Driving Too Slow? You Might Be Breaking Montana Law

Is Driving Too Slow Illegal in Montana? Here's What the Law Says

The odds are strong that you’ve experienced the maddening crawl of being stuck behind a slow driver. Maybe it was on a winding, two-lane highway with endless no-passing zones. Or perhaps it was a motorhome laboring up a mountain pass or a farmer hauling a tractor or other equipment down the road.

It’s frustrating—no doubt about it. But here's the question: Is driving too slow in Montana actually against the law?

Read More: Driver Complains of "EV Hell" to Glacier National Park in Montana

Montana Highway Patrol Weighs In

Montana Highway Patrol tackled this common gripe back in 2018, in a video featuring Trooper Noah Pesola. According to Pesola, the topic of slow drivers is one of the most frequently asked questions the patrol receives. So, what does the law say?

Montana Code 61-8-311 addresses minimum speed regulations:

“A person may not drive a motor vehicle at a speed slow enough to impede or block the normal and reasonable movement of traffic except when reduced speed is necessary for safe operation or in compliance with law.”

In other words, if you’re puttering along and creating a rolling roadblock for no good reason, that’s not just annoying—it’s illegal.

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The “Four-Car Rule” on Two-Lane Roads

The law goes a step further. If you’re on a two-lane road and traffic starts stacking up behind you, you’re required to let others pass. Specifically:

“On a two-lane highway where passing is unsafe... the operator of a slow-moving vehicle behind which four or more vehicles are formed in line shall turn off the roadway at the nearest area where a sufficient and safe turnout exists in order to permit the vehicles following it to proceed.”

So, to be crystal clear: if you’ve got a line of four or more cars behind you, you must pull over at the next safe spot to let them go by. It's not just polite—it's the law.

Okay, what about on the Interstate?

Most drivers know that the left lane on the interstate is for faster-moving traffic, but can you get a ticket for dawdling along in the left-hand lane? The law is somewhat murky.

Montana Code 61-9-415 mostly refers to slow-moving vehicles like tractors, construction equipment, and horse-drawn buggies. These types of vehicles are required to keep as far to the right as safely possible—even on the shoulder if necessary. Specifically:

“On an interstate highway or on any other four-lane highway, a slow-moving vehicle... must be driven in the right lane as far to the right as possible, including the shoulder of the highway.”

What about regular passenger vehicles moving slowly in the left lane? Enforcement is more subjective. Trooper Pesola noted that it often comes down to an officer’s discretion. They have to weigh the safety risk of stopping a slow driver on the interstate versus letting them continue.

Bottom Line: Be Courteous

Legal or not, here’s a simple rule: If you're going to drive slow, stay in the right lane. And if you’re holding up a parade of cars on a two-lane, pull over and let people pass.

Everyone—including the guy stuck behind you—will thank you.