Colorado’s Lane Filtering Law Faces a 2027 Repeal

Colorado’s motorcycle lane filtering law expires on September 1, 2027 unless the legislature extends it. The statute that legalized the move also ordered a rear-end crash study by January 1, 2027, and that report is still not public.

The bet was narrow. Riders on two-wheeled bikes may creep past fully stopped traffic at 15 mph or less, on the left, in the same lane. Lane splitting through moving cars stays illegal. Year one of the pilot was also the deadliest year on record for Colorado motorcyclists, with 165 killed in 2024.

A Kill Switch Dated September 1, 2027

Governor Jared Polis signed Senate Bill 24-079 on April 4, 2024. The three-year filtering authorization took effect on August 7, 2024, and it repeals itself on September 1, 2027. CDOT has to analyze safety data and deliver a report to the General Assembly by January 1, 2027, so lawmakers have a few months to read it before the permission disappears.

The bill does not ask for a headline death total. It tells the department to compare motorcycle rear-end collisions before and after August 7, 2024, the severity of rear-end crashes in heavy traffic, and side-swipe collisions while overtaking at less than 15 mph. Until those three counts are published, the state is flying on a safety promise it has not scored.

Trooper Sherri Mendez of the Colorado State Patrol has said the point of the law was to “reduce the number of crashes involving motorcyclists because they were getting struck from behind” and to improve traffic flow. Glenn Davis, then CDOT’s highway safety office manager, put the same hope in plainer terms: keep much larger vehicles from hitting bikes from the rear.

THE FILTERING PILOT CALENDAR

1. April 4, 2024: Polis signs Senate Bill 24-079, limited to two-wheeled motorcycles.
2. August 7, 2024: Filtering becomes legal when same-direction traffic is fully stopped.
3. January 1, 2027: CDOT’s rear-end and side-swipe report is due to the legislature.
4. September 1, 2027: The filtering subsection is repealed unless lawmakers pass a new bill.

A Senate committee cut the original 20 mph cap to 15 mph before the bill reached the floor. That speed limit is now the bright line between a legal filter and a careless-driving case.

The House Passed the Bill 36 to 27

The Senate rolled through third reading with 28 yes votes, 2 no votes, and 5 members excused. The House was a different fight. On March 18, 2024, the chamber passed the bill 36 to 27, with 2 members excused. Nine votes decided whether Colorado would copy the tight mountain-west filter rules already on the books in Utah, Montana, and Arizona.

Sen. Nick Hinrichsen, a prime sponsor, called filtering “a more conservative option” than lane splitting because it applies only in controlled, stopped traffic. That is the wager in one sentence. Colorado would not legalize riding the paint between moving cars. It would let a bike creep to the front of a red-light queue, then fold back into the lane when the pack starts to roll.

The fiscal note predicted little new spending, because CDOT already holds crash files and would mainly have to sort them. The political cost sat in the House column, where almost as many members voted no as yes. That split is why the sunset exists. The permission was always a trial, and the trial still has a dated end.

2024 Set a Record 165 Motorcycle Deaths

CDOT counted 134 motorcyclist deaths in 2023, and 67 of those riders were not wearing a helmet. In 2024, the first season that included legal filtering after August 7, the count jumped 23 percent to 165, a state record that also appears in NHTSA’s fatality census. Preliminary CDOT figures for 2025 put the total at 147, an 11 percent drop from the record year and still above 2023.

The Colorado State Patrol documented 829 motorcycle crashes in 2024 and 354 reported incidents through mid-2025. Those two figures cover different windows, so they do not measure a full-year change. They also do not isolate rear-end hits in stopped traffic, which is the slice the statute actually cares about.

COLORADO MOTORCYCLIST DEATHS AROUND THE PILOT

Davis’s 2024 briefing already treated riders as a small fleet with a large share of the graves. Motorcycles were under 3 percent of vehicles and almost 20 percent of the deaths. Between 2021 and 2023, 26 percent of motorcycle traffic deaths involved an impaired rider. Speed and alcohol, not a stopped-traffic filter, still sit at the center of the fatality file.

Motorcyclists are among our most vulnerable road users. They represent less than 3% of the vehicles on the road but account for almost 20% of the deaths.

Glenn Davis, CDOT highway safety office manager, 2024 law rollout

A rear-end crash in gridlock can maim a rider without showing up as a record death year. The reverse is also true. A record death year can be helmets, impairment, and summer speed, and still say nothing useful about filtering. That is why the January report, not the 165, is the scoreboard the bill wrote.

Filter Legally and You Still Own the Crash

Colorado State Patrol’s current filtering page is blunt about liability. Filtering is optional. Traffic in the rider’s lane and the adjacent same-direction lanes must be stopped. If a crash happens in that gap, the rider would be at fault, because the motorcycle is the only vehicle moving.

Lane filtering is not required; it is an option for riders. The law requires traffic going in the same direction as the rider should be at a complete stop. Therefore, if there is a crash, the rider would be at fault as they would be the only vehicle moving.

Colorado State Patrol, lane filtering guidance

The legal pass is not a ride up the shoulder. CDOT’s own graphic says the shoulder is not used for passing. The rider stays inside the original lane, on the left of the stopped vehicle, and does not cross into oncoming traffic. When the stopped cars start to move, the bike has to stop filtering and rejoin the flow.

