In my own analysis of car-bike crashes in Cary, NC, I saw that about 94% of collisions were at driveways and intersections ... and that operation on the sidewalk correlated with a disproportionate share of these collisions. This compares well to other studies that show sidewalk cycling to greatly increase the risk of collisions at intersections. Also, collisions with dogs, pedestrians, and street furniture make the rate of non-motor-vehicle-related injuries much higher on sidewalks.

I have conducted a typology and analysis of all police-reported car-bike collisions for the last six years here in Cary, NC, population 100,000.

The Cary Police department provided me 75 Cary Police reports dated from March 7, 1997 to November 21, 2002. Of these 75 reports, 73 included enough information to determine the positions and directions of the vehicles during the collision. Note that many of these collisions involved injuries but none involved fatalities. I classified these 73 collisions by the following types, in order of frequency, which I believe are useful for understanding the problems and potential preventative measures. Note that a couple of these numbers may change slightly when further investigation is completed:

WRONG WAY: 36 collisions (49%) involved bicyclists traveling on the left half of the highway against the ordinary flow of vehicular traffic. Nearly all of these bicyclists were operating on the sidewalk prior to the collision. 30 of these wrong-way bicyclists were struck by automobile drivers who were turning right onto the roadway from a stop sign, red light, or driveway. These drivers were probably looking to the left prior to the collision.

RIDE OUT: 12 collisions (16%) involved bicyclists who rode out across the roadway or private vehicular area where the motor vehicle driver had the legal right of way and could not stop in time. Most of these collisions occurred at intersections or driveways.

LEFT CROSS: 7 collisions (9.6%) involved motor vehicle drivers who turned left across the path of the cyclist (who was traveling in the correct direction for vehicular traffic, on the opposite side of the road from the oncoming motorist) and violated the cyclist's legal right of way.

RIGHT HOOK: 5 collisions (6.8%) involved motor vehicle drivers who were traveling in the same direction as the bicyclist when the motor vehicle drivers turned right and collided with the bicyclist. Four of these bicyclists were operating on the roadway; one was operating on the sidewalk prior to the collision. One of the bicyclists on the roadway was attempting to overtake the automobile driver on the right. One of the motor vehicle drivers attempted to turn right from the left through lane immediately after passing the bicyclist who was using the right through lane.

DRIVE OUT (PROPER DIRECTION CYCLIST): 5 collisions (6.8%) involved motor vehicle drivers who drove out across the roadway where the cyclist (who was operating in the correct direction for vehicular traffic on that side of the highway) had the legal right of way. Four of these bicyclists were operating on the roadway; one might have been on the sidewalk but the police report does not specify.

PASSING TOO CLOSELY: 5 collisions (6.8 %) involved motor vehicle drivers who attempted to pass bicyclists at unsafe distance, resulting in collision. More on these collisions follows below.

BICYCLIST LOSES CONTROL: One collision (1.4%) occurred when a cyclist lost control and crashed into the side of a motor vehicle that was stopped at a stop sign.

BICYCLIST TURNS LEFT FROM CURB: One collision (1.4%) occurred when the cyclist attempted to turn left from the curb, suddenly and without looking backward, directly in front of a motor vehicle driver who was overtaking in the same direction.

BICYCLIST TRAPPED BY SIGNAL: One collision (1.4%) occurred when a traffic signal changed before a bicyclist completed crossing an intersection.

Given the public paranoia about overtaking-type collisions, and the scale of the engineering investments proposed or committed to their prevention, the 5 collisions involving motorists passing too closely deserve extra attention. Here are the details of these collisions:

One overtaking collision occurred on a two-lane section of Davis Drive where a raised concrete median was installed. The pavement width between the raised concrete median and the drop to the soft shoulder is 11 feet. The travel lane striped within this space is 10 feet wide. (I made these measurements myself.) The driver of a motor vehicle towing a trailer sounded his horn at the bicyclist in the travel lane, and then attempted to squeeze past between the median and the bicyclist. The bicyclist slipped off the pavement as the tow vehicle squeezed past, then lost control on the soft shoulder/pavement edge and collided with the trailer as the driver moved to the right before the trailer had cleared the bicyclist.

