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CENTERVILLE RD (CSAH 21/CSAH 59) AT ASH ST (CR J)/WILKINSON LAKE BLVD PAGE 15 ICE REPORT S.A.P. TBD WSB PROJECT NO. 2988-080 CITY OF LINO LAKES, MN Table 4: Existing and Projected Crash Rates by Traffic Control Type Traffic Control Crash Reduction Factor* Crash Rate** Projected Crashes Per Year Through-Stop (existing) NA NA 0.60 Signalized (Metro district average rate) NA 0.18 0.18 Urban Single Lane Roundabout 0.60 0.38 0.36 Urban Multi-lane Roundabout 0.65 0.41 0.39 * Crash reduction factors taken from MnDOT's HSIP Program guidance ** Crash rate for proposed improvements = crash reduction factor multiplied by the existing intersection crash rate A traffic signal would cut the crash rate by over two-thirds greatly improving the safety of the intersection. A single or multi-lane roundabout would also cut the crash rate by roughly one- third, which would make it an effective safety measure as well. Intersection Capacity Evaluation Intersection operations are evaluated in terms of average seconds of delay per vehicle for the intersection, and for each approach and turning movement. The average number of seconds of delay is broken into six ranges assigned letter grades A through F defining each level of service (LOS) as shown in Figure 9. The ranges for un-signalized intersections are narrower than the ranges for signalized intersections. This is because many factors including the intangible factors of driver discomfort and frustration are considered. Studies have indicated that a one-minute delay at a red light is perceived as being more tolerable than one minute waiting for a gap in traffic at a stop sign, especially when there are vehicles queued behind. It is generally recognized that LOS D is the lowest acceptable LOS for urban intersections. Intersection capacity is also defined in terms of queue lengths of stopped vehicles. A 100-foot queue is approximately equal to four cars.