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Bike Lane Stripes:
Do they create better conditions for cycling?

Updated 2/8/2004

The city of Cary, NC recently began adding bike lane stripes to some existing low-traffic roads with wide travel lanes. Surface conditions on the rightmost portion of the roadway on these corridors have declined since the stripes were added, and some cyclists have reported increased harassment from motorists when riding farther left on the roadway.  Some of these roads were striped for bike lanes a year before these pictures were taken; others were striped just a few weeks before. Although some of these surface problems can occur on wide lanes without bicycle-specific stripes, the striping makes the problem much worse, as described below.

Note that these pictures are NOT intended to portray existing or typical road conditions in Cary. The Cary public works department has a good track record of taking action to improve roadway conditions when they receive requests and complaints from the bicycling public. The purpose of this page is to illustrate the inherent problems created by bike lane striping that result in greater complications for cyclists, maintenance crews, and police.   


The portion of the roadway used by automobile traffic is automatically swept clean by the movement of motor vehicles. But since the bike lane stripe encourages drivers to stay farther to the left even when there is no bicycle traffic, debris accumulates in the bike lane. In this picture the debris includes sand, pine cones, and sticks, but in other places one finds gravel, glass, and trash. Cyclists must operate in the travel lane to the left in order to stay out of the debris. (Creek Park Drive, 2002)

According to the Cary government web site, residential streets like these are swept once every three months. Note that debris volumes will vary depending on the amount deposited on the roadway by various sources including storms, sanding trucks, construction vehicles, and trees. These pictures were taken at times of significant debris because this makes the edge of the debris zone clearly visible. At other times, lower levels of debris that may be limited to an occasional patch of broken glass are much less visible, but still pose problems for cyclists. Such debris will be swept by cars out of the travel lane into the bike lane in the same locations shown in these photos. Because of this, many experienced cyclists prefer to keep their tires out of the likely debris zone even when no debris is readily visible. This minimizes the likelihood of puncture flats, skids, and falls, as well as the need for taking evasive action, but requires the cyclist to ride on the bike lane stripe or to its left, in the travel lane.


Sand, gravel, and storm debris have accumulated in this bike lane, although the travel lane to the left is clear of debris. (Crabtree Crossing Parkway, 2002)


Sand accumulation in a bike lane (Crabtree Crossing Parkway, 2002)


Because sand accumulation is much more slippery than clean pavement, sand accumulation can cause skids and falls. Falls are the leading cause of injuries to cyclists. (Crabtree Crossing Parkway, 2002)


Storm debris has been stacked in the bike lane area on several streets awaiting pickup. Cyclists operate in the ordinary travel lane. (Creek Park Drive, 2002)


Bike lanes appear to do little to discourage on-street parking in areas where residents find it useful. Cyclists must merge into the travel lane early and stay at least four feet away from parked vehicles in order to avoid being doored. (Creek Park Drive, 2002) These bike lane stripes have since been removed.


On-street parking was popular on this street before the bike lanes were striped. When Cary Police attempted to enforce parking prohibitions, residents complained to the city. The Cary Council consequently voted to remove the bike lane stripes on this street and allow on-street parking in the bike lanes in some other areas. (Photo: Creek Park Drive, 2002) These bike lane stripes have since been removed.

2/8/2004: Additional collector roads in Cary have been marked with segregation striping. These areas of the roadway have recently accumulated debris as shown in the following photos.


Debris and adjacent mailboxes mean that experienced cyclists stay to the left of this newly marked bike lane on Lake Pine Drive. (2004)


Most of Lake Pine Drive features sand accumulation in the 5' wide bike lanes on the day these photos were taken. Note that the rest of the roadway is clear up to the stripe. Fortunately, the normal travel lanes on this section of roadway are still wide enough for car drivers to pass safely, legally, efficiently, and without changing lanes, those cyclists who stay out of the debris zone. Note that although the ordinary travel lane here is about 14' wide, its full width is cleared by the sweeping action of cars, which use the full width of the lane as shown in the photo above. (2004)


Sand and parked cars fill the bike lanes on both sides of Lake Pine Drive near Maynard Road. (2004)


Sand and vegetative debris fill the area between the gutter and segregation stripes on Two Creeks. Note that the narrowing of usable pavement increases friction between drivers and cyclists when cyclists are operating outside of the debris zone. Also note that as the section of roadway to which motor vehicles are limited is narrowed, in this case to less than 24 feet, the clean section of roadway narrows in equal measure. (2004)


