It is set to comprise three lines that cover 46 miles (74 km) and 25 stations on Interstate 405 (I-405) and State Route 522 (SR 522) in King and Snohomish counties.

Funding for the I-405 BRT lines, along with the addition of the SR 522 corridor, was part of the Sound Transit 3 ballot measure that was passed by voters in 2016.

[5][6] The south half of I-405 is served by Route 560, which travels from the Westwood Village shopping center in West Seattle to Burien, Seattle–Tacoma International Airport, Renton, and Bellevue.

[2] The SR 522 corridor from Seattle to Kenmore, Bothell, and Woodinville is served by Sound Transit Express route 522, which launched in September 2002.

[11] I-405 was originally built as a bypass around Seattle, but had become heavily congested during peak hours after the development of Eastside cities in the late 20th century.

[13] The ramps were funded by the Sound Move ballot measure, which was approved by voters in 1996, and intended to be a precursor to a bus rapid transit (BRT) system.

[17][18] The state government convened a 19-member committee in 2001 to draft a long-range plan for the I-405 corridor that would be used to recommend projects in future legislative funding packages.

[22] The BRT project was bundled into the unfunded phase of the corridor's master plan, which would take an estimated 20 years to construct with additional funding sources.

[28][29] Cities on the north side of Lake Washington had also unsuccessfully requested funds to study transit options for the SR 522 corridor in the package.

It included BRT on the I-405 corridor, which was also designated for potential rail expansion, and an unspecified form of high-capacity transit on SR 522 and between Bothell and Kirkland.

[33] In August 2015, Sound Transit revised the preliminary list of projects in the package to include BRT on SR 522 alongside I-405 and the Eastside Rail Corridor.

[48] In 2019, Washington State Department of Transportation (WSDOT) began construction of Renton–Bellevue HOT lanes on I-405, which includes a rebuilt interchange for the Stride S1 Line.

[56] It replaces an existing cloverleaf interchange east of downtown Kirkland with two roundabouts that segregate HOT lane traffic and include stops for the intersecting RapidRide K Line.

[62][63] The system's 25 stations[61] will include large shelters, off-board fare payment, ticket vending machines, and real-time information screens.

[63] The Stride lines are expected to have end-to-end travel times that average 20 minutes faster than existing express bus routes on those corridors.

[54] The sole operations and maintenance facility for Stride is Bus Base North, located in the Canyon Park neighborhood of Bothell.

[58][59] Stride is planned to use a fleet of 48 battery electric buses with wireless inductive chargers embedded into the roadway at layover facilities.