CHICAGO (CBS) — The head of Metra’s board of directors has urged Congress to extend the deadline to install some costly safety equipment, or the commuter rail line and other railroads could be forced to come to a halt.

Metra Board Chariman Martin Oberman admitted it would be unthinkable for all railroad service to stop at the end of the year, but he insisted lawyers have told him that would have to happen if Congress doesn’t change the deadline for railroads to install positive train control systems.

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“It’s never happened, and it would be a complete disaster on individual lives, and on the economy if we were not allowed to operate; but if they don’t change the law, we will not have any options. We won’t be legally able to operate,” he said.

PTC systems are designed to automatically stop trains to avoid high-speed collisions or derailments, but Oberman said no such system is fully functional.

Earlier this month, Metra CEO Don Orseno wrote a letter to the chair of the U.S. Senate Commerce, Science and Transportation Committee, urging Congress to extend the Dec. 31 deadline for railroads to install PTC systems.

Chief executives from Union Pacific Corp, BNSF Railway, Norfolk Southern Corp., and CSX Transportation likewise have written Congress, threatening partial or total shutdowns Jan. 1 if the deadline is not extended.

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The threatened stoppage would halt the movement of everything from crude oil to perishable foods by the freight railroads. Orseno echoed the freight railroads, writing that Metra’s legal authority to operate would be in question.

“In the absence of an extension, there is a strong possibility that Metra will not be able to operate our trains beginning Jan. 1, 2016,” Orseno wrote. “Additionally, the two railroads with which we have purchase of service agreements — UP and BNSF — have stated that they do not plan to operate passenger rail until PTC is fully implemented and operational.”

The PTC system utilizes computes, radios and GPS to automatically slow or stop a train before it can become involved in a collision or derailment, even if the engineer falls asleep at the throttle or is disabled.

Orseno and the freight railroad chief executives wrote that installations are progressing, but are unlikely to be completed before 2018. Metra and the freight railroads have lobbied Congress for more than two years to extend the deadline.

He wrote that the fines alone would deal Metra a crippling blow. The Federal Railroad Administration (FRA) has said it will fine the railroads up to $25,000 per train if they operate without PTC.

“If these fines were to be paid by Metra, we anticipate they could cost our agency nearly $19 million per day,” he wrote.

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Metra alone is spending $350 million on PTC installation.