THE FIVE RULES THAT KEEP A FILTER LEGAL

• Stopped traffic: Vehicles in the rider’s lane and adjacent same-direction lanes must be at a complete stop.
• Lane width: The lane has to fit the motorcycle and the vehicle being passed.
• Speed cap: The motorcycle stays at 15 mph or less.
• Control: The rider has to pass safely and keep control of the bike.
• Left side only: Pass on the left and stay out of the oncoming lane; no right shoulder, and no pass to the right of a vehicle in the farthest right-hand lane on a highway that is not limited access.

Break those conditions and the maneuver is ordinary illegal passing, the kind that can be written as careless driving. Patrol guidance also tells riders to skip the move when they feel unsafe, when traffic is still rolling, when drivers look unpredictable, when the lane is too tight, when weather or visibility is poor, or when commercial vehicles fill a jammed road. That last caution is coaching, not a separate line in the statute, and it exists because a truck’s length and blind spots erase the gap a bike needs.

Col. Matthew C. Packard, chief of the Colorado State Patrol, has told riders to treat every queue as a fresh decision. Riding between vehicles puts the bike in a thin cushion, even when the cars are stopped. The legal right does not make the physics gentler.

What the I-76 Crash Showed About Splitting

The daily argument on Colorado roads is not the 15 mph creep at a red light. It is riders using the new permission as cover to move between cars that are still rolling. In August 2026, Colorado State Patrol dash camera video from I-76 in Denver showed a motorcyclist weaving through moving traffic and hitting the back of a sedan as it changed lanes, with patrol vehicles immediately behind. Patrol said the rider was lane splitting, which is illegal when traffic is moving.

That clip is the enforcement problem the sunset will have to confront. A three-year pilot only works if the public can see the difference the statute drew. Drivers describe bikes appearing beside them at speed in live lanes. Riders who never split still get painted with the same brush. Patrol has had to repeat the same sentence since the week the law took effect: filtering is stopped traffic; splitting is not filtering.

Packard’s September 2, 2025, warning ran in both directions. Aggressive driving includes a motorist tailgating, brake-checking, or blocking a motorcycle from re-entering a lane. It also includes a rider who treats the gap between moving cars as a private lane. On September 2, 2026, Durango Police restated the same split ahead of a motorcycle rally: filter through completely stopped traffic at no more than 15 mph, and do not pass between moving vehicles.

Lane splitting remains illegal in Colorado. If vehicles are moving, motorcyclists should not pass in the same lane or ride on the line between lanes. Riders' maximum speed is 15 mph or less. Know the law. pic.twitter.com/d1YKdfrMKp

— Colorado State Patrol (@CSP_News) September 9, 2025

The patrol’s September 2025 reminder still stands. If vehicles are moving, a motorcyclist should not pass in the same lane or ride the line between lanes. The maximum speed for a legal filter is 15 mph or less. The I-76 crash did not test that rule. It ignored it.

Utah Already Renewed a Filtering Pilot

Colorado did not invent the stopped-traffic filter. The enacted bill’s findings note that Montana, Utah, and Arizona had already legalized lane filtering, and that Utah extended its law after a sunset review in 2022. Colorado copied that shape: a low speed cap, a complete stop, a dated repeal, and a required agency report. California’s older practice of splitting through moving traffic was the thing Hinrichsen wanted to avoid.

THE WESTERN FILTERING PATTERN COLORADO JOINED

• Utah: Legalized filtering, then kept it after a 2022 sunset review, the model sitting in Colorado’s bill findings.
• Montana: Legalized filtering in the years before Colorado’s 2024 vote.
• Arizona: Legalized filtering in 2022, another neighbor named in the Colorado findings.
• Colorado: Two-wheeled bikes only, 15 mph, stopped traffic, report due January 1, 2027, repeal on September 1, 2027.

Utah’s renewal is the closest preview of what a successful Colorado report would buy. Lawmakers there looked at their own trial and voted to keep the tool. Colorado’s House barely created the tool in the first place. If CDOT’s rear-end and side-swipe tables come back noisy, or if the I-76 kind of splitting dominates the public memory, the 36-to-27 coalition does not have to repeal anything. It can sit on its hands until September 1, 2027, and the subsection dies on the date already printed in the statute.

Riders who want the permission to survive have a practical path that does not wait on the report. The State Patrol points people to Motorcycle Operator Safety Training courses at every skill level. CDOT notes that a rider who passes a MOST class can take the completion card to a driver’s license office and get an endorsement without another skills test. Training will not rewrite a rear-end table. It is the one lever riders control before the legislature reads that table.

Why Rear-End Crashes Are the Only Metric That Counts

The next official act in this story is a document, not a new slogan. CDOT already stores crash records. The workload the fiscal note described is sorting motorcycle rear-end collisions, grading those crashes in heavy traffic, and pulling side-swipe cases that happened under 15 mph, then lining the before-August-7 file against the after-August-7 file.

WHAT WE KNOW

• The deadline: The filtering subsection repeals on September 1, 2027, unless a new bill extends or rewrites it.
• The assigned test: The statute names rear-end collisions, their severity in heavy traffic, and low-speed side-swipes, not the annual death total.
• The death file: 165 riders were killed in 2024 and 147 in the preliminary 2025 count, after 134 in 2023.

WHAT IS UNCONFIRMED

• Rear-end trend: CDOT has not released the before-and-after rear-end and side-swipe comparison the law requires.
• Renewal votes: No 2027 reauthorization bill has been scored against those still-unpublished tables.

Lawmakers will get that comparison by January 1, 2027, if the department hits the date in the statute. They then have until September 1, 2027, to decide whether a two-wheeled bike may still creep past a stopped car at 15 mph. The 165-death year will be in the room. The I-76 video will be in the room. The number that matches the wager is the rear-end count CDOT has not yet put on the table.