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Publication Number: FHWA-HRT-10-024
Date: April 2010

Development of a Speeding-Related Crash Typology

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RESULTS FOR SINGLE-VARIABLE ANALYSES

 

The following sections describe the results of the single–variable analyses for the set of variables selected in the GES, FARS, North Carolina, and Ohio databases. For each variable, tables containing data from these four databases (and two definitions for the State data) are presented first, followed by a brief description of findings. It is noted that even though GES and FARS data are presented in the same table (with the State data in separate tables), the percentages of SR crashes within a given category should not be compared across databases. For example, FARS category percentages are likely to be higher than the same GES category percentages since, in general, the FARS data have a higher percentage of SR crashes (30 percent versus 20 percent).

 

TYPES OF CRASHES MOST LIKELY DUE TO SPEEDING

Type of Collision

First Harmful Event

Nonmotorist Involvement

 

TYPES OF CRASHES MOST LIKELY DUE TO SPEEDING

In this section, tables are presented to examine the types of crashes that are most likely a result of speeding as well as the basic nature of SR crashes. The tables show the percentage of SR crashes by type of collision, first harmful event, and nonmotorist involvement.

Type of Collision

Table 7. Frequency and number/percentage of SR crashes regarding type of collision.

Type of Collision FARS GES
All Crashes SR Crashes All Crashes SR Crashes
n n Percent n n Percent
Collision with motor vehicle Rear–end 2,253 927 41.15 1,730,195 603,805 34.90
Head–on 3,959 655 16.54 116,689 13,456 11.53
Angle       1,681,286 97,530  
Front–to–side, same direction 484 131 27.07      
Front–to–side, opposite direction 2,243 611 27.24      
Front–to–side, right angle 5,024 828 16.48      
Front–to–side, unknown direction 289 33 11.42      
Sideswipe, same direction 473 141 29.81 350,816 23,243 6.63
Sideswipe, opposite direction 469 85 18.12 58,714 9,278 15.80
Rear–to–side 88 45 51.14      
Rear–to–rear 6 3 50.00 3,788 686 18.11
Other 75 18 24.00      
Total 15,363 3,477 22.63 3,941,488 747,998 18.98
No collision with motor vehicle 22,048 8,063 36.57 1,762,624 447,073 25.36
Unknown 176 13 7.39 8,626 499 5.78
Total 37,587 11,553 30.74 5,712,738 1,195,570 20.93
Note: n represents frequency of crashes. Blank cells indicate that the code was not present in this database.

 

Table 8. Frequency and number/percentage of SR crashes regarding type of collision in North Carolina.

Type of Collision FARS GES
All Crashes SR Crashes All Crashes SR Crashes
n n Percent n n Percent
Collision with motor vehicle Rear–end 2,253 927 41.15 1,730,195 603,805 34.90
Head–on 3,959 655 16.54 116,689 13,456 11.53
Angle       1,681,286 97,530  
Front–to–side, same direction 484 131 27.07      
Front–to–side, opposite direction 2,243 611 27.24      
Front–to–side, right angle 5,024 828 16.48      
Front–to–side, unknown direction 289 33 11.42      
Sideswipe, same direction 473 141 29.81 350,816 23,243 6.63
Sideswipe, opposite direction 469 85 18.12 58,714 9,278 15.80
Rear–to–side 88 45 51.14      
Rear–to–rear 6 3 50.00 3,788 686 18.11
Other 75 18 24.00      
Total 15,363 3,477 22.63 3,941,488 747,998 18.98
No collision with motor vehicle 22,048 8,063 36.57 1,762,624 447,073 25.36
Unknown 176 13 7.39 8,626 499 5.78
Total 37,587 11,553 30.74 5,712,738 1,195,570 20.93
Note: n represents frequency of crashes.

 

Table 9. Frequency and number/percentage of SR crashes regarding type of collision in Ohio.

