PD-17-00001 Marian Meadows Full Record with Index (2)

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Marian Meadows Rezone and Subdivision Final Environmental Impact Statement 3-94 Widening the northbound approach (Railroad Street) to include a left-turn lane and eliminating the stop signs on the eastbound approach (Sparks Road) and northbound approach to allow through movement from Railroad Way to Sparks Road would improve operations to LOS C and with 15.8 seconds/vehicle of delay. However, this configuration may be confusing to some drivers and the eastbound approach movements would need to yield to multiple other movements and could pose safety concerns. Alternatively, construction of a roundabout would allow the high-volume non-conflicting movements to move freely through the intersections while concurrently accommodating the other low-volume movements. With the roundabout, operations at this intersection would improve from LOS F and 153.5 seconds/vehicle of delay to LOS A with 6.0 seconds/vehicle of delay. Addition of a median refuge (merging area) for southbound left movements from Pit Way onto Sparks Road would improve this intersection’s operations from LOS E to acceptable LOS C with 17.3 seconds/vehicle of delay. The potential need for left-turn lanes at the on Sparks Road intersection with Pit Way/Hawthorn Lane was examined in detail. The left-turn volume from Sparks Road to Pit Lane is relatively low (because it continues to serve only the existing subdivision) and does not justify a left-turn lane. Under the cumulative growth scenario, the critical movement is the northbound turn movement from Hawthorn Lane into Sparks Road. The potential mitigation would be a median refuge lane on Sparks Road for these left turns. This feature was evaluated with respect to the WSDOT guidance in Exhibit 1310-12a. At Pit Way, the left-turn volume is 34 vph, which represents roughly 4 percent of the through-movement volume and would not justify a refuge lane. (Exhibit 1310-12a guidance is limited to roads with speed limits of 40 mph, which is slightly higher than Sparks Road, but may represent actual operating conditions). The need for construction of a left-turn lane should be monitored based on actual volumes experienced in the future. At Country Drive, the left-turn volume increases to 151 vph because this roadway serves as a primary access point to the project. With this volume, which represents approximately 26 percent of the through- movement volume, a left-turn lane would be desirable. At the West Sparks Access point, the left turns, 231 vph, constitute the majority of the total entering volume, but the opposing through-movement volume, 81 vph, is very low and therefore a turn lane would not be needed. Mitigation for collisions Although traffic volumes are expected to substantially increase, and therefore increase the collision potential, the primary safety concerns are at intersections where delays are excessively high and people drive more aggressively. By mitigating the operational deficiencies at the I-90 eastbound ramps/Railroad Street and Sparks Road/Railroad Street intersections, potential traffic safety concerns would also be mitigated.