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  G = Gainesville

  A = Austin

  SB=Santa Barbara

A Tale of Three Cities

 

Analysis of Bicycle-Motor Vehicle Crashes

Wayne Pein

All police-reported bicycle-motor vehicle crashes occurring in Gainesville, Florida (158 cases), Austin, Texas (173 cases), and Santa Barbara, California (77 cases) during the calendar year 1995 were classified according to a slight modification of a typology developed in the early 1980's by the National Highway Traffic Safety Administration (NHTSA). NHTSA’s coding scheme, which is based on seminal work in crash analysis by Cross and Fisher, relies on the police report to identify 45 possible bicycle-motor vehicle crash types.

A number of variables such as bicyclist age, bicyclist roadway position and direction, roadway factors, and temporal and environmental attributes were also ascertained from the police report. These variables are essential to understanding the nature of the crashes so that appropriate countermeasures can be implemented.

Results.

Table 1 shows in rank order the most prevalent bicycle-motor vehicle collisions in each city. The listed crashes comprise 85% of all the cases in Gainesville, and 82% of both Austin and Santa Barbara crashes. Four crash types that are common to all three communities are color coded to more easily demonstrate their relative ranking (there are other crash types common to all three cities but they are not among the top 10 in rank), and reveal similarities and differences in crash patterns between the cities.

Rank

Gainesville, Florida


Austin, Texas


Santa Barbara, California


1

Drive Out At Stop Sign

(n=39; 24.7%)


Drive Out At Stop Sign

(n=27; 15.6%)


Bicyclist Strikes Parked Vehicle (n=12; 16%)


2

Right Turn On Red

(n=23; 14.6%)


Ride Out At Intersection

(n=24; 13.9%)


Motorist Right Turn

(n=12; 16%)


3

Drive Out At Midblock

(n=20; 12.7%)


Ride Out At Midblock

(n=20; 11.6%)


Drive Out at Midblock

(n=10; 13%)


4

Ride Out At Intersection

(n=17; 10.8%)


Motorist Left Turn- Facing Bicyclist (n=15; 8.7%)


Drive Out At Stop Sign

(n=7; 9%)


5

Motorist Left Turn- Facing Bicyclist (n=11; 7.0%)


Drive Out At Midblock

(n=12; 6.9%)


Motorist Overtaking

(n=6; 8%)


6

Motorist Right Turn

(n=10; 6.3%)


Right Turn On Red

(n=12; 6.9%)


Ride Out At Intersection

(n=5; 6%)


7

Ride Out At Midblock

(n=8; 5.1%)


Bicyclist Left Turn In Front

Of Motorist (n=10; 5.8%)


Motorist Left Turn- Facing Bicyclist (n=4; 5%)


8

Drive Through

(n=7; 4.4%)


Assault

(n=7; 4.0%)


Bicyclist Lost Control

(n=4; 5%)


9


Motorist Left Turn-Bicyclist Same Direction (n=7; 4.0%)


Drive Out From On-Street Parking (n=3; 4%)


10


Motorist Overtaking

(n=7; 4.0%)


Weird

(n=3; 4%)


n=135; 85.4% of 158 total


n=141; 81.5% of 173 total


n=63; 81.8% of 77 total



The 15 different crash types represented in Table 1 are described and listed below in approximate descending average (among the three communities) rank order of occurrence. The top five collisions are accompanied by a diagram depicting bicyclist and motorist positions.

  1. "Drive Out At Stop Sign." The crash occurred at an intersection at which the motorist was facing a stop sign. The bicyclist was on a crossing path.
  2. Fig1S.gif (7777 bytes)

  3. "Drive Out At Midblock." The motorist was entering the roadway from an uncontrolled driveway or alley. The bicyclist was on a crossing path.
  4. Fig2S.gif (7417 bytes)

  5. "Ride Out At Intersection." The crash occurred at an intersection at which the bicyclist was facing a stop sign, red traffic signal, or failed to yield at an uncontrolled intersection. The motorist was on a crossing path.
  6. Fig3S.gif (7278 bytes)

  7. "Motorist Left Turn—Facing Bicyclist." The motorist made a left turn at an intersection or into a driveway while facing the approaching bicyclist.
  8. Fig4S.gif (5259 bytes)

