CMF / CRF Details

CMF ID: 6167

Lower posted speed from 160 km/h to 140 km/h

Description: Reducing the speed limit from 160 km/h to 140 km/h

Prior Condition:  Speed Limit 160 km/h

Category: Speed management

Study: A Study of the Safety Impact of Speed Limit Reduction on Abu Dhabi Freeways, Abdelany et al., 2014

 
Star Quality Rating:4 Stars  [View score details]
Rating Points Total:110
Crash Modification Factor (CMF)
Value:0.8172
Adjusted Standard Error:
Unadjusted Standard Error:0.7763
Crash Reduction Factor (CRF)
Value:18.28  (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:77.63
Applicability
Crash Type:All
Crash Severity:A (serious injury)
Roadway Types:Principal Arterial Other Freeways and Expressways
Street Type:
Minimum Number of Lanes:2
Maximum Number of Lanes:3
Number of Lanes Direction:
Number of Lanes Comment:
Crash Weather:Not specified
Road Division Type:Divided by Median
Minimum Speed Limit:160
Maximum Speed Limit:160
Speed Unit:km/h
Speed Limit Comment:
Area Type:Not specified
Traffic Volume:
Average Traffic Volume:53723 Annual Average Daily Traffic (AADT)
Time of Day:All
If countermeasure is intersection-based
Intersection Type:
Intersection Geometry:
Traffic Control:
Major Road Traffic Volume:
Minor Road Traffic Volume:
Average Major Road Volume :
Average Minor Road Volume :
Development Details
Date Range of Data Used:2006 to 2011
Municipality:Abu Dhabi
State:notusa
Country:United Arab Emirates
Type of Methodology Used:Before/after using empirical Bayes or full Bayes
Sample Size (sites):28 sites before, 28 sites after
Sample Size (site-years):112 site-years before, 28 site-years after
Sample Size (miles):208 miles before, 208 miles after
Sample Size (miles):832 mile-years before, 208 mile-years after
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:Mar 12, 2015
Comments:This CMF is for the road called "Alsela". Data from one route was used as a comparison group. The number of crashes in the after period were not reported in this study, however, they have been recorded as 300 to give 10 points as a beneift of doubt for one or more of the following: (1) number of miles/sites in the reference/treatment group, (2) number of crashes in the references/treatment group, (3) reporting AADTs for the aggregate dataset but not for the disaggragate dataset used for CMF development.