Originally developed by traffic engineer James Mackay in 1993 for the city of Denver, what has since become known as a “sharrow” (shared lane marking on streets) was a compromise from the start.
At the time, the city was unwilling to consider more bike-friendly lane solutions but game to consider a low-cost and easily implemented symbol. Case studies in the decades since, however, suggest that these well-intended markers could be doing more harm than good.
Featuring an abstracted cyclist inside an arrow, the original design came to be known as “bike in the house.” It was meant to point cyclists in the direction of traffic and encourage vehicles to share the road.
The more recent dual-chevron variant was named “sharrow” (a portmanteau of share and arrow) by Oliver Gajda of the City and County of San Francisco Bicycle Program. Perceived success in California led to these icons being deployed around the country, even finding their way periodically onto major highways (as shown above).
Sharrows have been shown to work well on some metrics according to studies commissioned by the Federal Highway Administration. The markings help get drivers outside of the dangerous “door zone” alongside parked cars, increase separation between moving cyclists and motorists and reduce wrong-way cycling on roads. In theory, these symbols also raise drivers’ awareness of bikers sharing their lane.
At least one study, however, concluded that sharrows did less to reduce collision-related injuries for cyclists on the streets of Chicago than either bike lanes or a complete absence of infrastructural intervention. Of course, this could be a city-specific result.
Some cities are still making the case that there is room on the roads for sharrows, at least with some improvements in place. Boston, for instance, has tested out what one reporter dubbed “sharrows on steroids” — basically sharrows reinforced with dotted lines within a wider vehicular lane — which may perform better. Meanwhile in Oakland, solid green paint has been deployed in places to indicate shared lanes, adding more visibility than periodic sharrow markings.
Perhaps these enhanced solutions will prove more effective. For now, though, sharrows alone are still too often used as an excuse to do less rather than more for urban cyclists. Cities committed to public safety also have a working model to draw upon: dedicated (especially separated) lanes for bicycle traffic have a long track record of success.
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The bright green does help with visibly, but in a wet or raining situation it also reduces friction. On more than one occasion I’ve almost slammed into something because a car swerved into the lane and my bike started hydroplaning
Bikes don’t hydroplane. The round profile and high pressure just doesn’t allow a layer of water to build up underneath the tire. The paint is simply slick and the water acts as a lubricant making it more slippery.
I’m a lifelong bike commuter in Seattle. We have had sharrows here for a couple of years. To me, they seem confusing at best – a traffic symbol is supposed to communicate information (stop, yield, watch for deer) and not make a vehicle operator wonder what they’re supposed to do. Does that mean bikes have the right of way? Does it mean that the driver should just be aware of bikes? Does it mean that there’s now a “war on cars?” (That’s not a joke, it’s a regular claim in the Seattle Times comment pages.) And that illustration of the bike with the arrows pointing three different ways – what the hell is that supposed to mean? Bikes can go any direction they want including over the curbs? Or, “cyclists be crazy, who knows what they might do!”
Pretty sure that in Seattle we would see the “cyclists be crazy” as a known fact. Come on admit that the majority of cyclists in Seattle don’t follow ANY of the actual road signs so it is irrelevant to them what the sign means. Hell based on actions I don’t believe they even know red lights mean stop. They think it means “dodge traffic as you cross here”
“At least one study, however, concluded that sharrows did less to reduce collision-related injuries for cyclists on the streets of Chicago ”
We have too many dumb-asses in Chicago that on one hand want to be treated like cars and ride directly in lanes (which I’m glad for them to be more visible) but then do not obey traffic signals, run stop signs and hang turns without stopping. You can’t have it both ways. I don’t need my car kicked when I pass you for riding like an asshole.
Ah sharrows: Literally pictures of people on bicycles being repeatedly run over by cars.
My review of the Chicago sharrow study is posted here:
https://figshare.com/articles/Review_of_Ferenchak_and_Marshall_sharrow_study/5480527
My main objection to the Chicago study is that the cyclist numbers and crashes were measured based on census block groups and cyclists ride outside of the census block group in which they live.
Kurt Kohlstedt stated “Of course, this could be a city-specific result.” Thank you for stating that opinion. If you look at Chicago in Google Maps, turn on Bicycling option, and drill down to the streets marked “bicycle friendly”, you’ll see the sharrows are painted in the door zone. So are the bike lanes. Another interesting fact from the study: during the after period of the study, the data shows the number of cyclists injured in crashes are: 21 of 100 in areas with no infrastructure, 25 of 100 in areas with sharrows and 34 of 100 in areas with bike lanes. The reason the study concluded that bike lanes are safer is because the crashes decreased MORE in areas with bike lanes from the before to after period. But they decreased almost the same in areas with no infrastructure.
The image of the sharrow on Portland’s 20s Neighborhood Greenway is misleading. In Portland, these sharrows are exclusively used for wayfinding.
I commuted by bike from downtown Seattle via busy streets for a couple of years. There’s no way that can be made safe. I was in what came close to being a nasty crash twice. Lane markers will do nothing to stop a car from smashing into a cyclist, much less a 10-foot-wide stretch city bus. Take it from me, almost getting side-swipped by the latter can be very scary.
When a dedicated bikeway is impossible, the best option is well-designed and dedicated bike greenways on residential side streets. There’s far fewer cars, and if the route is planned well, a cyclist can move along quite quickly.