Today, days after a deadly Amtrak derailment in Philadelphia, the Federal Railroad Administration has announced an emergency order instructing the railroad to expand use of its automatic braking system. The system, called Automatic Train Control (ATC), was already in place on the southbound side of the tracks at Frankford Junction in Philadelphia, along Amtrak's heavily used Northeast Corridor. The order, which will "be formalized in the coming days," calls on Amtrak to "immediately" activate the system along the northbound tracks at Frankford Junction.

ATC measures the speed of trains along a section of track and can send a warning to the engineer if it is moving too fast. If the engineer does not respond, the system can automatically apply the brakes. According to The New York Times, authorities said in the aftermath of the derailment that ATC was only active along one side of the tracks because the speed limit right before the turn is higher for southbound trains (110 miles per hour) than northbound trains (80 mph). The turn, among the sharpest along the Northeast Corridor, has a posted speed limit of 50 mph. Northeast Regional 188 was measured travelling 106 mph in that zone before the crash.

The ATC system is an older safety measure than Positive Train Control (PTC), which has received plenty of attention following the accident on Tuesday. In 2008, Congress ordered railroads across the country to install the system by the end of this year. Amtrak already has the system active on many sections of track along the Northeast Corridor, and it expects to have its rollout complete this year. Other than the order to install ATC, the Federal Railroad Administration also instructed Amtrak to analyze all turns on the Northeast Corridor and add the system to turns where trains must decelerate from high speeds. It also called for improved speed limit signage along the route.