(a) General rule.--Every truck, other than a truck registered as either a Class I or Class II having a gross weight of 7,000 pounds or less, truck tractor and bus and any motor vehicle towing a trailer shall carry at least three portable emergency warning devices of a type specified by regulations promulgated by the department. The regulations shall be consistent with Motor Carrier Safety Regulations, Department of Transportation, Federal Highway Administration, Bureau of Motor Carrier Safety, section 393.95.

(b) When display required.--Whenever any vehicle of a type referred to in subsection (a) is disabled or stopped for more than ten minutes upon a roadway or shoulder outside of an urban district, or upon any divided highway, the driver of the vehicle shall display the portable warning devices of the type required under subsection (a) in such manner as the department shall direct by regulations.