Driving of motor vehicles - Maryland

Federal regulations

Maryland has adopted Part 392 of the Federal Regulations.

Applicability

Part 392 applies to vehicles with a gross vehicle weight rating or gross combination weight rating of 10,001 or more pounds as well as to anyone transporting hazardous materials requiring placarding.

Engine idling

A motor vehicle engine may not operate for more than five consecutive minutes when the vehicle is not in motion.

Exceptions — There are exceptions for:

• traffic conditions or mechanical difficulties over which the vehicle operator has no control;
• operating heating and cooling and auxiliary equipment installed on the vehicle;
• bringing the vehicle to the manufacturer’s recommended operating temperature; and
• when necessary to accomplish the intended use of the vehicle.

Speed limit

The speed limit is 70 mph on most rural interstates and 50 mph to 55 mph on other highways.