Manner and Fault in Bicyclist Traffic Fatalities: Arizona 2009

Most at Fault driver / bicyclists collisions Arizona 2009Abstract

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.

Full Report

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 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.

Background References

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.

23 thoughts on “Manner and Fault in Bicyclist Traffic Fatalities: Arizona 2009”

  1. I would like to respond to any/all criticisms or questions…
    Here is one from a thread at

    > P.S. And while data collection on this is poor, there are some strong
    > indications that a large percentage of the “hit from behind” cyclists
    > are riding in the dark without lights or reflectors.

    I think the data, poor though it may be, shows that is not at all the case:

    There were 10 hit-from-behind cases.
    Only 4 were in darkness. I tend to believe that all of these victims were meeting their lighting requirement/duty (to have a rear reflector or light). In at least two of the cases the police specifically said to the media words to the effect of “the bicyclist was doing everything right”, or something.
    By the way; all four were hit-and-run drivers.
    Additionally, three of the four generated indictments for manslaughter (and IIRC all 3 resulted in conviction of either manslaughter or neg hom); I am told authoritatively that to prove any homicide charge here the prosecution must show the collision was the fault of the defendant, and not simply that the defendant was DUI.
    The fourth driver ended up getting convicted of “simple” leaving-the-scene.
    Other anecdotal evidence is that several (3 by my count) were somewhat hard-core roadies doing night training during our (Phoenix) hot weather months, and not, say, homeless transients just out rolling around. (I don’t say that to sound cold. every life is sacred; but all things being equal some groups of cyclists are more likely than others to have a reflector or light).

    The other 6 were in the light. One was listed as dawn and that guy specifically had a reflector (and large/slow vehicle triangle). the dusk victim’s driver complained of sun glare.

  2. This paper has a rather long title —
    White Papers for: “Toward Zero Deaths: A National Strategy on Highway Safety” —White Paper No. 5— Safer Vulnerable Road Users: Pedestrians, Bicyclists, Motorcyclists, and Older Users

    It is intersting to see if their cited data aligns with the 25 fatals studied in Arizona; for example, helmet usage “the IIHS bicycle fact sheet indicates that 91 percent of the bicyclists killed in 2008 reportedly were not wearing helmets”. In the Arizona sample, 24% were wearing helmets, and 40% were known to be not wearing one. The rest were unknown.

    Another example was darkness — “The Florida study of fatal crashes showed approximately 60 percent of the fatal bicyclist crashes occurring in non-daylight conditions, and that more than 45 percent of the bicycles involved in nighttime crashes had no lighting (Spainhour et al, 2005).”
    In the Arizona data 52% were non-daylight, and I am working on trying to find a number for nighttime w/no lighting

  3. While the sample is too small to draw conclusions, “hit from behind at night” is consistent with the NHTSA claim that alcohol is involved in 38% of cyclist fatalities involving collision with a motor vehicle. Certainly these were not simply DUI, but it remains the gorilla in the background.

  4. As a bicyclist, I am not surprised to hear that the majority of car/bike collisions are caused by drivers. Both motorists and bike riders need to pay attention and obey the laws so we can reduce the number of collisions and fatalities.

  5. news piece from refers to the ADOT BSAP, and also Flagstaff local data regarding fault:

    “Those findings are consistent with a local study done by the city of Flagstaff, which found 97 percent of accidents happened on sunny days — the time when most cyclists are out.
    The local study also found a nearly even split between cyclists and motorists in who caused the accident, with motorists being at fault slightly more often

  6. See also, Annotations for 28-701.

    Apparently the Campbell v. English quote is no longer good case law:

    Butane Corp v Kirby, 66 Ariz 272. 1947.
    We now hold that the driver of an automobile at night is not required under all circumstances to see any object in the road in front of him which comes within the radius of his lights and be able under all circumstances to stop his car before striking the object.

    Various cases are referenced in their analysis:
    141 Wisconcin 57: Lauson v Town of Fond du Lac
    141 Washington 399: Morehouse v City of Everett
    64 Arizona 101: Alabam Freight Lines v Phoenix Bakery

    Here’s an alternative (although I don’t know if it’s still in effect):

    Slavin v City of Tucson 17 Arizona Appeals 16, 1972
    Existence of speed limits does not authorize travelers on
    street to blithely drive at maximum speed limit without regard
    to actual and potential hazards existing along the roadway.

    It references ARS 28-701D, which is worth rereading.

    Here’s some more:

    State of AZ v Livingston. 206 Ariz 145 (App) – 2003:
    Defendant’s isolated and minor crossing of a shoulder line of highway
    did not amount to conduct prohibited by statute, and thus police
    officer lacked reasonable basis to stop defendant’s automobile;
    statutory language demonstrated express legislative intent to avoid
    penalizing brief, momentary, and minor deviations outside marked
    lines. ARS 28-729.

    Notably, the “statutory language demonstrating express legislative
    intent” is the word “practicable”.

    Pearson & Dickerson V Harrington.
    60 Ariz 361. 1943.
    “… no one has the rigt to act as though he were the only
    person thereon or entitled to be thereon”
    The highway are, of course, established and maintained at
    public expense for the use and benefit, for lawful purposes,
    of all the citizens, and it cannot be claimed that the drivers
    of automobiles have any special right or privilege in the use
    or enjoyment thereof.