Type of Collision Over Speed Limit Too Fast for Conditions Total SR Not SR Total
n Percent n Percent n Percent n Percent n Percent
Collision with motor vehicle Rear–end 1,236 0.90 4,530 3.29 5,766 4.19 131,817 95.81 137,583 100.00
Head–on 205 2.88 714 10.03 919 12.91 6,202 87.09 7,121 100.00
Backing up 10 0.11 70 0.80 80 0.91 8,668 99.09 8,748 100.00
Angle 626 0.66 6,725 7.11 7,351 7.77 87,299 92.23 94,650 100.00
Sideswipe, same direction 453 1.43 3,573 11.27 4,026 12.70 27,675 87.30 31,701 100.00
Sideswipe, opposite direction 208 3.83 344 6.33 552 10.16 4,882 89.84 5,434 100.00
Left turn                    
Right turn                    
Other                    
Total 2,738 0.96 15,956 5.59 18,694 6.55 266,543 93.45 285,237 100.00
No collision with motor vehicle 9,410 6.45 21,885 14.99 31,295 21.44 114,654 78.56 145,949 100.00
Unknown 8 0.05 1,909 11.33 1,917 11.37 14,938 88.63 16,855 100.00
Total 12,156 2.71 39,750 8.87 51,906 11.59 396,135 88.41 448,041 100.00
Note: n represents frequency of crashes. Blank cells indicate that the code was not present in this database

As can be seen, regardless of the database or the definition used, SR crashes are primarily single–vehicle crashes. The only exception is in the over speed limit definition used in Ohio where sideswipe same direction crashes had a higher SR percentage but a much lower frequency. This finding would infer multilane highways. The databases differed with respect to which vehicle–to–vehicle crashes were most likely to be SR. GES and FARS data indicated rear–end crashes, while the State data indicated both types of sideswipe and head–on crashes.

 

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First Harmful Event

Table 10. Frequency and number/percentage of SR crashes regarding first harmful events.

First Harmful Event FARS GES
All Crashes SR Crashes All Crashes SR Crashes
n n Percent n n Percent
Rollover/overturn 4,243 1,772 41.76 134,466 58,419 43.45
Jackknife 10 4 40.00 6,317 1,996 31.60
Other noncollision 529 117 22.12 51,431 3,091 6.01
Collision with nonmotorist 4,375 376 8.59 104,323 2,569 2.46
Collision with motor vehicle 15,458 3,490 22.58 4,170,075 776,635 18.62
Collision with animal 172 19 11.05 270,053 1,461 0.54
Collision with other nonfixed objects 363 66 18.18 44,868 5,259 11.72
Collision with ground, ditch, culvert, embankment or boulder 4,114 1,893 46.01 190,667 70,848 37.16
Collision with building, fence, wall, etc. 658 324 49.24 121,563 42,527 34.98
Collision with bush or tree 3,210 1,559 48.57 142,500 63,633 44.65
Collision with other fixed objects 4,399 1,932 43.92 470,975 166,728 35.40
Unknown 56 1 1.79 5,502 2,402 43.66
Total 37,587 11,553 30.74 5,712,740 1,195,568 20.93
Note: n represents frequency of crashes.

 

Table 11. Frequency and number/percentage of SR crashes regarding first harmful events in North Carolina.

First Harmful Event Over Speed Limit Too Fast for Conditions Total SR Not SR Total
n Percent n Percent n Percent n Percent n Percent
Rollover/
overturn
1,055 11.36 3,933 42.37 4,988 53.73 4,295 46.27 9,283 100.00
Jackknife 12 2.86 150 35.71 162 38.57 258 61.43 420 100.00
Other noncollision 87 2.10 343 8.29 430 10.39 3,709 89.61 4,139 100.00
Collision with nonmotorist 30 1.13 35 1.31 65 2.44 2,598 97.56 2,663 100.00
Collision with motor vehicle 3,466 1.34 9,572 3.70 13,038 5.04 245,603 94.96 258,641 100.00
Collision with animal 44 0.13 23 0.07 67 0.19 34,905 99.81 34,972 100.00
Collision with other nonfixed objects 69 1.25 259 4.71 328 5.96 5,172 94.04 5,500 100.00
Ran off road 1,901 8.84 7,254 33.73 9,155 42.57 12,350 57.43 21,505 100.00
Collision with other fixed objects 6,130 8.93 28,359 41.30 34,489 50.22 34,182 49.78 68,671 100.00
Not coded 8 1.89 16 3.78 24 5.67 399 94.33 423 100.00
Total 12,802 3.15 49,944 12.29 62,746 15.45 343,471 84.55 406,217 100.00
Note: n represents frequency of crashes.

