Refined I-405 BRT to Speed Buses, Attract More Riders

Planned project refinements add up to much better travel times for riders than anticipated in 2016 (Image: Sound Transit)

Sound Transit has significantly refined the design for I-405 BRT which is anticipated to begin service in 2024. The final set of refinements from Phase 1 of design were shared with the System Expansion Committee at their March meeting. The design changes reduce travel times on the corridor and improve reliability. The shorter travel times make the service more appealing and ridership estimates have been raised correspondingly.

Construction will mostly occur in 2023-2024. WSDOT will begin construction of two stations (NE 44th in Renton and NE 85th in Kirkland) much earlier. Both are lengthier and more complex projects, and NE 44th is scheduled as part of the widening of I-405 south of Bellevue starting in 2019.

At the north end of I-405, the representative project envisioned buses running in general purpose lanes between Lynnwood and Brickyard. Although it would be faster to operate in the HOT lanes, the HOT lanes lack center exits to several stops in the Bothell area, setting up an awkward trade-off of speed vs access. Sound Transit has now identified several new locations where the buses can operate on the shoulder. Combined with existing bus-on-shoulder operations, the BRT will be able to operate on the shoulder for most of the distance between Lynnwood and Brickyard southbound while still serving all planned stations. As this is the most congested part of I-405 (and the only part where toll lanes have not met targets for 45mph travel 90% of the time) the benefits of getting buses out of general traffic will be significant.

In the northbound direction, a short stretch of new bus-on-shoulder lanes will be added to the existing peak hour general purpose shoulder driving between SR 524 and I-5.

In Kirkland, Sound Transit has abandoned a proposal for bus-only lanes between the NE 85th BRT station and downtown. The transit lanes through the highway intersection will stay in the plan, but study found little benefit to bus travel times from lanes between 114th and 6th St. Savings will be redirected to more strategic speed and reliability improvements. Sound Transit will also fund improved pedestrian connections to the station.

The latest design for the Tukwila BRT station moves the stops alongside the freeway with a pedestrian bridge connection to the rail station (Image: Sound Transit)

In Tukwila, the planned BRT station will be moved. It was previously envisioned that buses would exit the freeway to BRT stops at the Link station. Sound Transit now proposes a pair of BRT stops on either side of SR 518 so that buses would not need to exit the freeway. A pedestrian bridge would connect both stops to the Link station and might extend further south to enable walk-up connections from across the freeway.

These design updates are accompanied by a long list of minor modifications including transit signal priority and queue bypass at several stations. (Click for details for North and South). The net result is much faster travel along the corridor. Five minutes are shaved off travel times on the North Corridor (Bellevue - Lynnwood). Seven to nine minutes are saved on the South Corridor (Bellevue - Burien). The time savings improve ridership. Models project 12% more boardings in the north, and 22% more in the south, for a combined 19,200 to 25,800 riders in 2040. That's 17% better than earlier estimates.

At the north end, Sound Transit is coordinating with WSDOT plans for a second HOT lane, though the schedule is dependent on funding from the Legislature. Those would move the Canyon Park stop to an inline station in the center lanes. Implications for the Brickyard stop are still being considered.

The connection between SR 522 BRT and I-405 BRT led to controversy which Martin described in February. At a meeting of elected leaders Friday, staff described their proposal to extend SR 522 BRT to the 195th St station with 10 minute headways (the low ridership segment to Woodinville would remain at 20 minutes). That makes for more frequent connections to I-405 BRT for riders from Bothell and UWB without having buses divert from I-405.