Two Creeks Road. The 10' wide travel lane to the left of the debris-filled-lane is too narrow for drivers of cars and trucks to pass cyclists who use the travel lane instead of the debris zone, because the median prevents drivers from moving far enough to the left or changing lanes. Compare the width of the cleared area here (10') with the cleared area of Lake Pine Drive (14') in a previous  photo to note the effect of the segregation stripe on the clean-swept width. (Photo: 2004)


Close-up of the segregated area of a typical section of Two Creeks Road. (2004)


Parked cars can also be found in the bike lanes on Two Creeks Road. (2004)


The purpose of this web page is to illustrate how bike lane stripes often fail to accomplish two of the things that their proponents claim as benefits: to create a clear space for cycling, and to make cycling easier for novices by telling them where to ride. In fact, the bike markings instruct novices to operate in a location that is often less safe for cycling than the rest of the roadway. The bike lane stripes on these roads encourage accumulation of debris in the roadway, and fail to discourage on-street parking. Although the cost of the striping projects themselves is significant, the city faces additional maintenance costs and enforcement costs if the bike lane area is to be kept clean and clear for cycling. Meanwhile, cyclists must know how and when to merge out of the bike lane and operate in the ordinary travel lane for their own safety. Additionally, motorists who see cyclists operating outside of the marked bike lanes often assume cyclists are not allowed to do so. This results in greater harassment of competent cyclists than on streets without such segregation markings.  Education is required to cycle safely on bike-laned streets and to reduce harassment by motorists. But with education, the lane stripes lose their appeal to cyclists. Many experienced cyclists prefer that streets like these not be marked with bike lane stripes, so that they can position themselves on the roadway according to context without the appearance of operating in violation of vehicle-specific traffic control devices.

Proponents of adding bike lane segregation stripes to quiet, low-speed residential streets often claim that such stripes improve safety by reducing collisions caused by errant motorists overtaking cyclists. However, in a study of six years of reported car-bike collisions in Cary, no motorist-error overtaking collisions were reported in lanes at least 12 feet wide. Less than one overtaking car-bike collision per year was reported for the entire city; each of the overtaking collisions occurred on arterial roads with narrow lanes (less than 12 feet wide) and posted speed limits of 45 mph. By contrast, the vast majority of reported car-bike collisions occurred at intersections, where bike lane stripes cannot reduce collisions, and may in fact increase collisions by encouraging road users to position themselves by vehicle type rather than by destination as required by state traffic law.

It has been claimed by some striping proponents that adding lane-narrowing striping to existing unstriped roads may reduce motor traffic speeds by reducing the perceived width of the roadway. Compelling evidence exists that contradicts to this claim. In 1999 the Institute of Transportation Engineers published  "Traffic Calming: State of the Practice", (FHWA-RD-99-135) a report on experiences with traffic calming in the US & Canada. From the section titled "Centerline and Edgeline Striping":

"Painting an edgeline several feet from the pavement edge has the effect of visually narrowing the roadway....In theory, the perceived narrowing could cause a modest speed reduction, just as a real narrowing causes a modest speed reduction. The theory is not borne out by empirical studies. Results from Howard County, MD, Beaverton, OR, and San Antonio, TX, suggest that vehicle operating speeds are as likely to increase as decrease with striping. One explanation is that centerlines and edgelines define the vehicle travel path more clearly, creating a gun barrel effect.

Results from the aforementioned studies could be dismissed because even with the narrowings, pavement and lane widths remained substantial. Yet, results from Orlando,
FL, where travel lanes were taken down to 9 feet, showed speeds to be unaffected (see figure 5.47).27 This psychoperceptioncontrol was not "tricking" anyone and hence was removed from both the centerline and edgelines."

Although many have tried, no scientific study has ever shown that segregation striping on ordinary streets improves safety for cyclists as compared to the same pavement space without the striping. For more on the controversy about the effect on segregation striping on cyclists, and preferable alternatives, see

Designing Wide Lanes

Critique of FHWA Bike Lane Versus Wide Curb Lane Study

How Wide Should a Wide Lane Be

Wide Outside Lanes are Superior to Bike Lanes

Bike Lane Contrarian

Implications of Universal Access Principles for Bicycle-Specific Roadway Markings