Colorado’s Express Lane Law Is About More Than a $75 Fine

If you drive I-25, the C-470, or US 36 regularly, you’ve watched it happen. A car drifts out of the express lane across a solid white line, cuts back in a quarter mile later, then darts out again to gain a few car lengths. It’s common, and until recently, largely unenforced.

That changed on January 1, 2025. Colorado began issuing civil fines to drivers who enter or exit express lanes outside of designated areas in three major corridors: Central 70, the I-25 South Gap, and US 36. The fine is $75 — nothing ruinous. But the fine is actually the least important part of the story for anyone who gets hurt when that weaving causes a crash.

The Law and Why It Exists

Colorado’s express lanes operate at speeds and volumes that create serious hazards when drivers cut across solid white lines outside the designated merge zones. The speed differential between express lanes and general-purpose lanes can be significant; vehicles in express lanes often move faster, and the transition from one lane to the other outside a controlled merge point creates unpredictable conflict points.

CDOT has been direct about why the rule matters. The technology used to detect violations, sensors, cameras, and software, first deployed on the I-70 mountain corridor, had already reduced weaving violations by 80 percent in corridors where it was installed before the fines began. According to CDOT, drivers weaving in and out of express lanes cause crashes every year.

During the 30-day grace period before fines took effect on January 1, 2025, Colorado issued more than 23,000 warnings. The scale of that number suggests how common the behavior had become.

Scott O’Sullivan, who was interviewed by Denver 7 when the law took effect, put it plainly: “In the 25 other states that have passed it, it actually results in almost an immediate 10% decrease in fatalities on the road. And so in Colorado, that means between 46 and 50 people will be here this time next year because this law passed.”

The Legal Significance: Negligence Per Se

Here’s what matters most if you’ve been hurt by a driver who was weaving illegally in an express lane: in Colorado, a traffic violation that causes an accident can establish what’s called negligence per se.

Under Colorado personal injury law, when a driver violates a safety statute — a law specifically designed to protect people on the road — and that violation causes a crash, the driver can be found negligent as a matter of law. You don’t have to argue about whether a reasonable person would have done what they did. The violation of the specific rule is itself evidence of negligence.

The express lane weaving law is exactly the kind of safety statute that supports a negligence-per-se argument. It was enacted to prevent crashes caused by unpredictable lane transitions in high-speed corridors. When a driver breaks that rule and someone gets hurt, the legal connection is clear and direct.

“The reason these traffic laws matter in an injury case is that they establish a standard,” Scott says. “The law said you cannot cross a solid white line in these corridors outside of the designated areas. That rule existed to protect other drivers. When someone broke it, and you got hurt, that matters in court and settlement negotiations too.”

What This Looks Like in Practice

Picture a Friday afternoon on I-25 South. Traffic in the general-purpose lanes is moving slowly. A driver decides to jump into the express lane by crossing a solid white line, realizes they missed their exit, and cuts back across to the right. In doing so, they misjudge the speed of a vehicle already in that lane. The sideswipe happens at 60 miles per hour.

Before January 2025, that driver had violated a general duty to drive safely, which is the basis of any negligence claim. But now there’s something more specific: they violated C.R.S. § 42-4-1012, the express lane statute, which was enacted specifically to prevent this type of hazard. Their violation of that law is direct evidence of fault.

Insurance adjusters know this. Defense attorneys know this. When there’s a documented traffic violation connected to a crash, it changes the dynamics of every negotiation that follows.

Evidence in Express Lane Cases

One feature of the express lane enforcement system that benefits injury victims is the detection infrastructure itself. CDOT’s sensor and camera system was designed to identify and document violations. In some cases, that means there’s an official record — potentially including imagery — of a vehicle crossing a solid white line outside a designated area.

Beyond that official record, other evidence worth preserving quickly includes:

•       Your own dashcam footage, if you have it
•       Footage from nearby commercial properties or other vehicles
•       CDOT traffic camera footage (subject to retention periods)
•       Police and crash reports documenting the point of impact and lane positions
•       Witness contact information from others who observed the driving behavior before the crash

The Bigger Context

This law is relatively new, and most Colorado drivers have a vague sense of it. They may know there are fines now, but they try to remember not to cross the solid lines. What far fewer people understand is the legal consequences when the rule is broken, and someone is hurt.

The shift that happened on January 1, 2025, wasn’t just about fines. It was about the formal recognition, backed by enforcement infrastructure, that weaving in and out of express lanes is dangerous, unlawful, and it’s legally actionable in a way that strengthens the position of anyone who gets hurt.

If you were in an accident on one of Colorado’s express lane corridors and the other driver crossed a solid white line outside a designated area, that detail is worth discussing with an attorney. It may be more significant to your case than you realize.

Give us a call or text at 303-388-3504 to discuss. Advice is always free.

Scott O’Sullivan has represented injured Coloradans from his Denver office for over 25 years. If you were hurt in a highway accident in Colorado and want to understand your legal options, call The O’Sullivan Law Firm at (303) 388-5304. The consultation is free, and you’ll speak directly with an attorney.