U.S. railroads have begun curtailing shipments of hazardous chemicals ahead of a potential nationwide strike by workers, according to a major trade group representing oil refiners and petrochemical companies.

Grammer Industries Inc. announced it has acquired North Vass, N.C.-based Sterling Transport Co.

With its 180-degree bends, 7% grades, dangerous drop-offs and strong wind gusts, the hazardous material truck drivers hauling heavy petroleum loads who make the 9.5-mile journey though Colorado’s Loveland Pass call the drive a “white-knuckle experience.”

The National Tank Truck Carriers has requested that the Federal Motor Carrier Safety Administration grant commercial vehicle drivers who transport petroleum-based fuels a five-year exemption from a federally required 30-minute rest break.