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Existing Transportation Conditions Table 2-2 Level of Service Definitions Level of Service Interpretation V/C Ratio A Uncongested operations; all queues clear in a single Less Than 0.60 signal cycle. B Very light congestion; an occasional approach phase is 0.60-0.70 fully utilized. C Light congestion; occasional backups on critical approach- 9.700.71-0.80 es. D Significant congestion on cdtical approaches, but:intersec- C.S90.81-0.90 tion functional. Cars required to wait through more than one cycle during short peaks. No longstanding queues formed. E Severe congestion with some long-standing queues on 0.900.91-0.99 cdtical approaches. Blockage Of intersection may occur if traffic signal does not provide for protected turning move- ments. Traffic queue may block nearby intersections(s) upstream of critical approach(es). F Total breakdown, stop-and-go operation. 1.00 and Greater A signalized intersection's level of service can be calculated with a n-tuber of methods. For this study, a method based on critical movement analysis, called the VCCC method was used. VCCC stands for Volume-to-Capacity Contra Costa County. See Appendix A for a full description of the VCCC program. This method is identical to the Circular 212 method except that the saturation flow is increased from 1,500 to 1,800 vehicles per hour. This adjustment was based on saturation-flow rate studies conducted by CCTA in Contra Costa County. The volumes of cars on a critical movement are s-tamed and divided by the capacity of the movement. This V/C ratio of each critical movement at an intersection is used to produce an overall intersection V/C ratio also taking into account signal phasing. The overall V/C ratio is then correlated to a level of service (see Table 2-2). AM peak-hour and PM peak-hour levels of service are shown by city in Table 2-3. Barton-Aschman Associates, Inc. 25