The Federal Way Link Extension is a new light rail line that connects the Seattle-Tacoma International Airport (SEATAC) to Federal Way Station, ~8 miles away. The aerial guideway Structure C located at South 272^nd St Station has five specifically designed Shock Transmission units (STUs), also known as Lock-Up Devices (LUDs), at the end piers. The STUs allow the bridge to ‘lock-up’ in a seismic event, act monolithically and to load share with the adjacent main piers. This reduces the demand on the end piers and protects the piers from overloading.

The STU is also designed to carry daily service movement influenced by thermal creep and shrinkage as well as train braking protecting the bridge from excessive fatigue.

This new structure will help connect 34,000 people daily to and from SEATAC and Federal Way respectively in 15 minutes whilst reduced demand on neighboring Interstate 5.