Autonomous Dial-a-Ride Transit


 

The Corpus Christi Autonomous Dial-a-Ride Transit system, developed in partnership with the Volpe Center, relies on a network of on-board computers that communicate with each other to plan the most efficient transit service.

 

An ADART fleet covers

a large service area

withour any centralized

supervision. Like an

army of ants, the vehicles

accomplish their tasks

with no one in charge.

This article was originally published in the Winter, 2000, issue of the Volpe Journal, a publication of the Volpe National Transportation Systems Center located in Cambridge, MA.


In Corpus Christi, the Regional Transportation Authority has been exploring ways to use technology to provide more responsive and efficient transit service. Autonomous Dial-A-Ride Transit is one way to improve the efficiency of dial-a-ride transit services. As the name implies, dial-a-ride transit is an on-demand service, often in a bus or van, for customers who telephone their trip requests to a dispatching center. Riders primarily live in low-density areas not served by fixed-route transit, but dial-a-ride transit may also be used in more densely populated areas to serve customers, such as the elderly or disabled, not adequately served by conventional transit.

Because dial-a-ride services involve complex trips with multiple origins and destinations, efficient routing and consolidation of trips is essential for minimizing the per-trip cost. Since its introduction in the late 1960s, transit agencies have sought to increase the efficiency of dial-a-ride transit through the use of automated vehicle routing that would increase the number of riders per trip, thereby reducing the cost of individual service. Unfortunately, most dispatching remains computer assisted, rather than fully automated, and dial-a-ride transit services cost an average of $13 per trip, a figure that makes the service marginally competitive with conventional taxi service. In combination with other factors, there is a technical reason for this inefficiency: by the time demand reaches a level high enough to bring down the marginal cost of service, it also brings down the computer. Volpe Center analysts who have studied conventional dial-a-ride transit attribute this technical inefficiency to centralized and manually operated control centers.

In contrast, Autonomous Dial-a-Ride Transit (ADART) technology, developed by Dr. Robert Dial of the Volpe Center, encompasses a much higher level of automation, consolidating scheduling, fare collection, credit verification, and vehicle routing into a single automated system. Registered users simply call the on-board vehicle computer and enter their location and destination via a touch-tone keypad; the ADART system then develops an itinerary and states a pick-up and arrival time. When the vehicle reaches that point in the itinerary, the on-board computer displays the address and directions for quick reference by the driver. Because new users must identify a payment method when they register, there is no need for on-board fare collection. More importantly, computer-generated itineraries can dramatically improve the trip productivity, especially for those trips from dispersed residential areas to a fixed-transit station, a commercial or employment center, or a transfer location.

The Volpe Center's ADART design uses off-the-shelf computer and communications components to compose a system with emergent qualities of efficiency and improved service. The defining feature of ADART-the feature that enables full automation of the system-is that all dispatching, routing, and scheduling decisions are made by computers on board each vehicle, communicating with each other. These on-board computers assign trips and plan routes optimally among themselves. There is no dispatcher, and the driver's only job is to obey instructions from the vehicle's computer (and drive safely). Consequently, an ADART fleet covers a large service area without any centralized supervision. Like an army of ants, the vehicles accomplish their chore with no one in charge.

The Volpe Center's

Paul Bushueff envisions

"a collaboration

where all participating

organizations can

benefit from the

investments of others,

by pooling resources

and sharing costs."

The advantages of ADART have prompted many transit systems to evaluate its potential use. In Corpus Christi, the Regional Transportation Authority has begun implementation of an ADART system using funds from the Federal Transit Administration and assistance from the Volpe Center. The first phase of the project, conducted by the Center's Service Assessment Division, addressed the various component technologies (navigation, communication, routing, and scheduling) required by ADART. At the end of this phase, representatives from the Center, FTA, and the RTA concurred that existing technologies met or exceeded requirements for the system.

The Volpe Center is now taking ADART to the next level by producing a system capable of operating real vehicles on the streets of a real city. During Phase Two, staff members will produce a prototype version of ADART software for testing and performance analysis; the goal is to have two transit vehicles driving the streets of Corpus Christi "talking" to each other by September 2000. Once these tests have been successfully completed, the full range of ADART subsystems and capabilities will be tested in Phase Three; and full-fledged revenue service will be implemented in Phase Four.

Officials at the Corpus Christi RTA are enthusiastic about ADART, and the project has stimulated a great deal of national interest. Inquiries from transit providers nationwide have prompted the RTA to establish a peer-review panel to provide ongoing evaluation. Although the full-fledged introduction of ADART service may take some time, this innovative marriage of advanced technologies-conceptualized and developed by the Volpe Center-shows real promise for improved transit service at reduced cost. And while the benefits of increased routing productivity are not visible to most users, they benefit all potential transit customers. Increased efficiency on recurring trips can help the overall financial health of a transit agency, reducing its reliance on subsidies and allowing it to expand its services in other areas.


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Last modified: August 14, 2002