Rail systems throughout the world use GPS 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 (PTC) 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.

PTC is not yet universal, but many rail systems without it also benefit from GPS technology. It 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.

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.