One overtaking collision occurred on a rural two-lane section of Carpenter Upchurch Road. The travel lanes in this section are striped 10 feet wide with two-foot paved shoulders. The total asphalt width is 24 feet. The driver of a motor vehicle towing a trailer attempted to pass on a right curve. The driver moved back to the right side of the roadway before the trailer had cleared the bicyclist. The trailer collided with the bicyclist.

One overtaking collision occurred on a four-lane section of Kildaire Farm Road just south of W. Cornwall Road. The rightmost travel lane here is 11 feet wide. The driver of a van attempted to pass the bicyclist in the same narrow lane. The mirror of the van struck the bicyclist. The van left the scene without stopping.

One overtaking collision occurred on S. Walker street, a two-lane 25 mph road that is 25 feet wide. The police report shows that the 10-year-old bicyclist was in the center of the roadway when the collision occured. Given the unusual location of the collision, the slow travel speed of the motorist, and the young age of the cyclist, it is possible that the cyclist made a movement that contributed to the collision, i.e. turning left into a driveway. More investigation is needed to determine the cause of the collision.

One overtaking collision occurred on westbound Walnut Street just before the intersection with US/1 and Buck Jones Road. I have not yet measured the travel lane width at this location. The overtaking motorist "tapped the back tire" of the bicyclist shortly before making a right turn onto Buck Jones Road. More investigation is needed to determine the cause of the collision or contributing factors.

Note that there is a high volume of cycling activity in Cary. I believe that this amounts to over one million miles per year of bicycle travel on Cary roadways. According to a transportation consultant who worked on the town's comprehensive transportation plan, about 80% of cycling transportation miles in Cary are traveled by "avid" road cyclists who operate on roadways in the correct direction of travel for vehicular traffic. The vast majority of "non-avid" cycling transprotation miles are also traveled in the correct direction for vehicular traffic and most also occur on the roadway.

Given that wrong-way bicycle travel represents a very small percentage of the total number of bicycling miles, but represents about one half of the collisions, I believe that this breakdown of collisions illustrates the very high danger of wrong-way bicycle travel. Anyone traveling contra-flow on a vehicle, especially one capable of greater than walking speed, should be very cautious before moving in front of cross-street and driveway traffic. Operators of such vehicles should attempt to travel with the ordinary flow of vehicle traffic whenever possible. In general, the safest way to operate a vehicle in an urban area is according to the rules that apply to drivers of vehicles. Such operation maximizes one's visibility and predictability to other road users.

Regards,
Steven Goodridge
North Carolina Coalition for Bicycle Driving
https://humantransport.org/bicycledriving/

WRONG WAY: 36 collisions (49%) involved bicyclists traveling on the left half of the highway against the ordinary flow of vehicular traffic. Nearly all of these bicyclists were operating on the sidewalk prior to the collision. 30 of these wrong-way bicyclists were struck by automobile drivers who were turning right onto the roadway from a stop sign, red light, or driveway. These drivers were probably looking to the left prior to the collision.

RIGHT HOOK: 5 collisions (6.8%) involved motor vehicle drivers who were traveling in the same direction as the bicyclist when the motor vehicle drivers turned right and collided with the bicyclist. Four of these bicyclists were operating on the roadway; one was operating on the sidewalk prior to the collision. One of the bicyclists on the roadway was attempting to overtake the automobile driver on the right. One of the motor vehicle drivers attempted to turn right from the left through lane immediately after passing the bicyclist who was using the right through lane.

DRIVE OUT (PROPER DIRECTION CYCLIST): 5 collisions (6.8%) involved motor vehicle drivers who drove out across the roadway where the cyclist (who was operating in the correct direction for vehicular traffic on that side of the highway) had the legal right of way. Four of these bicyclists were operating on the roadway; one might have been on the sidewalk but the police report does not specify.

