MDT extends I-15 65 mph zone south of Helena interchange

Drivers heading into Helena from the south now hit the 65 mph zone earlier on Interstate 15, with the lower limit starting half a mile south of the South Hills Interchange, Exit 190. The Montana Department of Transportation said the change shortens the stretch of freeway where motorists can accelerate before entering the city and brings the posted limit into line with Helena’s expanded urban boundary.

The adjustment is not just a signage change. MDT said the new boundary was approved by the Federal Highway Administration and by the Montana Transportation Commission on Dec. 11, 2025. Montana law requires interstate speed limits to drop to 65 mph in urban areas with populations above 50,000, and Helena’s growth has already pushed transportation planning beyond the city limits and into surrounding parts of Lewis and Clark County.

For daily drivers, the practical impact is immediate. Commuters, delivery trucks and visitors coming up I-15 from Jefferson County now have less distance to reduce speed before reaching the South Hills corridor and the city’s southern approach. Under Montana’s speeding fine schedule, drivers in the affected area can face fines of $40 for traveling 1 to 10 mph over the limit, $70 for 11 to 20 mph over, $120 for 21 to 30 mph over and $200 for 31 mph or more over the limit.

The state’s speed-limit guidance also defines daytime enforcement as one-half hour before sunrise to one-half hour after sunset, another detail drivers should keep in mind as traffic patterns shift around Helena’s southern edge. MDT lists Traffic and Safety Engineer Gabe Priebe and Lead Investigations Engineer Brenden Borges as the contacts for questions or comments about the reduction.

The timing lines up with broader planning work across the Greater Helena Area. The Greater Helena Area Metropolitan Planning Organization was formally established after the 2020 Census, when the Helena Urban Area surpassed 50,000 residents, and its long-range transportation plan is meant to guide more than 20 years of roadway, transit, bicycle and pedestrian investments across Helena, East Helena and nearby areas. Helena itself had 32,091 residents in the 2020 Census and an estimated 34,729 as of July 1, 2024.

The city is also looking at future access near the same corridor. In January 2025, Helena received a $1.3 million RAISE grant to plan and design the East Side Arterial Connector from the South Helena I-15 interchange to US Highway 12, including lane configurations, traffic control, pedestrian and bicycle facilities, transit and freight accommodations and infrastructure extensions. MDT says its I-15 Helena North project also begins south of the South Helena Interchange near the Lewis and Clark County-Jefferson County line and runs north toward the Lincoln Road Interchange, underscoring how central this stretch is to travel, safety and growth around Helena.