There were a total of 11 left turn crashes involving eastbound left turning vehicles and westbound through vehicles at the intersection of Shroyer Road and Dorothy Lane. Two of the 11 crashes were attributed to red light running of westbound through traffic. The motorist turning left was at-fault for the remaining 9 crashes.

Figure 6 shows the sight line of an eastbound left turning motorist (150 feet). The sight distance of 150 feet or less is available when an opposing westbound left turn vehicle is present. The horizontal curvature of Dorothy Lane reduces the available sight distance at the Shroyer Road intersection. The ODOT Location and Design Manual, Volume 2, Figure 201-1E suggests a minimum stopping sight distance of 250 feet for speeds of 35 miles per hour. The available sight distance is not adequate for approach speeds greater than or equal to 25 miles per hour.

The existing signal phasing is a protected/permissive phase for both the eastbound and westbound left turn movements. Opposing left turning vehicles restrict sight distances to lengths less than the posted speed limit on Dorothy Lane. Changing the protected/permissive left turn phase to protected only phasing is recommended unless the intersection sight distance is improved to meet minimum criteria. Progression on Dorothy Lane will need to be evaluated by others to determine if lead/lead or lead (EB)/lag (WB) is preferred to reduce stops.

Implementation costs of $6,000 are estimated for a new signal head, signal timing analysis, and new signal cables.