  9. "Motorist Right Turn." The motorist and bicyclist were on parallel paths in the same direction, and the motorist was making a right turn at a roadway intersection or a driveway.
  10. Fig5S.gif (4596 bytes)

    -- note no images for the following, which compose very small percentages of the accidents reported--

  11. "Right Turn On Red." The crash occurred at an intersection at which the motorist was facing a red traffic signal and was attempting a right turn on red. The bicyclist was on a crossing path (typically coming off the sidewalk facing traffic).
  12. "Ride Out At Midblock." The bicyclist was entering the roadway from an uncontrolled driveway or alley or a shoulder/curb position. The motorist was on a crossing path.
  13. "Motorist Overtaking." The motorist was overtaking the bicyclist. No turning movements were involved. The motorist misjudged the passing space, stated that the bicyclist was undetected, or the event could not be clearly specified.
  14. "Bicyclist Strikes Parked Vehicle." The bicyclist struck a motor vehicle parked within the roadway right-of-way. The bicyclist may have struck the driver’s extended side door or the back of the motor vehicle.
  15. "Bicyclist Left Turn In Front Of Motorist." The bicyclist made a left turn or swerve in front of an overtaking motor vehicle.
  16. "Drive Through." The motorist was facing a red traffic signal and drove over the crosswalk before or after stopping (but not making a right turn on red), or ran the signal. The bicyclist was on a crossing path.
  17. "Drive Out From On-Street Parking." The motorist was exiting (or entering) on-street parking and the bicyclist was riding along the roadway.
  18. "Assault." The motorist intentionally struck the bicyclist.
  19. "Motorist Left Turn—Bicyclist Same Direction." The motorist made a left turn at an intersection or into a driveway and the bicyclist was riding in the same direction (typically facing traffic).
  20. "Weird." Unusual circumstances.

Discussion.

Comparing cities.

The three most frequent collisions in Gainesville comprising 82 (51.9%) crashes involve the motorist facing either a traffic control device or merging from a midblock location and the bicyclist on a crossing path. Of these bicyclists, 65 (79.3%) were riding on the sidewalk facing traffic. Four bicyclists were riding facing traffic while in the street. The driver may have failed to yield or failed to stop prior to crossing a stop line or sidewalk.

The three most frequent collisions in Austin also involve bicyclist and motorist on a crossing path. Here, however, the second and third ranked collisions, "Ride Out At Intersection" and "Ride Out At Midblock" are characterized by the bicyclist violating basic yielding requirements. Moreover, at "Drive Out At Stop Sign" there were six bicyclists riding facing traffic while in the street, another violation of traffic law (seven were riding facing traffic on the sidewalk).

Seven "Assault" incidents, the eighth ranking collision in Austin, is extraordinarily high. Only one "Assault" was noted in Gainesville, and none was found in Santa Barbara.

In Santa Barbara, the top two collisions have the parties initially on parallel rather than crossing paths as is the case in Gainesville and Austin. Together, the five most frequent collisions in Santa Barbara involve primarily driver merging or turning actions. In some cases bicyclist action/position is a contributing or proximal cause. The number one crash in Santa Barbara (tied with "Motorist Right Turn"), "Bicyclist Strikes Parked Vehicle," occurred only once in Austin and did not happen in Gainesville. All twelve of these events were the bicyclist striking/being struck by an open(ing) motor vehicle driver door.

Differences in crash patterns between cities are likely in part explained by bicyclist age differences, sidewalk riding, and size of roads. These three factors are examined below. The amount of on-street parking on arterial roadways is an obvious variable, and the extent of community educational efforts also likely plays a significant role.

Age variation. Child bicyclists tend to be involved in different types of crashes as compared to older bicyclists. Children are more likely to be implicated in crashes in which they disregarded basic yielding requirements, such as when exiting a driveway. Figure 6 depicts the age distribution of involved bicyclists in the three cities.

Fig6S.gif (4752 bytes)

Bicyclists ages 0-14 comprised 27.1% of victims in Austin, 14.8% in Gainesville, and 10.4% in Santa Barbara. The 0-14 age range accounted for 16 of 20 (80%) "Ride Out At Midblock" and 12 of 24 (50%) "Ride Out At Intersection" crashes in Austin, the second and third ranked collisions in that city.

