The NTSB put a newer version of the technology on its "most wanted" list of safety improvements when the list was created in 1990. The government has been funding demonstration projects for decades.
In the Los Angeles-area crash five years ago that prompted Congress to require PTC, investigators said the Metrolink commuter train's engineer was distracted by text messages, allowing the train to run through a red signal — precisely the type of accident the system is designed to prevent. The law gave railroads seven years and three months to install the technology.
The requirement applies to Amtrak and 25 commuter railroads, which together carry 564 million passengers annually, and the track they share with freight trains. It also applies to freight-only trains and tracks used to transport a category of hazardous materials poisonous to breathe, in response to a 2005 collision of two Norfolk Southern trains in Graniteville, S.C. A chlorine gas tank car was derailed and punctured, releasing a toxic cloud. Nine people were killed and hundreds injured. A textile plant that employed most of the town's residents was severely damaged and closed.
But pressure from industry has eroded the law's reach. Initial estimates were that positive train control would cover about 70,000 miles of track — less than half the nation's total. Now, that figure has shrunk to 50,000 miles. Regulators have given railroads permission to install less expensive PTC systems that won't prevent certain rear-end and low-speed collisions.
Freight railroads have campaigned to exclude tracks used only a few times a year to transport poisonous-to-breathe cargo. They also want to reroute trains containing such cargo to track shared with passenger trains, further reducing the amount of freight-only track that has to be equipped with PTC, said Grady Cothen, a former railroad administration official.
A weakness of the 2008 law is that it doesn't cover other types of dangerous cargo, including crude oil and ethanol, Cothen said. In July, an unattended train transporting 72 cars of crude oil came loose, hurtling down a 7-mile incline before derailing and igniting in the lakeside Quebec town of Lac-Megantic near the Maine border. The fiery explosion killed 47 people, and destroyed much of the town.
PTC wouldn't have prevented that accident, but the disaster underscores the risks of such shipments. U.S. railroads moved 178,000 crude oil carloads in the first half of this year — twice the number during the same period last year and 33 times more than during that period in 2009.
Metrolink and BNSF are on track to meet the deadline. Amtrak is also expected to meet the deadline, but only in its Northeast Corridor between Boston and Washington, and in Michigan.
While most railroad officials emphasize the train control system's cost, a significant side benefit not figured into cost-benefit calculations is that it can improve the efficiency of railroad operations, saving companies substantial sums, Cothen said.
PTC requires significant coordination between railroad companies operating on the same tracks since the software they choose must be compatible — a challenge to installation. Freight railroads also are still working on technical specifications, adding to delays. And some commuter railroads are struggling to find the needed radio spectrum to purchase, as well as the money to pay for both positive train control and other pressing repairs.
Szabo, the Federal Railroad Administration official, said he wants Congress to give the administration authority to grant case-by-case extensions. He said the key is finding an "appropriate balance between keeping feet to the fire" and making sure "it is done safely and reliably."