1. Week 8, CE 552 - Typical crash rates and distributions
- Crashes that take the highest toll on human life

2. Why analyze crash data? Identify patterns Determine causes
Develop countermeasures

3. Rates …why? To compare locations
To decide if a location is at abnormal risk
Rate per million entering vehicles:
In-class calculation

4. In-class calculation
This should really be RHMVM, shouldn’t it?

8. Expected value analysis
Use only to compare “similar” sites (geometry, control, volume)
Problem: crashes are non-neg. count data (normal distribution does not apply)
In-class calculation

9. Cluster analysis
E.g., if a site has one right-angle, two rear-end and 6 left-turn crashes, one might say the left-turn crashes represent a cluster
But … what if the # of left turns is very high … then, is 6 high?
Need exposure data
Must usually use good engineering judgment

10. Summarizing crash data
Type
Severity, e.g., KABCO, MAIS
Time Periods
Hour
Day
Month
Contributing
Circumstances
Environmental
Conditions
a) light condition
b) surface condition

11. Typical crash rates Iowa data for risk by road type
Oregon crash rates (compare to Iowa)
Source: NCHRP Web Only Document 126
Guidelines for using NC crash rates
Crash rate discussion

12. Aussie rates – compare road types

17. European crash rates by road type
Low traffic flow roads – there are significant differences in fatal and
serious accident rate between roads with less than 10,000 Average
Annual Daily Traffic (AADT), roads with 10,000 to 20,000 AADT, and
roads with more than 20,000 AADT. (The ratio of these differences is
about 2.3:1.8:1);
Note: to convert /bvkm to /HMVM, multiply by ~6 (Iowa K+A+B crash rate per HMVM in ~60, much lower than the numbers presented above for Europe if you multiply them by 6)

19. Kentucky Intersection Crash Rates

20. Massachusetts Intersection Crash Rates

21. From Oregon Study …

25. Crashes that take the highest toll on human life
Head-ons, Intersections, ROR, VRU
Show iRAP video

26. Head-on collisions
In this video, the ADAC Strassentest Car barely escapes a head-on crash.
Fatal Head On Accident Six Killed On US12 Near Morton WA
Truck crossing median – 7 fatals video

28. Intersections (junctions)
See: UMN captured crashes

29. Manner of collision

30. Run-off the road (ROR)

33. Vulnerable Road users Motorcycles, bikes, pedestrians
Bicyclists and Other Cyclists (DOT-HS )

34. Children