Adopted Level of Service Standards for Regionally Significant State Highways

In compliance with 1998 amendments (HB 1487, the “Level of Service Bill”) to the Growth Management Act (GMA) the Puget Sound Regional Council Executive Board adopted level of service (LOS) standards for regionally significant state highways in the central Puget Sound region. Regionally significant state highways are state transportation facilities that are not designated as being of statewide significance (also called non-HSS).

Level of Service Standards

This table (along with the map) explains the level of service standards.

TierLOS StandardDescription
1LOS "E/mitigated"Tier 1: For this process, the "inner" urban area is generally defined as a 3-mile buffer around the most heavily traveled freeways (I-5, I-405, SR 167, SR 520, and I-90), plus all designated urban centers (most are located in the freeway buffer already). The standard for Tier 1 routes is LOS "E/mitigated," meaning that congestion should be mitigated (such as transit) when p.m. peak hour LOS falls below LOS "E."
2LOS "D"Tier 2: These routes serve the "outer" urban area - those outside the 3-mile buffer - and connect the "main" urban growth area (UGA) to the first set of "satellite" UGA's (e.g., SR 410 to Enumclaw). These urban and rural areas are generally farther from transit alternatives, have fewer alternative roadway routes, and locally adopted LOS standards in these areas are generally LOS "D" or better. The standard for Tier 2 routes is LOS "D."
3LOS "C"Tier 3: Rural routes are regionally significant state routes in rural areas that are not in Tier 2. The standard for rural routes is LOS "C," consistent with the rural standard in effect for those routes once they leave the four counties in the PSRC region, such as SR 530 entering Skagit County.

The LOS standards do not change within a city. For example, the change from Tier 1 to Tier 2 on SR 516 occurs at the Kent/Covington city limit boundary.

The LOS will be measured consistent with the latest edition (preferred) of the Highway Capacity Manual and based on a one-hour p.m. peak period.