Editor's note: This story has been corrected. A previous version indicated that motorcycle lane filtering is only legal on roadways with two or more lanes moving in one direction, similar to Utah's lane filtering law. In Colorado, though, lane filtering is indeed legal in a single lane, as long as the motorcycle rider doesn't cross the center line.
A new law took effect Wednesday that changes the rules for motorcyclists on some Colorado roadways. Effective Aug. 7, what’s called motorcycle “lane filtering” is legal in our state.
But what exactly does that mean?
Here’s what you need to know about the new law – SB24-079 – and what exactly it allows motorcyclists to do.
What is lane filtering in Colorado?
The simplest way to explain what lane filtering is, might actually be to first explain what it’s not. Lane filtering is not the same as what’s known as “lane splitting,” a practice in which a motorcyclist rides between lanes of moving traffic that’s legal in places like California.
Lane splitting has been illegal, and remains illegal, in Colorado – and equating one to the other is a “common misconception,” according to CDOT safety communications manager Sam Cole.
Colorado State Sen. Nick Hinrichsen, a prime sponsor of SB24-079, describes lane filtering as “a more conservative option” than lane splitting that only applies to “controlled traffic situations.” It is legal to lane filter in Colorado if all of the following apply:
- Other vehicles on the roadway are stopped
- The lane is wide enough to accommodate a motorcycle and another vehicle
- The motorcyclist travels 15 mph or less
- The motorcyclist cannot use the shoulder or enter a lane of oncoming traffic
- Conditions allow for safe passage by the motorcyclist
Lane filtering – and even lane splitting – are common practice around the world, Hinrichsen said. Utah, for example, has a lane filtering law very similar to Colorado’s. Colorado’s law took pieces from existing legislation in other parts of the country and the world.
For instance, many of the laws in Europe allow a motorcyclist to filter at 30 kilometers per hour (18.6 mph). A first draft of Colorado’s law allowed for 20 mph before it was revised down to 15 mph.
Why allow lane filtering?
While supporters of the law hope it leads to marginal improvements in areas such as traffic congestion and vehicle emissions, they say its primary goal is to protect motorcyclists – some of the most vulnerable motorists on our roadways.
A record 149 motorcyclists were killed in Colorado in 2022. That’s roughly 20% of the state’s traffic deaths from that year, despite motorcyclists representing just 3% of vehicles on our roads.
The lane filtering law takes aim at a particularly dangerous situation for motorcyclists.
“One of the riskiest times for a motorcyclist is, during a traffic jam, at the moment that traffic becomes backed up for all road users,” Hinrichsen said. “That is the point in which you're most susceptible to be involved in a rear end collision.”
Will lane filtering actually make our roads safer?
Colorado’s lane filtering law was written based on studies done on lane splitting in Australia, Europe and California. A few key takeaways from the official bill text:
- Two studies done in California between 2011 and 2015 found that lane-splitting motorcyclists are 43 percent less likely to be involved in a rear-end crash.
- A study done across five countries in Europe in 2009 found that 0.45% of motorcycle crashes involved lane splitting, and that motorcyclists were seven times more likely to be hit while stopped than they were to be hit while lane splitting.
- The Australia study deemed lane splitting to be a “low risk” maneuver.
We asked public safety officials in Utah and Arizona about the impact their laws have had.
In Utah, lane filtering became legal in 2019. Still, officials there tell us the law is too new to really understand its impact.
“We’re still in the data gathering phase, trying to figure out exactly how this has impacted safety,” said Jason Mettman with Utah’s highway safety office.
Part of the reason is that the crash form used by police officers across Utah still doesn’t have a place to indicate whether lane filtering played a role in a crash, Mettmann said. That checkbox will be added in 2025.
Unofficially, Mettmann told Denver7 crashes on roads where lane filtering was likely, have remained pretty flat.
“So as far as we can tell, we can't show a lot of safety that's occurred, but we can't show any negativity that's occurred from it either,” he said.
In Arizona, lane filtering was legalized in the fall of 2022. Its department of transportation didn’t have any specifics to share and suggested we reach out to local police departments.
Sgt. Justin Ramsay, who is in charge of the Glendale Police Department’s motorcycle division, spoke to Denver7 anecdotally, saying he and his department were not aware of any issues resulting from lane filtering.
What does lane filtering mean for other cars on the road?
In short, not much – if lane filtering is done correctly. Here's what our experts said:
“There really isn't anything a motorist specifically is going to have to do, except just know about the law and know that motorcyclists might be cutting between them and another vehicle,” Cole said.
“it's the motorcycle operator’s responsibility to make sure [lane filtering is] safe to do, that the conditions are what they need to be, that he [or she is] abiding by the law and [is] doing it safely,” Ramsay said.
How will Colorado measure success with lane filtering?
Colorado’s legislative website states that the law will be “repealed” on Sept. 1, 2027. Effectively, that means lawmakers are considering the law a three-year test, and will have the option in 2027 to put forth a new bill that extends and/or revises the law – or, of course, ban lane filtering altogether.
The official text of the act signed by Gov. Polis calls for a report by CDOT in January of 2027 with data on motorcycle rear-end and side-swipe collisions before and after the legalization of lane filtering.
“We’re going to see if the law’s being abused [...] We're going to see what those unintended consequences might be,” Cole said. “Do we have less crashes? Or do we have more because of the law? The law has seen promising results and other states are hoping it will have promising results here as far as reducing the number of injuries and deaths to motorcyclists.”
In Utah, the lane filtering law was extended for five years beyond its so-called sunset date in 2022 to allow for more data to be collected.
Adjusting to lane filtering will take time
As states find themselves in a years-long learning phase, and CDOT works to get the word out about Colorado’s new law, one thing is abundantly clear: Lane filtering is an adjustment.
“It just takes time for people to have experience with this and actually see it implemented, and then for them to understand the safety aspect of that,” said Lt. Cameron Roden with Utah Highway Patrol.
Hinrichsen said it’s an adjustment similar to those we’ve already seen happen. He said his hope is that lane filtering becomes what roundabouts have become since their widespread use started in the 1990s.
“I still remember many people at the time being uncertain about them. And there was some consternation and heartburn about it because it just wasn't something we're used to,” Hinrichsen said. “And now what we've seen is that they work. Roundabouts are safer than four-way stop intersections [...] I think most Coloradans have become really adapted to them. And given the option between four-way stop signs or a roundabout, the roundabout is almost universally preferred.”
“And my hope is that, given we've seen [lane filtering] work elsewhere, that [it’s] just something that’s part of the evolution of the way that we experience traffic – that maybe 10 years from now, or 20 years from now, this is something we look back on and don't even think twice about.”
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