Below are excerpts from official and professional sources that warn against mandating or encouraging sidewalk bicycle operation.

"Sidewalks are generally inappropriate for use by adults because they put the adult bicyclist in conflict with motorists using driveways, and with pedestrians, utility poles and signposts. Also, the cyclist is generally not visible or noticed by the motorist so that the cyclist suddenly emerges at intersections, surprising the motorist and creating a hazardous condition."

"From the late 1970s through the mid-1980s a number of communities signed some sidewalks or built new paths for bicyclists parallel to roadways. Several states even passed laws forcing bicyclists to use such facilities if they existed. Bicycle/car crashes increased dramatically in some corridors, especially at driveways, intersections, on bridges, and other locations. Sidewalk or paths parallel to a roadway force bicyclists to ride against traffic half of the time. In either direction, motorists are often surprised by the presence of cyclists [on sidepaths], since [motorists] are neither conditioned nor capable of searching these locations for traffic moving at 8-15 mph. Many pedestrians were also hurt, or complained that it was no longer comfortable to walk. Also, many motorists became less considerate of bicyclists who continued to use the often safer roadway sections.…in no case should a bicyclist be forced to use the sidewalk pathway. Never sign a sidewalk or parallel path as a bikeway, since many motorists who see these signs will assume that those bicyclists riding on the roadway section are not permitted to be there."

"In residential areas, sidewalk riding by young children is common. With lower bicycle speeds and lower cross street auto speeds, potential conflicts are somewhat lessened, but still exist. Nevertheless, this type of sidewalk bicycle use is accepted..." [p. 20]
"...Sidewalks are typically designed for pedestrian speeds and maneuverability and are not safe for higher speed bicycle use. Conflicts are common between pedestrians traveling at low speeds (exiting stores, parked cars, etc.) and bicyclists, as are conflicts with fixed objects (e.g., parking meters, utility poles, sign posts, bus benches, trees, fire hydrants, mail boxes, etc.) Walkers, joggers, skateboarders and roller skaters can, and often do, change their speed and direction almost instantaneously, leaving bicyclists insufficient reaction time to avoid collisions."
"Similarly, pedestrians often have difficulty predicting the direction an oncoming bicyclist will take. At intersections, motorists are often not looking for bicyclists (who are traveling at higher speeds than pedestrians) entering the crosswalk area, particularly when motorists are making a turn. Sight distance is often impaired..." [p.58]

Sidewalk or sidewalk-type bike paths immediately adjacent to streets and highways will not be approved by ODOT for the following reasons:

• Bicyclists using a bike path may mistakenly believe that they have the right of way at intersections and driveways, and cross without looking.
• Stopped or parked motor vehicles at driveways often block the path.
• Physical barriers placed between motor vehicle lanes and immediately adjacent bicycle paths are a hazard to bicyclists and motorists and also complicate maintenance of the bicycle paths.
• Bicyclists legitimately using a roadway near a path may be subjected to harassment by motorists who mistakenly believe that bicyclists are required to use the path.
• If the adjacent bicycle path also serves as a pedestrian sidewalk, bicyclists may pose a hazard to pedestrians.
• Curb cuts are inconsistently available; bicyclists jumping sidewalk curbs risk losing control.
• Wide curb-lanes, bike routes, or barrier-free bike lanes are generally the best way to accommodate bicycle traffic along highway corridors.

"It is frequently assumed that a separated parallel pathway along an arterial street or highway will provide a superior facility for bicyclists than the provision of on-street accommodations. While a parallel path may be aesthetically appealing, and may serve pedestrians well, the use of sidewalks or parallel separated paths for bicycle accommodation creates the following problems:"

