CMF / CRF Details
CMF ID: 8732
Install Variable Speed Limits
Description: The VSL system generally displayed information on dynamic speed limits, lane closures, merge arrows and other warning information through the overhead gantries. Speed adjustments in the system are automated based on real-time traffic conditions.
Prior Condition: Roadway without variable speed limits
Category: Advanced technology and ITS
Study: Evaluating Safety Effects of Variable Speed Limit System using Empirical Bayesian Before-After Analysis, Pu et al., 2017
| Star Quality Rating: |  [View score details] |
| Rating Points Total: | 80 |
| Crash Modification Factor (CMF) | |
|---|---|
| Value: | 0.72 |
| Adjusted Standard Error: | |
| Unadjusted Standard Error: | 0.1 |
| Crash Reduction Factor (CRF) | |
|---|---|
| Value: | 28 (This value indicates a decrease in crashes) |
| Adjusted Standard Error: | |
| Unadjusted Standard Error: | 10 |
| Applicability | |
|---|---|
| Crash Type: | All |
| Crash Severity: | |
| Roadway Types: | Principal Arterial Interstate |
| Street Type: | |
| Minimum Number of Lanes: | 8 |
| Maximum Number of Lanes: | 8 |
| Number of Lanes Direction: | |
| Number of Lanes Comment: | |
| Crash Weather: | Not specified |
| Road Division Type: | Divided by Median |
| Minimum Speed Limit: | 40 |
| Maximum Speed Limit: | |
| Speed Unit: | mph |
| Speed Limit Comment: | > = 40 mph |
| Area Type: | Urban |
| Traffic Volume: | |
| Average Traffic Volume: | |
| 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: | 2007 to 2012 |
| Municipality: | Seattle |
| State: | WA |
| Country: | USA |
| Type of Methodology Used: | Before/after using empirical Bayes or full Bayes |
| Sample Size (crashes): | 327 crashes before, 174 crashes after |
| Sample Size (miles): | 7.23 miles before, 7.23 miles after |
| Other Details | |
|---|---|
| Included in Highway Safety Manual? | No |
| Date Added to Clearinghouse: | Nov 17, 2017 |
| Comments: | CMF of possible injury crashes. |
