ST. LOUIS – Highway drivers deal with two situations on a daily basis: Passing a slower or driver or being passed by a faster driver.

All 50 U.S. states have laws when it comes to one driver passing another, but most laws generally support the idea that the faster driver should use the left lane to pass the slower driver on a highway.

Occasionally, you might notice that someone who passes you will hang out in the left lane for an extended period of time, even if there are no other vehicles in proximity to pass. You might know those kinds of drivers as “left-lane lollygaggers.”

It could make for an unsafe and frustrating situation when sharing the road, but as Nexstar affiliate KDVR tells us, there are some situations in which it’s not quite right to drive in the right.

The big question worth unpacking, at least for St. Louis-area drivers, when is it legal to drive in the left lane in Missouri and Illinois?


The most-recent statue in Missouri to address left-lane driving hasn’t been updated since 2010. If you use the left lane in the Show Me State legally, you shouldn’t be doing it for long.

Missouri State Statute 304.015 explains what should happen:

“All vehicles not in motion shall be placed with their right side as near the right-hand side of the highway as practicable, except on streets of municipalities where vehicles are obliged to move in one direction only or parking of motor vehicles is regulated by ordinance.”

Missouri State Statute 304.015

The statute says that the rule applies to drivers on all highways and public roads with sufficient width. The only exceptions are for passing a driver, avoiding construction, or nearing a left turn at an intersection.

The Missouri State Highway Patrol offers the following insight along highways:

“On highways with a total of four or more lanes (two or more lanes in each direction), a driver is mandated to drive in the right lane unless passing slower traffic, letting another driver have enough room to enter the highway safely, or preparing to make a legal left turn.”


The most-recent statue in Illinois to address left-lane driving hasn’t been updated since 2004. If you use the left lane in the Land of Lincoln legally, like Missouri, make sure it’s not for too long.

The Illinois Vehicle Code, specifically Article VII of Chapter 11, explains what should happen

“The driver of a vehicle overtaking another vehicle proceeding in the same direction shall pass to the left thereof at a safe distance and shall not again drive to the right side of the roadway until safely clear of the overtaken vehicle. In no event shall such movement be made by driving off the pavement or the main traveled portion of the roadway.”

Illinois Vehicle Code (Article VII of Chapter 11)

The statute notes in most instances that drivers should driver on the right side of the roadway. Though there are a few exceptions, like “when obstruction exists making it necessary” (like a stranded item) or when preparing for a left turn.

FOX 2 shared a friendly Illinois State Police in 2018 that offered the following insight on highways:

“Illinois law requires while traveling on an interstate you are to stay out of the left lane except when overtaking or passing another vehicle or moving over for a vehicle on the shoulder. This law does not apply to authorized emergency vehicles while engaged in official duties. In short, if you’re getting passed on the right, you’re wrong.”