• These paths will operate as sidewalks, and will be used in both directions, despite signing to the contrary. Bicyclists coming from the right will not be noticed by drivers emerging from or entering cross streets and driveways. See Figure 13 for diagrams that show these potential conflicts.
• Travel in the direction opposite the flow of traffic is particularly hazardous during hours of darkness, because bicyclists may be blinded by oncoming motor vehicle headlamps.
• At intersections, drivers will not be looking for bicyclists, who will be traveling much faster than pedestrians, to enter the crosswalk area.
• At approaches to intersections, parked vehicles interfere with the visibility of bicyclists to road users. Also, at driveways sight distances on sidewalks and sidepaths are often impaired by buildings, property fences, vegetation, and other obstructions.
• Stopped cross street motor vehicle traffic or vehicles exiting side streets or driveways may block the sidepath or sidewalk.
• These paths are typically not safe for higher-speed use. Due to the speed differential, conflicts between bicyclists and pedestrians are common. Fixed objects such as parking meters, utility poles, sign posts, bus shelters and benches, trees, hydrants, and cross-sloped sidewalk ramps also pose a hazard to bicyclists.
• The development of extremely wide sidewalk or sidepaths does not necessarily add to the safety of bicycle travel, as wide sidewalks and paths will encourage higher speed bicycle use, magnifying the potential for conflicts at intersections and driveways, and conflicts with pedestrians and fixed objects.
• Many bicyclists will use the roadway instead of the sidewalk or sidepath because they have found the highway to be safer, more convenient, or better maintained. Bicyclists using the roadway are often subjected to harassment by motorists, who feel that in all cases bicyclists should be on the sidepath or sidewalk instead.
• There is the potential on sidewalks for bicyclists to accidentally ride off the curb, possibly causing a fall or collision with traffic on the roadway. While pathways may reduce the possibility of such collisions by using the recommended 1.5 m (5 ft) separation between the path and the roadway, such pathways will still be vulnerable to most of the other problems listed here.
• Experience has shown that the use of STOP or YIELD signs on sidewalks and pathways to reduce conflicts at driveways and cross streets has little or no benefit. Bicyclists will not comply with unreasonable restrictions on their right of way, especially if the adjacent roadway has no such limitations. This may also breed disrespect for other traffic control devices that are far more important for traffic safety.

Side paths

Also known as sidewalk bike paths, these facilities run along the sides of roads like sidewalks. Often they are sidewalks transformed into bike paths with “Bike Route” signs. As bicycle transportation facilities, side paths seldom allow bicyclists as much freedom of movement as the roadway. Frequently, side paths create more safety problems than they solve. Studies both in the U.S. and abroad have revealed high bicycle-motor vehicle accident rates on sidewalk bike paths, some as much as three times higher than the accident rates for on-street facilities, such as bike lanes (Clarke & Tracy, 1995, p. 85; Williams & McLaughlin, 1992, p. 7). A study in Palo Alto, California, found that, although streets with side paths carried only 15 percent of the city’s bicycle travel, those same streets hosted “70 percent of the reported bicycle/motor vehicle accidents on the bikeway system” (Zehnpfenning, Cromer, & Maclennan, 1993, p. 32). The State of Oregon Bicycle Master Plan summarizes some of the problems:

Sidewalks are generally unsafe because they put the cyclist in conflict with motorists using driveways and with pedestrians, utility poles and sign posts. Also, the cyclist is generally not visible or noticed by the motorist so that the cyclist suddenly emerges at intersections, surprising the motorist and creating a hazardous condition. Every attempt should be made to allow bicyclists to function as vehicle drivers, rather than as pedestrians (Oregon Department of Transportation, 1988, p. 24).

... the slow driver forces other drivers to ... take unnecessary risks while trying to pass.

Faster-moving vehicles can crash into the slower vehicle before they can slow down.

No person shall drive a vehicle at a speed greater than is reasonable and prudent under the conditions and having regard to the actual and potential hazards then existing. Consistent with the foregoing, every person shall drive at a safe and appropriate speed when ... special hazards exist with respect to pedestrians or other traffic ...

My conclusion from reading these stats is that sidewalk bicycling is less hazardous than bicycling on a roadway. Crossing roads is another matter, and bicyclists who ride on the crosswalk must be extra cautious (I understand that in some areas this is illegal, but here it is not). . .