According to US Census Bureau data, in the last two decades, Yelm’s population has increased more than threefold, from 2,700 in 1998 to over 9,100 in 2018. With the increase in population and the increases in regional traffic, congestion has worsened within the downtown corridor.
During fall 2017, the City of Yelm collected traffic counts during what is called the PM peak hour. A PM peak hour is the 60-minute interval that contains the largest volume of traffic during a given time period. Using these counts, PM peak hour traffic volumes along SR 510/SR 507 (Yelm Avenue) through the City of Yelm were calculated. The traffic counts indicate that hundreds of vehicles use Phase 1 of the SR 510/Yelm Loop during the PM peak hour, illustrating the traffic diversion that is already occurring via Phase 1 and local roads.
The Phase 2 build alternative would help pull regional traffic out of downtown Yelm and encourage regional traffic to use the Yelm Loop instead of using local roadways to bypass the downtown area. By completing the Yelm Loop, regional travelers would have an alternative to bypass downtown Yelm and regional traffic would experience faster travel times through Yelm. An estimated two-thirds of regional traffic would use the new SR 510/Yelm Loop (see table).
Regional trips would account for 50% of eastbound and 80% of westbound traffic on the new roadway. This shift of regional traffic would reduce congestion in downtown Yelm and reduce pressure on local roads. By allowing regional traffic to bypass downtown, the Build Alternative would increase capacity and improve the overall efficiency of traffic in Yelm.
In the opening year (2022), traffic using Yelm Avenue would receive minimal time savings, but regional traffic on Yelm Loop would see travel times reduced by about 40%. In 2040, traffic is projected to experience more significant improvements compared to the No Build Alternative. Travel time on Yelm Avenue would be 17 minutes in the eastbound direction, as compared to 28.5 minutes in the No Build Alternative – a savings of approximately 40%. In the westbound direction on Yelm Avenue, travel time would be 13.5 minutes compared to 17 minutes with the No Build Alternative, about a 20% reduction. Regional traffic using Yelm Loop in 2040 would experience travel time savings of over 50% in both directions compared to the No Build Alternative.