[Warning/correction not yet made: in the table below where it says MV-only, that’s not quite correct, it’s really incidents where no pedalscylists are involved. The MV-only calculations should also exclude pedestrians; this can be accomplished by saying u.eUnitType LIKE ‘PED%’ In the query below i corrected it but didn’t correct the table; the percentages don’t really change since there are relatively few ped crashes ]
Here is a breakdown of Collision Manner, and rates, for MV collisions (i.e. one or more MV, and not involving a ped or bicyclists) compared to bike-MV collisions.
The megatrends are that rear end collisions are, by far, the predominant manner of collision for MVonly crashes; wheres for bike-MV crashes this manner is quite infrequent — almost twelve times more frequent. For bike-MV crashes, the predominant manner is angle, i.e. so called “turning and crossing” movements (although left turn is broken out as a separate manner).
The 38% rate of REAR END crashes for MVs actually understates the rate — if you back out the number of SINGLE VEHICLE crashes; you see that nearly half of all multi-car collisions are REAR END(!). 38,499/(101,055 – 18,647) = 47%. Inattention? Does this mean that motorists actually are more attentive to same-direction traffic when it’s a bicyclist, compared to another motorist? hmmm.
+------------------------------+-------+--------+------+--------+-------------+ | eCollisionManner | MVonly| MVrate |bikeMV|bikerate|MV:bike ratio| +------------------------------+-------+--------+------+--------+-------------+ | REAR_TO_REAR | 287 | 0.0028 | NULL | NULL | NULL | | UNKNOWN_99 | 859 | 0.0085 | 40 | 0.0189 | 0.44973545 | | REAR_TO_SIDE | 895 | 0.0089 | 11 | 0.0052 | 1.71153846 | | SIDESWIPE_OPPOSITE_DIRECTION | 1244 | 0.0123 | 46 | 0.0217 | 0.56682028 | | HEAD_ON | 1438 | 0.0142 | 45 | 0.0212 | 0.66981132 | | OTHER_97 | 3160 | 0.0313 | 404 | 0.1905 | 0.16430446 | | SIDESWIPE_SAME_DIRECTION | 10727 | 0.1062 | 124 | 0.0585 | 1.81538462 | | LEFT_TURN | 11888 | 0.1176 | 189 | 0.0891 | 1.31986532 | | ANGLE_FRONT_TO_SIDE | 13411 | 0.1327 | 1194 | 0.5629 | 0.23574347 | | SINGLE_VEHICLE | 18647 | 0.1845 | NULL | NULL | NULL | | REAR_END | 38499 | 0.3810 | 68 | 0.0321 | 11.86915888 | +------------------------------+-------+--------+------+--------+-------------+ total num of MVonly crashes = 101,055. total num of bike-MV crashes = 2,121 source: 2012 ASDM
It seems like it would be useful to plug in injury severity; and check for consistency with previous data, e.g. Cross and Fisher; to see relative injury rates — e.g. we might expect to see rear end for bicyclists (which are low frequency) result in high relative rates of injury.
ALL 18 fatalities in 2012 were OTHER (as were all 23 2011 fatalities); whereas in 2009, and 2010 there was what you might expect a variety of manners. It seems to suggest strongly that someone somewhere is making a concerted effort to mask this data.(?? why?). A spot-check of 3 fatal ACRs I have for 2011 and 2012 show they all have ANGLE. Somebody is diddling with the data. In any event; this field has no useful information in it anymore with respect to fatalities.
[sidenote on PEDESTRIAN. The same queries can be run with PEDESTRIAN in place of PEDALCYCLIST. There is some sort of scrubbing going on there as well. In 2012 all 130 ped fatals were OTHER except for one HEAD_ON. In 2011 all 146 were OTHER. Older data is more mixed, but curiously 2010 is more mixed than 2009 was. Also if you look at fatal incidents, without regard to whether it was MVonly, MV-ped, or MV-bike, you see a broad mix of CollisionManner; and that the OTHER is comprised mostly of fatal peds + bicyclists. Incidentally, the SINGLE_VEHICLE category is by far the largest when looking at all fatal incidents, at 316 is like 1/3 of the total]
Some clouds in the data
[note: data fiddling / fudgery on manner of collision lands here at #clouds. That refers to the habit of crash reports to get somehow and inexplicably (by whom? by ADOT? no one will say) to summarily override the manner of collision from, say, a rear-end to OTHER. This particular field, nearly without exception, gets overridden for bicyclist and ped fatalities. MESSING AROUND WITH THE DATA MAKES IT MORE DIFFICULT TO ANALYZE]
The crash manual (see adot-traffic-collision-database “reference document” p.37) has some confusing/contradictory verbiage associated with this. It is Block 17 on the ACR form; the “MANNER OF CRASH IMPACT- Identifies the manner in which two motor vehicles in transport initially came together”. Strictly speaking, there is no possible correct answer as to any bike-MV (or ped-MV) crash; since those crashes are not two motor vehicle. It appears that at least most crash reports treat a bike, for the purposes of this block anyway, as one motor vehicle in transport.
I had a brief email exchange with Tom Bragan @dot.gov over the equivalent field in the mmucc (actually now C9 in the 4th ed) , where pretty much the same confusion/contradiction exists. He said he would take that under consideration for the next rev of their documentation (the 5th edition). By the way, the mmucc definitions, compared to AZ, lack a SINGLE VEHICLE, and LEFT TURN (which is simply a subset of ANGLE).
It seems like the best thing to do to clear up the discrepancy is to simply expand the definition to “two motor vehicles in transport, or at least one motor vehicle in transport and one other traffic unit in transport”. And adjust each manner’s definition accordingly.
Make the big table to compare MV(only) manners and rates to MV-bike manners and rates:
SELECT 0 INTO @b; SELECT 0 INTO @a; SELECT a.eCollisionManner, @a, a.c, a.r, @b, b.c, b.r, a.r/b.r, b.r/a.r FROM (SELECT eCollisionManner, count(1) c, @a, count(1)/@a r FROM (SELECT *, @a:=1+@a FROM 2012_incident i WHERE NOT EXISTS (SELECT 1 FROM 2012_unit u WHERE i.IncidentID=u.IncidentID AND u.eUnitType LIKE 'PED%')) x GROUP BY 1) a LEFT OUTER JOIN (SELECT eCollisionManner, count(1) c, @b, count(1)/@b r FROM (SELECT *, @b:=1+@b FROM 2012_incident i WHERE EXISTS (SELECT 1 FROM 2012_unit u WHERE i.IncidentID=u.IncidentID AND u.eUnitType='PEDALCYCLIST')) y GROUP BY 1) b ON a.eCollisionManner=b.eCollisionManner GROUP BY a.eCollisionManner ORDER BY 3; ### Note: the clause LIKE 'PED%' will exclude both pedalcyclists and pedestrians
Select by manner; differentiate by UnitNumber and InjurySeverity:
SELECT eCollisionManner,count(1) FROM 2012_incident i WHERE EXISTS (SELECT 1 FROM 2012_unit u WHERE u.IncidentID=i.IncidentID AND u.eUnitType IN ('PEDALCYCLIST') AND u.UnitNumber IN (1,2) ) AND InjurySeverity IN (1,2,3,4,5) GROUP BY 1 ORDER BY 1 ASC;