Driving of motor vehicles - New Hampshire

Federal regulations

New Hampshire has adopted Part 392 of the Federal Regulations.

Applicability

Part 392 applies to any self-propelled or towed motor vehicle used on a highway in intrastate and interstate commerce when the vehicle has a gross vehicle weight rating, gross combination weight rating, gross vehicle weight, or gross combination weight of 10,001 pounds or more, or is of any size transporting a placardable amount of hazardous materials.

Engine idling

A gasoline or diesel-powered motor vehicle may not idle for more than five consecutive minutes when the temperature is above 32°F. A vehicle may idle for up to 15 consecutive minutes when the temperature is between -10°F and 32°F.

Exceptions — There is no idling limit when the temperature is below -10°F and no nuisance is created. There are also exceptions for:

• traffic conditions over which the vehicle operator has no control;
• emergency vehicles;
• providing power takeoff for refrigeration, lift gate pumps, or other auxiliary uses;
• supplying heat or air conditioning for commercial passenger transportation;
• maintenance; and
• defrosting a windshield.

Speed limit

Reason and prudence are the guidelines for determining safe speed limits. Maximum speeds are 70 mph on I-93 from mile marker 45 to the Vermont border (effective 1/1/14), 65 mph on rural interstates, and 55 mph elsewhere, except where otherwise posted.