• Volpe's Work
  • Volpe Subsites
    • GPS Activities
      • About GPS
      • Projects
      • Publications and Papers
      • Links
  • Technology Transfer
  • Volpe Technical Experts
  • Volpe Organizational Chart

Mobile Tracking System For Locomotives

Introduction

The Transportation Technology Center (TTC) in Pueblo, Colorado is a rail transit test facility owned by the United States Department of Transportation (USDOT) and operated by the Transportation Technology Center, Inc. (TTCI) for the Federal Railroad Administration (FRA). The TTC consists of 48 miles of railroad track dedicated to testing of rolling stock, track, communications and signaling equipment, and associated components. The three primary test tracks are the Railroad Test Track (RTT), the Facility for Accelerated Service Testing (FAST), and the Transit Test Track (TTT). The RTT is a 13.5 mile oval track used for testing trains up to speeds of 125 mph. The RTT also has a catenary system for testing of electric locomotives. The FAST is a 4.8 mile loop dedicated for testing of different types of rail components and cars under high axle loads. The TTT is a 9.1 mile oval with an overhead catenary and electrified third rail capability and is employed for the testing of rapid transit vehicles at speeds up to 80 mph.

Currently, only a broken rail detection system exists on the RTT. This system will provide limited track occupancy information by detecting loss of shunt, thus yielding a location resolution of 1 mile. Since this resolution granularity is unacceptable for obtaining real-time positioning, a more robust tracking system was desired for operational purposes. This lack of accurate location information and the need to explore tracking options for off track vehicles became the primary requirement for the development and implementation of a GPS-based position reporting system. To meet this objective, the Volpe Center is managing the design, installation, and testing of a Mobile Tracking System (MTS) at the TTC.

System Description

The MTS will consist of the following systems; 1) communications, 2) location information, 3) location display, 4) software drivers, and 5) associated hardware. A typical scenario will have mobile systems installed on a test locomotive on the RTT, a TTC maintenance vehicle, and an operations vehicle respectively. A central reporting station will be located in the Operations Command Center (OCC). This scenario is shown in Figure 1.

Each vehicle will have a location information system (LIS) consisting of a GPS/DGPS receiver capable of incorporating DGPS correction information. The location information will simultaneously be provided to the communications system and the location display system (LDS). The communications system will be an analog VHF (~171 MHz) data link connecting the mobile systems with each other and to the OCC. A time division multiple access reporting scheme will be employed to prevent collision of the transmitted data packets. The LDS will be capable of displaying a digital map of the TTC, a given vehicle's position on the map, and any associated text messages. The software drivers will be capable of supporting GPS data inputs received from the onboard GPS receiver and the data communications link. The software drivers will also be capable of uplinking and downlinking any text messages over the data communications link.

The proposed implementation of the MTS hardware is found in Figure 2. This involves a locomotive, two TTC vehicles, and the OCC. Each mobile unit will have a VHF data communications subsystem, a differential correction communications subsystem, a LIS, and a LDS. The OCC will have a VHF data communications subsystem and a LDS. All of the systems will have the software drivers.

On a parallel effort, the Volpe Center is managing the installation and testing of a low power Coast Guard compliant DGPS radiobeacon tower at the TTC. Once both of these systems are deployed, a positional accuracy of one meter root mean square will be achieved. The expected date of full operational capability for both of these systems is January, 1999. For additional information regarding either of these projects, please contact Adrian Hellman of the Volpe Center High Speed Ground Transportation Division at hellman@volpe.dot.gov.

View larger image of Figure 1.

Figure 1. A map of the TTC with the mobile units in a typical configuration.

View larger image of Figure 2.

Figure 2. Block diagram of the TTC mobile tracking system.