Rail systems throughout the world use the Global Positioning System to track the movement of locomotives, rail cars, maintenance vehicles, and wayside equipment in real time. When combined with other sensors, computers, and communications systems, GPS improves rail safety, security, and operational effectiveness. The technology helps reduce accidents, delays, and operating costs, while increasing track capacity, customer satisfaction, and cost effectiveness.
Modern railways in several different countries are fielding Positive Train Control systems to prevent collisions, derailments, work zone incursions, and passage through switches in the wrong position. PTC is the combination of real-time location information with sophisticated command and control systems to monitor and control train movements.
A PTC system can automatically vary train speeds, re-route traffic, and safely direct maintenance crews onto and off tracks. In addition to enhancing safety, PTC increases track capacity by maintaining a constantly updated operating plan that optimizes rail use and flow.
The United States has mandated the use of PTC by 2015. U.S. PTC systems may use the Nationwide Differential Global Positioning System, an enhanced form of GPS that is accurate enough to tell whether a train changed tracks after going through a switch.
Rail systems that do not have PTC also gain benefits from GPS technology. GPS gives dispatchers and passengers more accurate information on train arrivals. It enables the automation of track surveying and mapping operations. GPS also allows the automation of track inspection systems that work much faster and detect more defects than human crews, saving time and money while improving safety.
"Knowing the exact location of our commuter trains has been a great benefit to our riders. Each of our commuter trains is fitted with a GPS receiver and a communications system that relays our position to our Internet site on a real time basis," said James W. Latchford, Road Trainmaster, AMTRAK/Virginia Railway Express. "From there it is available to any interested party who wants to know where the train is and when to expect it."
GPS also synchronizes the timing of railroad communication systems, including data transmissions for PTC, voice contact between locomotive engineers and dispatchers, and intermodal communications among trains, rail stations, ports, and airports.
Looking to the future, researchers are exploring ways to integrate GPS into vehicle-to-vehicle communication systems that could warn trains and cars of potential collisions at railroad crossings.
- Increased situational awareness for improved safety of trains and maintenance crews.
- Prevention of collisions, derailments, work zone incursions, and rail switch errors.
- Increased capacity and efficiency for all rail users.
- Dependable schedule and equipment location awareness.
- Automated track surveys and inspections.
- Time synchronization for communication systems.
Operated by Air Force Space Command's 50th Space Wing at Schriever Air Force Base, located east of Colorado Springs, Colo., the GPS constellation provides precise positioning, navigation and timing services worldwide as a free service provided by the U.S. Air Force, seven days a week, 24 hours a day. The GPS constellation is healthy, stable and robust with 12 GPS IIRs, seven GPS IIR-Ms, and 12 GPS IIF satellites on orbit providing precise global positioning, navigation, and timing services to users around the globe.
The latest generation of GPS IIF satellites provides improved signals to support both the warfighter and the growing civilian needs of a global economy. Featuring a new third civil signal -- L5 -- that benefits commercial aviation and safety-of-life applications, the GPS IIF series provides improved accuracy through advanced atomic clocks, and a longer design life than previous GPS satellites on orbit.
The Space and Missile Systems Center, located at Los Angeles Air Force Base in El Segundo, Calif., is the Air Force's center of acquisition excellence for acquiring and developing military space systems. Its portfolio includes the Global Positioning System, military satellite communications, defense meteorological satellites, space launch and range systems, satellite control networks, space based infrared systems and space situational awareness capabilities.