 

Table 12. Frequency and number/percentage of SR crashes regarding first harmful events in Ohio.

First Harmful Event Over Speed Limit Too Fast for Conditions Total SR Not SR Total
n Percent n Percent n Percent n Percent n Percent
Rollover/
overturn
127 10.03 257 20.30 384 30.33 882 69.67 1,266 100.00
Jackknife                    
Other noncollision 1,451 10.99 893 6.77 2,344 17.76 10,855 82.24 13,199 100.00
Collision with nonmotorist 263 4.76 22 0.40 285 5.16 5,237 94.84 5,522 100.00
Collision with motor vehicle 15,642 5.48 3,063 1.07 18,705 6.55 266,834 93.45 285,539 100.00
Collision with animal 2,738 5.49 17 0.03 2,755 5.52 47,151 94.48 49,906 100.00
Collision with other nonfixed objects 562 11.21 129 2.57 691 13.78 4,323 86.22 5,014 100.00
Ran off road                    
Collision with other fixed objects 8,301 11.73 16,524 23.36 24,825 35.09 45,915 64.91 70,740 100.00
Not coded 1,593 9.45 324 1.92 1,917 11.37 14,938 88.63 16,855 100.00
Total 30,677 6.85 21,229 4.74 51,906 11.59 396,135 88.41 448,041 100.00
Note: n represents frequency of crashes. Blank cells indicate that the code was not present in this database.

Reinforcing the findings from table 7 through table 9, table 10 through table 12 show that regardless of database or definition, there was a consistent pattern indicating higher SR percentages and frequencies for various types of single–vehicle, off–roadway crashes. The SR percentage was much lower for vehicle–to–vehicle crashes and even lower for collisions with nonmotorists, which will be further examined in the next section.

 

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Nonmotorist Involvement

Table 13. Frequency and number/percentage of SR crashes regarding nonmotorist involvement.

Nonmotorist Involvement FARS GES
All Crashes SR Crashes All Crashes SR Crashes
n n Percent n n Percent
No pedestrians/bicycles 32,937 11,065 33.59 5,605,824 1,192,053 21.26
1+ pedestrians/bicycles 4,646 486 10.46      
Pedestrian accident       59,483 3,084 5.18
Bicycle accident       47,255 388 0.82
Wheelchair involved       177 45 25.42
Total 37,583 11,551 30.73 5,712,739 1,195,570 20.93
Note: n represents frequency of crashes. Blank cells indicate that the code was not present in this database.

 

Table 14. Frequency and number/percentage of SR crashes regarding nonmotorist involvement in North Carolina.

Nonmotorist Involvement Over Speed Limit Too Fast for Conditions Total SR Not SR Total
n Percent n Percent n Percent n Percent n Percent
No pedestrians/
bicycles
12,761 3.17 49,860 12.37 62,621 15.53 340,492 84.47 403,113 100.00
1+ pedestrians/
bicycles
41 1.32 84 2.71 125 4.03 2,979 95.97 3,104 100.00
Total 12,802 3.15 49,944 12.29 62,746 15.45 343,471 84.55 406,217 100.00
Note: n represents frequency of crashes.

 

Table 15. Frequency and number/percentage of SR crashes regarding nonmotorist involvement in North Carolina.

Nonmotorist Involvement Over Speed Limit Too Fast for Conditions Total SR Not SR Total
n Percent n Percent n Percent n Percent n Percent
No pedestrians/
bicycles
30,549 6.88 21,205 4.78 51,754 11.66 392,027 88.34 443,781 100.00
1+ pedestrians/
bicycles
128 3.00 24 0.56 152 3.57 4,108 96.43 4,260 100.00
Total 30,677 6.85 21,229 4.74 51,906 11.59 396,135 88.41 448,041 100.00
Note: n represents frequency of crashes.

All databases and definitions of SR crashes indicated that the pedestrian and bicycle crashes were less likely to be SR than other types of crashes. The no pedestrians/bicycles crashes had two to five times the SR percentage. Note that in table 13, the GES and FARS data were probably more meaningful since the State–based findings were more rural; they did not include urban streets where many of the pedestrian and bicycle crashes would occur.

 

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FHWA-HRT-10-024

 

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