Each one of the 723 on-scene, in-depth accident investigation cases was completely reconstructed and evaluated in order to determine the collision avoidance actions of the motorcycle rider and the other vehicle driver. Table 7.4.1 shows the evasive actions taken by the accident-involved motorcyclists.
In an accident-involved motorcycle, it was expected that this type of analysis would show collision avoidance problems that could be related to detection, decision or reaction failures. The most frequent collision avoidance actions taken were rear braking and swerving.
Table 7.4.1: Evasive action performed by rider
Motorcycle rider Evasive action taken
Frequency Percent
No evasive action 339 36.7
Use of horn 16 1.7
Flashing headlamp high beams 4 0.4
Rear braking 215 23.3
Front braking 116 12.6
Lane change 1 0.1
Swerve around hazard or obstacle 191 20.7 Lay-down, low side and slide 3 0.3
Jump or bail out 5 0.5
Braking, unknown which wheel(s) 32 3.5
Other 1 0.1
Unknown 1 0.1
Table 7.4.1 also shows that over one-third (37%) of the accident-involved motorcycle riders did not take any evasive action. There can be a variety of reasons that no evasive action was taken. One is that the accident occurs so fast that the rider has no time to take action. Alternatively, the rider may fail to detect a problem, or he may detect a problem too late to take any action, or he may decide to take no action. Some examples are as follows:
1. A rider stopped in traffic is rear-ended by an OV.
2. Another collision occurs immediately in front of the rider, shoving a vehicle into the motorcycle’s path.
3. The motorcycle rider fails to notice oil spilled on a rain-slick roadway. 4. An OV runs a red light at an intersection, striking the motorcycle.
Buildings obstruct the rider’s view of the hazard until less than one second before impact.
5. A car coming from the opposite direction turns right slowly across the rider’s path. The rider honks his horn and expects the other vehicle to stop, but it continues, striking the right side of the motorcycle.
6. A drunk rider runs off a right-hand curve without any apparent evasive action.
7. A rider changes lanes into the path of a faster-moving OV approaching from the rear.
Based on our analysis of each accident case, detection failures were the most frequent cause for a lack of evasive action. In some cases the rider failed to detect a plainly visible hazard (example 7 above), while in other cases (examples 3 & 4 above) it was impossible to detect the hazard. Decision failures (example 5) and reaction failures (example 6) were found to occur less frequently. There were 117 cases (31%) similar to examples 1 & 2 in which the riders took no collision avoidance action because of inadequate time. In other cases, a combination of decision and detection or reaction failures occurred. For example, if a rider decided to run a red light and failed to take evasive action before being struck by an OV, the decision to run the red light was coded as a decision failure, while the failure to see the other vehicle approaching from the left or right side was coded as a detection failure.
Reaction failures were usually coded for situations similar to example 6 above where the rider took no action before running off the road.
In Table 7.4.2, failures are listed as “strategic” or “impairment.” “Impairment” failures were coded when the rider had been drinking, while “strategic” failures were coded for accident situations where no alcohol or drugs
were involved. “Other” was usually coded when a rider had no chance to take any evasive action.
Table 7.4.2: Reason motorcycle rider took no collision avoidance action
Reason for no MC evasive action Frequency Percent Strategic detection failure 110 25.5 Impairment detection failure 108 25.1 Strategic decision failure 48 11.1 Impairment decision failure 45 10.4 Strategic reaction failure 14 3.2 Impairment reaction failure 38 8.8
Other 64 14.8
Unknown 4 0.9
Total 431 100.0
Evasive action evaluation
If the rider does take evasive action, his choice of evasive action may be correct or incorrect, and his execution of the evasive action may be correct or incorrect.
In this study, the standard of “correct” was set very high. One could call an evasive action the correct choice if it was an “appropriate” response to the situation, or one could say that the “correct” choice is the “best” response to the situation. For example, if a car pulls out of a driveway into the path of a motorcycle, rear-only braking could be considered an “appropriate” evasive response, but it was not considered the “best” response, as front-and-rear b r a k i n g m o s t o f t e n w o u l d b e . In a similar manner, “proper execution” was coded “yes” only if the rider showed highly skilled execution of whatever avoidance maneuver he or she chose. In other words, the rider could choose the wrong evasive action (such as swerving left when a swerve to the right would have been better), but if the rider executed the evasive action skillfully it would be coded as “proper execution.” Also, if the rider executed the proper evasive action but waited too long before beginning evasive action, this was coded as improper action. An example would be a rider (or car driver) who saw a collision threat ahead, honked his horn and finally braked skillfully but too late to avoid a collision.
