CMF / CRF Details
CMF ID: 4734
Convert a conventional unsignalized intersection to an unsignalized superstreet
Description:
Convert a conventional unsignalized intersection to an unsignalized superstreet (also known as a restricted crossing U-turn intersection or a J-turn intersection)
Prior Condition: conventional unsignalized intersection
Category: Intersection geometry
| Crash Modification Factor (CMF) |
|---|
| Value: | 0.41 |
| Adjusted Standard Error: | |
| Unadjusted Standard Error: | 0.12 |
| Crash Reduction Factor (CRF) |
|---|
| Value: | 59 (This value indicates a decrease in crashes) |
| Adjusted Standard Error: | |
| Unadjusted Standard Error: | 12 |
| Applicability |
|---|
| Crash Type: | Left turn |
| Crash Severity: | All |
| Roadway Types: | Principal Arterial Other |
| Street Type: | |
| Minimum Number of Lanes: | |
| Maximum Number of Lanes: | |
| Number of Lanes Direction: | |
| Number of Lanes Comment: | |
| Crash Weather: | Not specified |
| Road Division Type: | Divided by Median |
| Minimum Speed Limit: | |
| Maximum Speed Limit: | |
| Speed Unit: | |
| Speed Limit Comment: | |
| Area Type: | Rural |
| Traffic Volume: | |
| Average Traffic Volume: | |
| Time of Day: | All |
| If countermeasure is intersection-based |
| Intersection Type: | Roadway/roadway (not interchange related) |
| Intersection Geometry: | 3-leg,4-leg |
| Traffic Control: | Stop-controlled |
| Major Road Traffic Volume: | Minimum of 5900 to Maximum of 33500 Annual Average Daily Traffic (AADT) |
| Minor Road Traffic Volume: | Minimum of 330 to Maximum of 5000 Annual Average Daily Traffic (AADT) |
| Average Major Road Volume : | |
| Average Minor Road Volume : | |
| Development Details |
|---|
| Date Range of Data Used: | 1991 to 2010 |
| Municipality: | |
| State: | NC |
| Country: | U.S.A. |
| Type of Methodology Used: | Before/after using comparison group |
| Other Details |
|---|
| Included in Highway Safety Manual? | No |
| Date Added to Clearinghouse: | Jun 04, 2012 |
| Comments: | This CMF was obtained from Table 3.13 for “left turns” crashes from the unsignalized set (p. 83). The years of data were obtained from Table 10.2 (p. 161). The sample size for the treatment group (total) was 102 crashes. According to the executive summary, all the superstreet sites have a rural area type (p. iv). The minimum and maximum major roadway AADTs were obtained from Table 10.4 (p. 163), and the minimum and maximum minor roadway AADTs were obtained from Table 10.5 (p. 164). The number of legs of intersections was obtained from Table 10.3 (p. 162). The after periods of some of the sites were rather short (i.e., < 1 yr). See Table 10.2 (p. 161). 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. |
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