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"Crossing" your accident statistics, title graphic (4.7 kB GIF)

by John Williams, RSCM


This article first appeared in the journal Bicycle Forum
(#8, 1982, p. 22) and is republished here by permission
of the author, editor (and illustrator...), John Williams.

It's been four years since we first received copies of A Study of Bicycle/Motor Vehicle Accidents: Problems and Countermeasure Approaches(1), otherwise known as the Cross/Fisher report. It might be putting it too dramatically to say this study transformed the bicycle field. Nevertheless, its impact has been substantial. Many education programs have been revamped to reflect some of the insights from the Cross/Fisher study; many new programs have been developed based squarely on its data. Pamphlets are coming out that discuss the "Cross Types" (the 36 different car/bike collision types identified in the report); filmmakers tout their wares as "based on the Cross Report."

In the facilities field, the effect is less clear. Some critics use the study to ask pointedly "which of these accident types will your facility designs take care of?" In general, few designers have closely considered the implications of the study. For example, one of the major "physical" problems that the study identified was the sight-distance restriction. Bushes, fences, parked cars, and other obstructions to the view of passing motorists figured significantly in several critical accident types (driveway rideouts, stop sign rideouts). Yet, few bike facility planners have taken this lesson to heart.

In a few progressive communities, police agencies have used the study as a basis for their work in identifying key violations to crack down upon. Most notably, stop sign violations, wrong-way riding, no-lights-at-night, and unexpected turns have been the subjects of attention.

Yet, one question remains -- even in those communities that have considered the insights of the Cross/Fisher study. Does the study accurately reflect local accident patterns; how much can we generalize?

While one of the strengths of the study was its careful analysis of accidents in four widely-separated communities (Denver, Los Angeles, Detroit, and Miami), we cannot be absolutely sure that our own communities will experience identical problems. Some specialists use this fact as reason enough to discard the study and all its implications. The responsible approach, however, is to look at local accident records to compare and contrast them with the study's findings.

In Missoula, we chose the latter alternative. With very little investment, the City was able to categorize two and one half years worth of bike/car collision reports into Cross/ Fisher's classes and types. The initial work was done by a University of Montana student, Mike Calhoun, in the Spring term, 1981. It is now being carried out by the Police Department as a normal function.

Methods

When Mike came to work for me in the Bicycle Program, I gave him a copy of the summary report Bicycle Safety Education: Facts & Issues(2), which does an admirable job of distilling the study into its basics. We also talked about accidents; I described how the Cross/Fisher study was conducted and something about the overall accident picture. I explained that, while police reports are important sources of information, they do not represent all bike accidents. They do, however, represent a good sample of the most serious accidents -- particularly those involving autos.

We then looked at some examples of reports and tried placing the collisions into the classes and types. Once Mike became familiar with the classification scheme, he had little trouble categorizing the crashes. (His biggest problem was reading the handwriting of some officers!)

We discussed just what information was needed from each report, coming up with a simple list (see figure 1) and he set to work. This phase of the project was the most time-consuming. He had to look up the reports for each accident for the past 2 1/2 years, decipher the information, decide which type of accident had occurred and fill out the form. (Older reports are kept in the basement, and aren't very accessible.) We decided to discard any report that didn't have a diagram showing the collision. Without such a picture, positive classification proved risky. In the end, Mike had classified 91 accidents.

Findings

Figure 2 shows the results and how they compared to Cross/Fisher's findings. While we can't be 100% certain of the statistical reliability of our small study, we do feel it gives a good indication of Missoula's accident problems.

One of the things that struck us most directly was the high median ages for all classes except Class A. Clearly, we have an older cyclist population than many communities, perhaps due to the presence of the University of Montana. It was also a surprise to see that our two biggest types were 9 and 23: motorist's unexpected left turn and motorist's failure to yield at a controlled intersection (stop sign).

The ages of cyclists (figure 3) seem reasonable when considered in light of the accident locations. Many of the collisions took place on major thoroughfares -- just where one might expect to find adult cyclists, particularly utility riders.

At this stage, it would be useful to look at exposure (i.e. how much bike traffic is on those streets) to determine whether the rate per bike/mile (or per bike/minute) is high. I expect that it isn't, but that we simply have a lot of bike traffic out on those routes. The bike counts we plan for next season will tell us more.

Other findings were interesting as well. Of our 19 night-time accidents, only one involved a cyclist with a light. That points to a significant problem in our town, which casual observation easily confirms!

We also found that, according to the police officers' assessments, about one third of the cyclists sustained 'incapacitating injuries.' There was one death. Thus, it seems that a cyclist who gets into a collision with a car is likely to get hurt.

Implications

Since the Missoula program has a strong safety component, we take these results seriously. First, while in the past, I've emphasized the wrong-way riding problem, in the future I'll give more attention to adult riders' difficulties at intersections. One approach will be to produce several TV public service announcements on left-turn conflicts and cross traffic dangers.

Teaching adult cyclists how to deal with traffic will get renewed attention. We've offered courses on Effective Cycling, but they've often gone unnoticed by cyclists. In the future, we'll have to work harder to bring people in. Motorist attitudes and behaviors will be difficult to influence but we will have to try, by making sure driver training focuses on specific bike/car conflicts and by getting the word out in the media.

Conclusion

Looking at our own accident picture in light of the Cross/Fisher study was a useful exercise. It allowed the Bicycle Program to better focus its efforts on actual problems. It also gave the Program credibility and exposure; newspapers, radio, and television are always more impressed if one can say "one third of the accidents were such and such" than if one can only say "I think there are a lot of such and such accidents but don't have any data."