Of course, there were cases in which the rider took evasive action but so little time was available that no evasive action could possibly avoid a collision. Table 7.4.3 shows a cross-tabulation of the 379 cases in which both proper choice and proper execution of the evasive action were evaluated. Only one- third of riders who took evasive action (19% of the 723 cases) made the proper choice. About 39% of those who took evasive action (20% of the 723 cases) executed their chosen evasive action properly. Only 12% of those who took
evasive action (6% of the 723 cases) chose the proper evasive action and executed it properly.
Table 7.4.3: Rider evasive action, proper choice by proper execution
Proper execution
No Yes Total
Proper choice
Frequency % Frequency % Frequency %
No 143 38 102 27 245 65
Yes 88 23 46 12 134 35
Total 231 61 148 39 379 100
The reason that each collision avoidance maneuver failed to prevent a collision was examined and the results are reported in Table 7.4.4.
Table 7.4.4: Reason collision avoidance did not prevent collision
Reason collision avoidance failed Frequency Percent
Decision failure 148 38.7
Reaction failure 50 13.1
Inadequate time available 117 30.6
Loss of control 54 14.1
Other 12 3.1
Unknown 1 0.3
Total 382 100.0
Evasive actions and time available for action
The most common reasons for unsuccessful avoidance were inadequate time and decision failures. In addition, most riders took no evasive action at all. In order to explore the relationship between time and avoidance failure in more detail, a cross-tabulation of the time from PE to impact compared to the type of avoidance failure was generated. The analysis shows that different failures clustered in different time distributions.
Two- thirds of the accidents (231 of 341) in which the rider took no evasive action fell in to the 0 - 2.0 second range of times from PE to impact. By comparison, the largest group of decision failures (88 of 148, or 60%) fell into the 1.0 - 3.0 time range (Table 7.4.5). Two-thirds of the accidents involving reaction failures (34 of 50) had times from PE to impact of 1.6 - 3.5 seconds. Over 80% of crashes that were coded "inadequate time to avoid" fell into the 0.5 - 2.5 second range. Finally, most crashes due to slide-out loss of control ranged 1.0 -
Table 7.4.5: Evasive actions and time available for action
Reason motorcycle evasive action did not succeed Time from PE to impact (seconds) No evasive action Decision failure Reaction failure Inadequate time Loss of control 0.1- 1.0 111 11 2 19 5 1.1 – 1.5 68 28 3 36 9 1.6 – 2.0 52 26 9 30 8 2.1 – 2.5 27 18 7 13 5 2.6 – 3.0 28 16 11 5 9 3.1 – 3.5 13 8 7 2 1 3.6 – 4.0 10 13 2 4 2 > 4.0 5 16 5 5 2 Loss of control
About 20% of the accidents involved some form of motorcycle loss of control (Table 7.4.6). Sometimes the loss of control was the accident, other times the rider lost control while trying to avoid a collision.
Slide-outs and high-sides represented 40% of the loss of control situations identified in this study. They were usually due to errors of braking, most often skidding the rear wheel while trying to swerve. However, at least one case involved dangerously slippery pavement, with an oil spill on rain-wet asphalt. Over-braking of the front brakes typically caused the front wheel to lock up and this resulted in extremely fast fall to the pavement.
“Capsize” was defined as simply falling over the pavement. It usually occurred when the rider was too drunk and unable to control the motorcycle. There were also cases in which the rider fell asleep while riding and capsized. The motorcycle capsized in about 3.7% of all cases.
Running wide on a turn or running off the roadway accounted for over one- third of the loss of control accidents. It was commonly associated with alcohol. In fact, half of those cases in which an alcohol-involved rider lost control, it was by running off the road, compared to only 14% of non-drinkers who lost control. (Table 7.4.7).
The typical outcome of going off the road was a collision with some part of the environment, i.e. post, curb, trees, etc. Occasionally a motorcycle “ran off the road” by drifting into the other vehicle path and collide with an oncoming vehicle. The many fixed objects along the roadside – poles, trees, mailboxes, phone booths, planters, etc., were found to stop a tumbling rider immediately and cause severe injury.
