Montana Department of Transportation

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Speed Limits

Daytime speed limits are in effect from one-half hour before sunrise to one-half hour after sunset. Nighttime speed limits are in effect at any other time. The following speed limits went into effect May 28, 1999. These speed limits apply unless a road or highway is otherwise posted for construction or a local limit.

Speed Limits (in miles per hour)
Type of Highway Cars and Light Trucks Heavy Trucks*
Daytime Nighttime Daytime Nighttime
Interstate 75 75 65 65
Interstate Within Urban Area ** 65 65 65 65
Two-lane 70 65 60 55
* over one ton manufacturer's rated capacity
** Billings, Great Falls and Missoula

Montana Codes Annotated - 61-8-303: Speed Restrictions

How do I get a speed limit changed?

The speed study is a common traffic investigation requested by the public and local governments. Although the initial request may come from a concerned citizen, Helena traffic staff typically contacts the appropriate local government in writing to request authorization to proceed with the speed study. It is department policy that all speed limit investigations must be conducted in cooperation with local officials. The request is placed on the list of speed study requests and processed in the order it was received unless a higher priority is assigned.

It usually takes 9-12 months to complete a speed study. This allows for data collection and comment from the public and local government prior to recommendations being presented to the Transportation Commission for action (MCA § 61-8-309).

For more information, please contact Doug Bailey at 406-444-6220.