Traffic records for all bicyclist fatalities occurring in Arizona during the year 2009 were categorized and listed according to manner of collision and assignment of fault. Primary results are that 11 of 25 fatalities (44%) were determined to be the fault of the cyclist; while 14 of 25 (56%) were the fault of a motor vehicle driver. The most common manner of collision is when a driver strikes a cyclist from behind.
The full report is available in pdf format:
Manner and Fault in Bicyclist Traffic Fatalities: Arizona 2009
Supporting data: 2009CyclistFatals.xls
Comments or questions may be left here, or contact me.
There were some somewhat out-of-context statements about my report on the npr.org health blog. They probably should have mentioned that the report covers only FATAL bike-MV collisions (a tiny fraction of all bike-MV collisions), and that the manner of collision in fatals varies significantly from non-fatals.
City of Mesa has various crash analysis reports available. For example in the 2007 Bicycle crash analysis found that of the 231 bike-vehicle crashes, the cyclist was most at fault in 57% (131 crashes), and the driver in 43% (100 crashes).
The percentage of fault attributed to cyclists is very likely to be overstated because in many of the cyclist most at fault cases, the reason was suspicious; e.g. in 40 cases the cyclist was most at fault for “Other”, while only 8 drivers were faulted for “Other”. Faults such as Other, Unknown, and Inattention (when used as primary or the only fault) are prone to be used in cases where the investigator has for unstated reasons (bias?) decided one party is guilty, but are violating no laws. The report tries to explain the high-other as follows:
“Other violation. A review of PARs seemd to indicate that this was a catch-all classification. If there appeared to be a question as to which operator was at fault, this violation was identified and attributed to the pedalcyclist 17.3% of the time”
Previous analysis found an even higher suspicious use of “Other” fault. In 2005, the report found cyclists most at fault 68% of the time. Unsurprisingly, there were an outsized number of “Other” faults against the cyclist; 60, versus only 10 for drivers.
It should be pointed out that the concept of most at fault prior to the 8th Edition (October 2008) of the Crash Manual was considered preferred, but not mandatory to code Traffic Unit #1 as most at fault. (see here for links to both the 7th and 8th editions), nonetheless the City of Mesa report use Unit #1 to claim to establish fault. So perhaps there is a disconnect between the police (who do the investigations) and the traffic analysis people who crunch the numbers. And also, since the number of other is going down over time, perhaps the police are taking the investigations more seriously, which is a positive sign.
This conference paper may be of interest: Schramm, Amy J. and Rakotonirainy, Andry and Haworth, Narelle L. (2008) How much does disregard of road rules contribute to bicycle-vehicle collisions? full text .pdf.
“The analysis would suggest that it is usually driver behaviour that contributes to bicycle vehicle collisions, with the motor vehicle being the at fault unit in nearly two thirds of reported crashes. This trend is even more noticeable in bicycle-vehicle collisions where the cyclist is of driving age. Traffic violations were reported in over two thirds of bicycle-vehicle collisions. In crashes where traffic violations were found to have occurred, vehicles were more likely to have broken the road rules. This is in contrast to the popularly held opinion that cyclists’ failure to adhere to road rules results in crashes”
This published paper examined 6774 bicycle crashes occurring in Queensland, Austrailia and found “cyclists were deemed to be at fault in 44.4% of the incidents”. Coincidentally, 44% is the percentage of cyclists at fault in 2009 fatal collisions in Arizona.
And when only bicyclist-MV crashes were considered, “The analyses reported here showed that the motor vehicle was at fault in 65.6% of bicycle motor vehicle crashes with traffic violations recorded against 85.4% of these drivers. This contrasts sharply with the media articles and surveys portraying cyclists as risk-takers who disobey traffic regulations.” I wonder if the 65.6 figure is a type-o, because in the body of the paper in the section on bicycle-MV crashes it says “The bicyclist was deemed the at-fault vehicle in 2809 instances (44.4%)” which would seem to me to leave 55.6% drivers at fault, and not 65.6.
Schramm, Amy J. and Rakotonirainy, Andry and Haworth, Narelle L. (2010)
The role of traffic violations in police-reported bicycle crashes in Queensland. Journal of the Australasian College of Road Safety, 21(3). pp. 61-67.