Sound Transit may build inline stop at Brickyard, shifting I-405 BRT to center lanes

At the meeting of the Sound Transit System Expansion Committee on Thursday, an order was approved to begin project development and environmental review on an inline station for I-405 BRT at Brickyard. Along with expanded HOT lanes approved earlier this year, this will allow BRT to operate in managed center lanes along almost the entire length of I-405.

WSDOT and potential Sound Transit investments in I-405 (image: Sound Transit)

The ST3 plan envisioned BRT operating in mixed traffic all of the way from Lynnwood to Brickyard, with buses only moving to the center lanes near NE 128th in Kirkland. This was a necessary outcome of the lack of direct access ramps along the northern stretches of I-405. Earlier this year, Sound Transit identified several new locations where buses could operate on the shoulder, mitigating the impact of general traffic lane congestion.

In the 2019 session, the Legislature approved funding to add a second express toll lane as far north as SR 527. This included direct access ramps at Canyon Park and SR 522, though not at Brickyard. Alone, using these stops would mean skipping Brickyard: buses would need to move from the inside to outside lanes and back to inside again within an infeasibly short distance. Adding a direct access ramp at Brickyard will allow buses to serve all stops while operating continuously in the ETL.

The order approved Thursday allocates up to $7.5 million for project development and environmental review. The eventual cost of the inline station is currently estimated at $75 million. Perhaps $30 million of that will be offset by cancelling previously planned project elements such as I-405 ramp stations and a bus-on-shoulder program north of Canyon Park. Some more savings will come at NE 44th in Renton where that station will be significantly below the representative project budget.

The station closest to downtown Bothell will now be at SR 522, which can be served relatively inexpensively by placing BRT stops on the ramps to the ETL. The off-ramp stops at NE 195th can no longer be served once the BRT moves to the ETL. The long-term vision is an inline stop at NE 195th, but that is not funded at this time. Moving the Bothell stop to SR 522 will have implications, however, for connectivity to UWB, and for the Woodinville leg of SR 522 BRT which might have connected at NE 195th.

The impact on travel times is remarkable, with a one-third reduction in Lynnwood-Bellevue travel times vs the representative project. Travel will also be more reliable. Staff estimate ridership 20% higher than the already improved estimates from phase I design shared in March.

BRT station served by direct access ramps at SR 527 (image: WSDOT)

I-405 BRT is the rare transit project that has become considerably more robust as it proceeds through design. Each successive phase in development has improved travel times and reliability while raising ridership expectations. The buses will now operate outside of managed lanes on I-405 only to access South Renton station and for a brief stretch near the I-5 interchange.

A board decision on I-405 BRT final design, including the Brickyard station, is likely in late 2020. In the meantime, work is proceeding on conceptual engineering, environmental review and cost estimating.