Resolution_Snoqualmie Pass Comprehensive Safety Action Plan

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Appendix K | 2 Methodology An Origin–Destination (OD) analysis was conducted for Snoqualmie Pass, WA using StreetLight data to understand travel patterns by season and day type. Two seasonal periods were analyzed: •Summer (July 1 – September 30, 2024) •Winter (January 1 – February 29, 2024, and December 1 – 31, 2024) Average weekday and weekend day travel patterns were developed for each season: •Weekday averages were calculated from Tuesday through Thursday trip data. •Weekend averages were calculated from Saturday and Sunday trip data. The OD analysis considers all vehicle trips that start or end in Snoqualmie Pass and pass-through the I-90 Exit 52 or Exit 53 northbound or southbound ramps, as these roadways provide the only direct access to Snoqualmie Pass. StreetLight data was aggregated from the Census Block Group level to the Census Tract level to summarize estimated average daily trips to and from Snoqualmie Pass. The two census tracts that physically contain Snoqualmie Pass were excluded from visualization and analysis because every trip to the Pass either starts or ends within these tracts. Including them would have obscured regional travel patterns, so they were omitted to better illustrate where trips to and from Snoqualmie Pass originate and end across the broader region. Mapping outputs illustrate vehicle trip estimates between each census tract and Snoqualmie Pass. Darker tracts indicate greater trip activity, while lighter tracts show fewer daily trips. Separate maps were produced for: •Average winter weekend day •Average winter weekday •Average summer weekend day •Average summer weekday Findings On an average winter weekend day, travel activity to and from Snoqualmie Pass was at its highest, reflecting strong recreational demand associated with skiing and snow play. An estimated 6,800 average daily trips occurred between Snoqualmie Pass and surrounding regions. Most of these trips were between Snoqualmie Pass and census tracts west of the Pass, including Seattle (about 12% of trips), North Bend (about 10% of trips), Issaquah (about 8% of trips), Bellevue (about 6% of trips), and Snoqualmie (about 5% of trips), while trips east of the Pass primarily originated in and around Cle Elum (about 5% of trips). This pattern demonstrates the predominance of winter recreation travel from the Puget Sound region, with comparatively limited trip activity from eastern Washington. On an average winter weekday (based on Tuesday through Thursday travel), trip volumes were substantially lower than on weekends, reflecting more typical local or operational travel rather than recreation. Approximately 3,000 average daily trips occurred to or from Snoqualmie Pass. The majority of weekday trips connected the Pass with jurisdictions along the I-90 corridor, including