    On Mon, Oct 04, 2010 at 12:33:50PM -0700, Justin T Pryzby wrote:
    > Quoted from the “701 annotes” I sent you:
    > “The driving of an automobile at such a speed that motorist cannot
    > stop his automobile within range of his vision is negligence as a
    > matter of law.” Campbell v. English (1941) 56 Ariz. 549, 110 P.2d
    > 219.

  7. It seems like these sorts of papers are really just shenanigans with statistics (Multinomial Logit!?) and don’t really tell me anything i don’t already know; so, e.g., higher speed roads are more likely to have more severe bicyclist injuries.

    I was interested to see where the data came from: it was from a 5 year data set of all bicyclist crashes in Florida’s state-highway system.
    (in fact i think even the same five years as the study done for ADOT’s BSAP which was probably not a coincidence; probably had something to do with funding amonst the states)


    Likelihood Parameterization of Bicycle Crash Injury Severities
    or full .pdf paper

    Deo Chimba, Daniel Emaasit, Boniphace Kutela
    Department of Civil Engineering, Tennessee State University, Nashville, USA
    Received March 23, 2012; revised May 3, 2012; accepted May 25, 2012

    This paper evaluates different factors and parameters contributing to likelihood of bicycle crash injury severity levels. Multinomial Logit (MNL) model was used to analyze impact of different roadway features, traffic characteristics and environmental conditions associated with bicycle crash injury severities. The multinomial model was used due to its flexibility in quantifying the effect of the independent variables for each injury severity categories.

  8. More about overtaking again…
    In Arizona 2009 there were
    10/25 = 40% motorist overtaking cyclist fatalities

    I didn’t try and look at all 2010 fatals in any comprehensive way, however, commencing in 2010 NHTSA (the “FARS” data) does a detailed breakdown of *all* us ped or bike fatals —
    in 2010 in Arizona there were
    3/19 = 20%

    as you can see the number, because it’s relatively small/rare to begin with, and particularly in a small state like AZ, is going to jump around a lot.


    switching over to the whole US:
    in 2010 the number according to FARS is 154/618 = 25%

    which if anything is somewhat less than was found in two well-respected older studies
    FHWA-RD-95-163 “Pedestrian and Bicycle Crash Types of the Early 1990’s”
    and the 1977 “Cross and Fisher” which found about 30 and 40%

    The state of North Carolina typed all their collisions for 5 years (2003-2007) and their magic number was 41%

    And always remember, the mechanism for fatals is not representative of overall bike-mv collisions. It’s easy to over-emphasize motorist-overtaking collisions. E.g. to take the extreme example: you can eliminate the risk of motorist-overtaking collision altogether by riding counter-flow on the sidewalk.

  9. I’ve often wondered about cyclist-ped statistics. They are not tracked by FARS (because no motor vehicle is involved); according to this blurb, the CDC puts out something. That’s a pretty stark ratio — 1,000 to 1 peds killed in automobile collisions compared to bicycle collision… (though off the top of my head, 63 over 10 years sounds low)…

    “Some 4,834 cyclists and 59,925 pedestrians were killed by motor vehicles in the United States between 1999 and 2009 (the most recent year for which figures are available), according to the Centers for Disease Control and Prevention. Cyclists killed just 63 pedestrians, or about six a year, during the same time period. Although this type of incident is rare, it has led to calls from campaign groups to better protect pedestrians from cyclists”

  10. here is a query to select fatal hitandruns from 2009, so there were 5:

    | incidentid | incidentdate |
    |    2290764 | 2009-05-29   |
    |    2295567 | 2009-07-11   |
    |    2296189 | 2009-06-08   |
    |    2306432 | 2009-09-09   |
    |    2306437 | 2009-08-08   |

    I thought (and reported) that there were 6, but asdm only shows 5. The “missing” one is 8/15/2009 Russell Jenkins (victim) / Gary Foshee. I don’t have the police report, but according to news reports, MSCO said the driver fled. “The driver fled the scene, but the Maricopa County Sheriff’s Office Traffic Unit later arrested Gary Foshe”.
    So I’m not quite sure whats up with that, I mean why it wouldn’t have been coded a hit and run in asdm.

    So just out of curiosity, looking at 2010 — asdm says only 1 fatal hitandrun (of 19 total fatals)

    | incidentid | incidentdate |
    |    2384711 | 2010-03-19   |

    But there was another 11/14/2010. I have the ACR, and it is marked as hit/run unit #1 (the box is right in the center near top on page 1, by the way). The was another 7/10/2010 but for reasons i don’t necessarily agree with, motorized bicyclists are coded as a DRIVER, and not as pedalcyclist.

    2011 has 5 listed (of 23 total bicyclist fatalities) in asdm:

    | incidentid | incidentdate |
    |    2509596 | 2011-01-13   |
    |    2553828 | 2011-05-16   |
    |    2589356 | 2011-09-04   |
    |    2578108 | 2011-09-24   |
    |    2585201 | 2011-10-25   |

    mysql> SELECT incidentid,incidentdate FROM 2009_incident i WHERE EXISTS (SELECT 1 FROM 2009_unit u WHERE u.IncidentID=i.IncidentID AND u.eUnitType IN (‘PEDALCYCLIST’)) AND HitAndRunFlag=1 AND InjurySeverity=5;

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