts – in form of stochastic algorithms for managing truck traffic, systems for ride share coordination using 5.9 GHz Vehicular Area Networks and numerous systems for HoV and toll management. The proposed ITSMA system consists of a prediction engine that takes multiple real time indicators to build a traffic congestion model. The decision engine component of ITSMA system takes the traffic congestion model, and using a database of previous actions and their impacts, proposes and implements actions in real-time. The outputs of the ITSMA system can be used to suggest routes, control high occupancy restrictions, traffic light durations, toll rates and access of commercial traffic. It can also aid in coordinating ride shares and public transportation units. Such a combined system can best leverage the investment at a metropolitan level and provide the best traffic congestion management solution.

Author: Amrinder Arora, DSc

Presented at the 18th World Congress on ITS, October 2011, Orlando, Florida

Adaptive signal control technologies have not been widely adopted and deployed in North
America. Millions of dollars are spent annually by agencies in order to time and retime signal
systems and at the same time millions of dollars are lost due to badly timed signal systems.
Why is this and what can be done about this in light of the rapid advancement in technology?
This paper provides an overview of adaptive systems that are available to the North American
traffic engineers that are ready for deployment. This paper will specifically highlight one
such system that automate the traffic signal timing process for arterials, an FHWA developed
package called ACS-Lite. This paper presents test results of evaluations done for the Idaho
Department of Transportation along the US-95 Corridor.

Transpo Group

Presented at the 15th World Congress on Intelligent Transport Systems, November 16-20, 2008, New York, New York

This paper describes a method by which the currently proposed Vehicle Infrastructure
Integration system can be used to provide adaptive control at signalized intersections.  
The approach uses the messages within the current draft SAE Standard J2735 to
request position data from the vehicles approaching an intersection equipped for VII.  
The system receives this data that defines the approaching vehicles trajectories and
uses it to change the signal controller to the next phase in order to minimize the delay.  
The proposed system would enable predictive adaptive traffic control without the use
of traffic detectors.

FreeAhead Inc.

Presented at the ITS America Annual Conference and Exposition, November 16-20, 2008, New York, New York