Sidewalk Riding. Bicyclists were riding along the roadway (in contrast to crossing the roadway at a midblock location or being non-roadway related) in Gainesville 92% of the time, in Austin 88% of the time, and in Santa Barbara 96%. Of these, the specific location and directional distributions are shown in Figure 7.

Fig7S.gif (4878 bytes)

Gainesville had substantially more total sidewalk riding among crash involved bicyclists than the other cities, particularly sidewalk riding facing the normal flow of traffic. This is at least partial explanation for the appreciable percentage of "Drive Out At Stop Sign," "Right Turn On Red," and "Drive Out At Midblock" type crashes, the three most prevalent collisions in this city. These crash types are more likely to occur as a result of riding on the sidewalk.

Size of road. The collision occurred on a multi-lane road (comprising more than two lanes) in 72% of the cases in Gainesville, 59% in Austin, and in 47% of the Santa Barbara crashes. It is possible that bicyclists in Gainesville are more likely to ride on sidewalks because of the large size and attendant complexity and voluminous motor traffic of that city’s roads.

Examining the aggregate.

The collisions that occurred in the three cities are characteristic of crash types found in urbanized areas, where intersections, driveways, sidewalks, and conflicting movements with motor vehicles are abundant. The top three ranking crashes occur when the parties are on crossing paths. The fourth, "Motorist Left Turn—Facing Bicyclist," and fifth, "Motorist Right Turn," ranking crashes involve the participants on a parallel path and a driver turning movement. Both of these were over-represented on multi-lane roads. "Motorist Left Turn—Facing Bicyclist" crashes were over-represented under conditions of darkness, and were especially relevant to unlighted bicyclists. "Motorist Right Turn" included situations in which the motorist had overtaken the bicyclist, or the bicyclist was in the process of overtaking the motorist on the right.

Conclusions/Recommendations

In broad generalities, bicycle crashes in Gainesville are characterized by a large proportion of sidewalk riding, particularly facing traffic; Austin by a relatively noteworthy amount of bicyclist violations and driver hostility, with a higher percentage of young riders; and Santa Barbara by appreciable on-street parking related episodes.

Due to the inherent conflicts at driveways and intersections, bicyclists should ride in the street and not on the sidewalk. Any riding on the sidewalk should be at a slow speed. Education and enforcement directed to reducing wrong way and sidewalk riding, is advisable. Since it is likely that sidewalk riding will be an ongoing issue, and in many cases tolerated if not encouraged, sidewalk design where bicyclists are expected should attempt to mitigate the negative consequences of sidewalk riding. Effort should also be put forth to better ensure motorist compliance with stopping at a stop limit line and prior to crossing over sidewalks or sidewalk crosswalk areas, whether marked or implied. It may be advisable to formally mark "implied" crosswalk areas.

Because of their small size, position near the right edge of the road, and relative infrequency, bicyclists are not as readily noticeable to motorists as are motor vehicles. Bicyclists should be wary of on-coming motorists turning left in front of them and pulling out of driveways and side streets. Again, an education/awareness campaign could be directed at both bicyclists and motorists. At locations where high conflict rates exist, the sites should be examined taking into account both the motorist and the bicyclist task, and appropriate countermeasure(s) implemented.

Drivers exiting their vehicles from on-street parking should be more aware of the presence of bicyclists. This can be addressed through an awareness campaign and/or "Watch For Bicyclists" signs place with on-street parking. Bicyclists should learn, again through an education effort, and/or be channelized through pavement markings, to ride beyond open door range from parked motor vehicles.

The process of crash "typing" with analysis of precipitating actions, predisposing factors and contributing circumstances is a valuable tool for those interested in reducing a community’s bicycle-motor vehicle collisions. Different communities may exhibit varied patterns of crashes. By knowing in what types of crashes bicyclists are principally involved and under what context, appropriate engineering, educational, and enforcement countermeasures can be targeted.


Biography.

Wayne Pein formerly was a Research Associate at the University of North Carolina Highway Safety Research Center. He has been involved in a number of Federal Highway Administration and state level bicycle and pedestrian research projects.

 

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08/16/11
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