CE 635 Typical crash rates and distributions Crashes

CE 635 - Typical crash rates and distributions - Crashes that take the highest toll on human life

Rates …why? • To compare locations • To decide if a location is at abnormal risk • Rate per million entering vehicles: In-cl ass calc ulati on

In-cl ass This should really be RHMVM, shouldn’t it? calc ulati on

Expected value analysis • Use only to compare “similar” sites (geometry, control, volume) In-cl ass calc • Problem: crashes are non-neg. count data (normal distribution does not apply) ulati on

Cluster analysis • E. g. , if a site has one right-angle, two rear-end and 6 left-turn crashes, one might say the leftturn 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

High Crash Location Methods • • Frequency Rate Severity/Cost Some combination – Iowa DOT uses. 2 F+. 2 R+. 6 C • Critical Rate Factor method • Empirical Bayes

Critical Crash Rate Factor method Error: this should say Z, not S For derivation of equation and interpretation of terms, see link

Next step: engineering study at sites

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

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

Aussie rates – compare road types

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) http: //www. eurorap. org/library/pdfs/roaddesignfactors. pdf

Kentucky Intersection Crash Rates http: //www. ktc. uky. edu/Reports/KTC_03_21_SPR 258_03_2 I. pdf

Massachusetts Intersection Crash Rates

From Oregon Study … http: //www. oregon. gov/ODOT/HWY/TRAFFIC-ROADWAY/docs/pdf/safety_of_4 -leg_vs_T. pdf

http: //www. oregon. gov/ODOT/HWY/TRAFFIC-ROADWAY/docs/pdf/safety_of_4 -leg_vs_T. pdf

http: //www. oregon. gov/ODOT/HWY/TRAFFIC-ROADWAY/docs/pdf/safety_of_4 -leg_vs_T. pdf

http: //www. oregon. gov/ODOT/HWY/TRAFFIC-ROADWAY/docs/pdf/safety_of_4 -leg_vs_T. pdf

Crashes that take the highest toll on human life • Head-ons, Intersections, ROR, VRU • Show i. RAP video http: //www. eurorap. org/library/pdfs/roaddesignfactors. pdf

Head-on collisions • head-on crash. • Fatal Head On Accident Six Killed On US 12 Near Morton WA • Truck crossing median – 7 fatals video http: //onlinepubs. trb. org/onlinepubs/nchrp_rpt_500 v 20. pdf

Intersections (junctions) See: UMN captured crashes http: //onlinepubs. trb. org/Onlinepubs/nchrp_rpt_500 v 5. pdf

Manner of collision

Run-off the road (ROR) http: //www. t 2. unh. edu/nltapa/Pubs/fhwa's_roadway_departure_program. pdf http: //www. t 2. unh. edu/nltapa/Pubs/PLD-1. pdf

http: //onlinepubs. trb. org/Onlinep ubs/nchrp_rpt_500 v 6. pdf http: //www. t 2. unh. edu/nltapa/Pubs/fhwa's _roadway_departure_program. pdf

Vulnerable Road users Motorcycles, bikes, pedestrians • Bicyclists and Other Cyclists (DOT-HS-810 -986) • http: //onlinepubs. trb. org/Onlinepubs/nchrp_rpt_500 v 10. pdf • http: //onlinepubs. trb. org/onlinepubs/nchrp_rpt_500 v 22. pdf

Children