If you ask 50 people about Colorado’s rules for lane filtering, you might get 50 different answers.
But it is not California-style lane splitting, where motorcyclists can zip between lanes of traffic at 70 mph on the interstate. Semantics matter in this case even though many people use the terms interchangeably.
It is not a widespread practice, which likely adds to confusion about what it is and why Colorado has added a law to try it out. Only five other states allow lane filtering, and they have varying rules. California is the only state that allows lane splitting.
In all cases, the idea behind it is that it makes roads safer for motorcyclists, particularly in lines of stop-and-go traffic or at lighted intersections where they are vulnerable to rear-end collisions.
Motorcycle fatalities accounted for 24% of all highway fatalities in Colorado in 2024 even though motorcycles are only 3% of all registered vehicles, according to CDOT data. In the last 10 years, more than 100 motorcycle fatalities have occurred annually, and they hit a high of 165 in 2024.
Those statistics led the Colorado legislature to legalize lane filtering under certain conditions – we’ll get to those in a moment – for three years. The practice started in August 2024, and the law will expire in September 2027 unless it is extended.
In the meantime, the Colorado Department of Transportation will gather data on rear-end and side-swipe collisions involving motorcycles and compare it to what happened before the law went into effect.
So the law must prove itself by showing that it made the roads safer for motorcyclists.
CDOT and the Colorado State Patrol have put a lot of effort into explaining the law and what motorcyclists are allowed to do. Trooper Gabriel Moltrer, a CSP spokesman, explained that five rules must be followed during lane filtering:
- Vehicles must be at a complete stop and headed in the same direction;
- The lane must be wide enough to fit the vehicle and the motorcycle;
- The motorcycle must go 15 mph or less while passing;
- The motorcycle must pass safely and maintain control, and
- The motorcycle must pass on the left and remain in the traffic lane.
This means that at an intersection, for example, motorcyclists can move to the front of the line and when the light turns green they can proceed across without being between vehicles. The same goes for backups on a highway when traffic has come to a standstill.
“Drivers also have to understand this is a law now,” Moltrer said. “As long as the five criteria are being met, they should not be tailgating or intentionally blocking a motorcycle from re-entering the lane.”
Motorcyclists traveling through other states should note that lane filtering is not legal in most. In states where it is legal – Arizona, California, Hawaii, Minnesota, Montana and Utah – the rules vary significantly so riders should check out the specifics before they hit the road.
The State Patrol also encourages motorcyclists to take a Motorcycle Operator Training Course (MOST), even if they already have the required motorcycle endorsement on their license. MOST has basic, advanced and three-wheel motorcycle classes.
Colorado does not require motorcyclists to wear helmets unless they are under 18. Passengers under 18 also are required to wear a helmet. Motorcyclists are required to wear eye protection – goggles, sunglasses or a helmet shield.
Colorado’s mountain passes can be as challenging to motorcyclists as they are to some drivers, and Moltrer suggest the usual precautions of scoping out the planned route and being prepared for sudden weather changes.
CDOT has suggestions for motorcyclist to help them stay safe on Colorado roads:
- Get training, especially if you’re new to riding. But even if you’ve been at it a while a course to brush up on your skills might be a good idea.
- Keep your speed down and obey all rules of the road.
- Gear up – always wear protective gear, including a helmet.
And drivers of other vehicles can play a role in keeping motorcyclists safe:
- Always check blind spots for motorcycles.
- Always look twice when pulling onto a roadway. Motorcycles can be hard to see.
- Avoid distractions.
- Never follow motorcycles too closely.
Researched and written by Sue McMillin