By Miki Mullor
Editor

• Sahalee way is failing concurrency due to large car volumes.
• Staff suggest adding a median and left turn pockets to pass concurrency.
• Town Center’s first building application currently cannot pass concurrency.

Key decision on traffic tonight

The Sammamish City Council tonight will consider left turn lanes and other improvements to Sahalee Way in an effort to ease traffic concurrency calculations that essentially shuts down further development of the Town Center.

Other projects are also halted because analysis of the volume-to-capacity (V/C) ratios for Sahalee Way show the road is failing and cannot accept any more traffic.

If the council accepts recommendations from staff, new development can win approval for traffic concurrency testing.

Failure today, pass tomorrow

The V/C thresholds for road segments and corridors, 1.4 V/C and 1.1 V/C respectively, recognizes a failure of the Sahalee Way-228th Avenue North Corridor, which has a V/C exceeding the 1.1 V/C threshold for corridors.

The Sammamish City Council tonight will consider left turn lanes and other improvements to Sahalee Way in an effort to ease traffic concurrency calculations that essentially shuts down further development of the Town Center.

Other projects are also halted because analysis of the volume-to-capacity (V/C) ratios for Sahalee Way show the road is failing and cannot accept any more traffic.

If the council accepts recommendations from staff, new development can win approval for traffic concurrency testing.

Failure today, pass tomorrow

The V/C thresholds for road segments and corridors, 1.4 V/C and 1.1 V/C respectively, recognizes a failure of the Sahalee Way-228th Avenue North Corridor, which has a V/C exceeding the 1.1 V/C threshold for corridors.

With direction from city staff, the city’s traffic modeler, David Evans and Associates (DEA), tested the effects of seven strategies to improve operations on the failing corridor. The following table illustrates the strategies the City could implement and their impact on the V/C for the failing corridor. Only the AM Peak Hour Northbound is shown because that is when the corridor is most congested.

Town Center halted

As we reported, the Town Center’s first building application for 424 homes and 82,000 SF of commercial space is currently blocked due to the concurrency failure on Sahalee Way.

“In addition to the above strategies, the City Council could choose to raise the V/C standard for the Sahalee corridor, exclude it from concurrency measurement similar to East Lake Sammamish Parkway, or identify a capital project(s) on the TIP that increases capacity on the corridor, ” the staff tells council.

While the proposed improvements may allow development to pass concurrency, what is missing from the proposal are previously discussed projects to add lane capacity and inter-local agreements with Redmond and King County to address the choking points at the city limits.

Since 2003 the city recognized inter-local agreements are key to improve traffic flow at the exit routes given the Sammamish is landlocked.

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