Table 7.4.6: Motorcycle loss of control mode
Motorcycle rider Loss of control mode
Frequency Percent No loss of control 581 80.4 Capsize/ fall over 27 3.7 Braking slide-out, low-side 53 7.3 Braking slide-out, high-side 4 0.6 Cornering slide-out high-side 1 0.1 Ran wide on turn, ran off road 51 7.1
Lost wheelie 1 0.1
End-over, reverse wheelie 1 0.1
Continuation 1 0.1
Other 1 0.1
Unknown 2 0.3
Total 723 100.0
Table 7.4.7: Alcohol impairment and loss of control mode
Alcohol impairment Loss of control mode No
alcohol No Yes Unknown Total No loss of control 373 30 175 3 581 Capsize, fall over 14 2 11 0 27 Braking slide-out, low-side 29 5 19 0 53 Braking slide-out, high-side 3 0 1 0 4 Cornering slide-out high-side 0 0 1 0 1
Ran wide on turn 8 0 41 2 51
Loss wheelie 1 0 0 0 1
End-over, reverse wheelie 0 0 1 0 1
Continuation 0 0 1 0 1
Other 1 0 0 0 1
Unknown 1 0 1 0 2
Total 430 37 251 5 723
Rider position on motorcycle just before impact
All but four riders were in the normal riding position. In one case a rider was lying on the seat with both feet extended to the rear of the motorcycle just before impact (Table 7.4.8). In two cases the riders attempted to “jump or bail out” from the imminent collision. Occasionally, riders commented that they lifted their leg to avoid the impact with the other vehicle, but there was no clear documentation to support this comment.
Table 7.4.8: Riding position on motorcycle
Riding position at time of crash Frequency Percent Normal seating position 719 99.4 Dismounting, jumping to side 2 0.3 Abnormal seating position 1 0.1
Other 1 0.1
Total 723 100.0
Passenger position on motorcycle just before impact
The majority of the accident-involved passengers (95%) were in the normal riding position behind the motorcycle rider at the time of the collision. In three cases the passenger was seated in front of the rider. There were 13 cases in which the passenger was riding with both legs on the left side of the motorcycle and one case in which the passenger was riding with both legs on the right side of the motorcycle. In cases that the motorcycle held more than 1 passenger, the second passengers were either in front of the rider (3 cases) or behind the first passenger (8 cases) as shown in Table 7.4.9.
Table 7.4.9: Passenger riding position on motorcycle
Passenger position at time of crash Frequency Percent Immediately behind motorcycle rider 226 95.4 Immediately in front of motorcycle rider 3 1.3 Behind passenger in location number 1 8 3.4
Total 237 100.0
Calculated time from precipitating event (PE) to impact
The time available to the motorcycle rider for collision avoidance usually begins with the initiation of the PE and terminates with the impact.
Table 7.4.10 shows the distribution of the time from the precipitating event to impact for all 723 on-scene, in-depth accident investigation cases. The median time was found to be 1.9 seconds and the mean value was 2.1 seconds. As shown in Table 7.4.4, about 30% of failed collision avoidance was simply due to a lack of time for successful evasive action.
The very short times from PE to impact (i.e., less than 1 second) often occurred when the rider ran off the road, failing to make a last-second steering input that might have avoided running off the road.
Table 7.4.10: Time from precipitating event to impact
Time (sec) Frequency Percent
0 - 0.5 71 9.8 0.6 – 1.0 79 10.9 1.1 – 1.5 148 20.5 1.6 – 2.0 126 17.4 2.1 – 2.5 71 9.8 2.6 – 3.0 69 9.5 3.1 – 3.5 31 4.3 3.6 – 4.0 32 4.4 4.1 – 4.5 22 3.0 4.6 – 5.0 5 0.7 > 5.0 7 1.0 Unknown 62 8.6 Total 723 100.0
Collision contact on the motorcycle
In about 30% of cases, the collision contact was located at the center front of the motorcycle, which includes the front tyre and wheel, fender and forks (Table 7.4.11). Another 22% and 19% first collision contacts were at the left and right front of the accident-involved motorcycle. When these three configurations are collapsed, a total of about 70% of the motorcycle collision contacts were predominately frontal impact.
Table 7.4.11: Motorcycle first collision contact
First collision contact on MC Frequency Percent
Center front 208 28.8 Center rear 18 2.5 Left center 71 9.8 Left front 160 22.1 Left rear 15 2.1 Right center 62 8.6 Right front 140 19.4 Right rear 25 3.5 Top center 1 0.1 Top front 7 1.0 Undercarriage center 5 0.7 Undercarriage front 4 0.6 Undercarriage right 2 0.3 Unknown 5 0.7 Total 723 100.0
Figure 7.4.1 shows the distribution of first collision contacts for the 723 on- scene, in-depth accident investigation cases.