Figure 1

Information taken from Police Desk Reports

DR#
Location
Date
Time of Day
Cyclist's Age
Type and Class of Accident (according to Cross Study)
Citation (if any) and to whom given
Sex of Cyclist
Injury (if any) and Type
Comments

Figure 2:

A comparison of the Missoula accident data
with the national Cross/Fisher Study

Accident
type
Missoula number Missoula percentage Cross/Fisher Study: (injuries/
fatalities)
Class A: Bicycle ride-out from driveway, alley and other midblock locations. Median age: 9.5 yrs.
Type 1: residential driveway ride-out 4 4.5% 5.7%/6.7%
Type 2: commercial driveway ride-out 2 2.2 3.2/2.4
Type 3: parallel direction driveway ride-out 0 0 2.5/2.4
Type 4: ride-out over shoulder or curb 2 2.2 2.5/3.6
Total Class A: 8 8.9% 13.9%/15.1%
Class B: Bicycle ride-out at controlled intersection.
Median age: 20 yrs.
Type 5: stop sign or yield sign 6 6. 7% 10.2%/7.8%
Type 6: signal phase change; cyclist caught in intersection 2 2.2 3.1/0.6
Type 7: ride-out at signal: multiple threat 1 1.1 2.0/2.4
Total Class B: 9 10% 17.0%/12.0%
Class C: Motorist turn/merge/drivethrough/driveout.
Median age: 19.5 yrs.
Type 8: Motorist driveout from commercial driveway/alley 4 4.4% 5.3%/0%
Type 9: Motorist failure to yield at stop or yield sign 13 14.4 10.2/1.2
Type 10: Motorist failure to yield at signal 3 3.3 1.9/0
Type 11: Motorist backing from driveway 0 0 0.8/0
Type 12: Motorist didn't even slow for sign or signal 1 1.2 0.5/1.2
Total Class C: 21 23.3% 18.7%/2.4%
Class D: Motorist overtaking/overtaking threat.
Median age: 21 yrs.
Type 13: Motorist overtaking, cyclist not seen 4 4.4% 4.0%/24.6%
Type 14: Motorist overtaking/out of control 2 2.2 0.7/4.2
Type 15: Motorist overtaking/counter active evasive action 1 1. 1 1.7/2.4
Type 16: Motorist overtaking/misjudged space required to pass 3 3.3 2.0/1.8
Type 17: Motorist overtaking/cyclist's path obstructed 1 1. 1 2.0/0.6
Type unknown: 1 1.1 0.1/4.2
Total class D: 12 13.3% 10.5%/37.8%
Class E: Bicyclist unexpected turn/swerve.
Median age: 14 yrs.
Type 18: Bicyclist unexpected left turn; parallel paths; same direction 1 1.1% 8.4%/8.4%
Type 19: Bicyclist unexpected left turn; parallel paths; opposite direction 5 5.6 3.2/3.0
Type 20: Bicyclist unexpected swerve left; parallel paths; same direction 0 0 1.5/3.6
Type 21: Wrong-way bicyclist turns right; parallel paths 2 2.2 1.1/1.2
Total Class E: 8 8.9% 14.2%/16.2
Class F: Motorist unexpected turn.
Median age: 21 yrs.
Type 22: Motorist unexpected left turn; parallel paths; same direction 2 2.2% 1.3%/0.6%
Type 23: Motorist unexpected left turn; parallel paths; opposite direction 13 14.5 7.6/0.0
Type 24: Motorist unexpected right turn; parallel paths 3 3.3 5.6/1.8
Total Class F: 18 20% 14.5%/2.4%
Class G: Other. Median age: 21 yrs.
Type 25: Vehicles collide at uncontrolled intersection; orthogonal paths 3 3.3% 2.8%/0.6
Type 26: Vehicles collide head on, wrong way bicyclist 2 2.2 3.6/2.4
Type 27: Bicyclist overtaking 3 3.3 0.9/0.6
Type 28: Head-on; wrong way motorist 0 0 0.8/1.8
Type 29: Parking lot 0 0 0.8/0.8
Type 30: Head-on; counteractive evasive action 0 0 0.1/0
Type 31: Bicyclist cuts corner when turning left 0 0 0/0.6
Type 32: Bicyclist swings wide when turning right 0 0 0.3/0
Type 33: Motorist cuts corner when turning left 0 0 0.4/0
Type 34: Motorist swings wide when turning right 0 0 0.1/0
Type 35: Motorist driveout from on-street parking 0 0 0.3/0
Type 36: Weird 6 6.8 0/7.2
Total Class G: 14 15.6% 11.2%/13.8%

Figure 3:
Missoula age categories compared to Cross/Fisher Study

Age of cyclist: # % age in category (Cross/Fisher Study: % ages for non-fatals)
less than 6 yrs. 1 1 % (2.0%)
6-11 12 14 (27.5)
12-15 13 15 (37.1)
16-19 16 18 (13.9)
20-29 35 40 (12.2)
30-44 10 11 (3.8)
45-59 0 0 (1.8)
60+ 0 0 (1 .7)

References

1. A Study of Bicycle/Motor Vehicle Accidents: Identification of Problem Types and Countermeasure approaches; Dr. Ken Cross and Gary Fisher; 3 volumes; the study from which the above reference was taken; 1977; may still be available from NTIS (Springfield, VA 22161); DOT HS 803 317; volumes one and two are very useful.

2. Bicycle Safety Education: Facts & Issues; Dr. Ken Cross; 1978; published by AAA Fdn for Traffic Safety; 8111 Gatehouse Rd, Falls Church, VA 22042; single copies available for $0.85.


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1982, Bicycle Forum
Last modified February 18, 2001