Can Trucks Drive in the Left Lane in Colorado?
Driving on Colorado highways comes with rules meant to keep everyone safe, especially for large commercial trucks. If you’ve ever been stuck behind a slow-moving semi in the left lane, you may have wondered: Can trucks legally drive in the left lane in Colorado? The answer is not simple, but drivers and truckers alike need to understand.
This article explains Colorado’s rules on lane usage for trucks, why these laws exist, and what happens when they are ignored.
What the Left Lane is Typically Used for
On most highways, the left lane is called the “passing lane.” It is intended for vehicles that are overtaking slower traffic. Once you’ve passed, you should return to the right lane. This rule isn’t just a suggestion—it’s part of Colorado law. In fact, Colorado passed a law in 2004 that specifically limits left-lane use unless a driver is passing. It’s called the “Left Lane Law.”
Colorado’s Left Lane Law Explained
According to Colorado Revised Statutes § 42-4-1013, drivers cannot stay in the left lane if they are not actively passing another vehicle. If the right lane is open and you’re not passing, you should move over.
The rules can be even more specific for large trucks. In certain areas, signs are posted that prohibit trucks from driving in the left lane entirely. These rules help keep traffic flowing and reduce the risk of accidents. Trucks are much larger and slower to stop than passenger vehicles, so limiting their left-lane access helps prevent slowdowns and crashes.
Are Trucks Ever Allowed in the Left Lane?
Yes, there are some situations where trucks can use the left lane in Colorado. But these are usually exceptions and not the norm.
For example, trucks may use the left lane:
- When they are passing a slower vehicle
- When the road has three or more lanes going in the same direction, and the far-left lane is not restricted
- If traffic or road conditions require it (such as accidents, road construction, or emergency vehicles blocking other lanes)
However, if signs say “No Trucks in Left Lane,” truck drivers must follow them. Ignoring these signs can result in fines and points on a driver’s record.
Where Are Left Lane Restrictions for Trucks Enforced?
In Colorado, left-lane restrictions for trucks are usually posted on highways where traffic is heavier or more dangerous.
One typical example is Interstate 70, especially in mountain areas where sharp turns, steep grades, and fast-moving traffic make it especially risky for large trucks to be in the left lane. Other highways, like I-25 and I-76, also have truck lane restrictions in certain areas. The Colorado State Patrol enforces these laws, and violators can face citations.
These left-lane rules are designed to avoid crashes and keep high-speed roads safe for all drivers. Slower-moving trucks in the left lane can cause dangerous traffic backups and sudden lane changes.
Why These Rules Matter for Safety
Large trucks driving in the left lane usually disrupt traffic flow. Trucks are bigger and heavier and take longer to speed up or slow down, making them less able to respond to emergencies or changing traffic patterns quickly.
If a truck is moving slowly in the left lane, it can cause other drivers to make risky maneuvers, such as weaving in and out of lanes to get around. It increases the chance of rear-end collisions and side-swipe crashes, which are often serious or even fatal when a large truck is involved. So these left-lane laws aren’t just about convenience—they’re a matter of public safety.
Contact our Denver Truck Accident Attorneys at Zaner Law Personal Injury Lawyers at (720) 613 9706
So, can trucks drive in the left lane in Colorado? Sometimes, but only under certain conditions. In most cases, they must stay in the right or middle lanes unless they are passing or responding to road conditions. Specific stretches of highway will even have signs banning trucks from the left lane entirely.
For more information, please contact the Denver truck accident lawyers at Zaner Law Personal Injury Lawyers to schedule a free initial consultation with a personal injury lawyer.
We are located in Denver, CO, and proudly serve all of Denver County.
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1610 Wynkoop Street, Suite 120.
Denver, CO 80202
(720) 613 9706
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About The Author
Kurt Zaner has earned national recognition for his innovative legal strategies, securing some of the largest verdicts in Colorado. He assists injured clients in Denver with personal injury cases, including car accidents, truck accidents, wrongful death, motorcycle accidents, and more. Click here to view some of the fantastic case results that Zaner Law has successfully handled.
Location: Denver, CO
