CA AB172

Authorizes motortrucks and truck tractors with 3 or more axles, or those drawing other vehicles, to drive up to 65 miles per hour in rural areas instead of the existing 55 miles per hour limit.

Maintains the 55 miles per hour speed limit for these vehicles in non-rural areas and for other regulated vehicles including passenger vehicles towing trailers, school buses, farm labor vehicles, and vehicles transporting explosives.

Allows the Department of Transportation and local authorities to set lower speed limits (50, 45, 40, 35, 30, 25, or 20 mph) on descending grades based on engineering studies and traffic surveys.

Makes conforming changes to Vehicle Code sections regarding taillamp and reflector requirements for affected commercial vehicles.