The Red Loop is a nice 4.4-mile pedal around the entire campus. It is a mix of cedar chips, dirt trails, and paved sections with a few short but significant climbs.
There are some stairs on the lower bridge. If you pedal counter-clockwise, you can ride down the stairs. The west side of the campus is easier to ride counter-clockwise.
There are multiple places you can start this ride from and it can be run clockwise or counter-clockwise. The entire trail map is posted at the trailheads and if you happen to go off course, don't worry, as you'll run into one of the many connectors.
Starting at the field on 50th, heading clockwise, pedal around the field heading south. Then hang a left and drop down the dirt road. This drops you at the WSU Barn. Follow the chip covered trail and hang a left and go over the bridge. From there, you run across the open spaces on the south end of campus. There are a lot of connector trails that intersect the trail, but generally stay to the left.
You'll pedal over a mix of dirt, wood chips, and raised boards. Just keep following the path around the campus. You'll make a few more lefts until you go across the bridge, then you'll be heading down the trail to the northeast Salmon Creek Ave entrance.
As an optional ride, from the entrance, you can ride up the road with the cars, or go for an adventure through the user trails along the property line. If you want to ride on the primitive trail, go to NE 35th Ave. and take a right about 20 yards up the road, this is the second 'landing.' Follow that up and along the fence line. This will zig zag its way up to the neighborhood and basketball courts. The University is a bit lax mowing the path, as it has been taken over by tall grass. Depending if they have mowed or not, it may be cleared where you are going, or you'll just have to follow the fence on your left to 29th/30th.
The main loop follows the road, then picks up the cedar chip trail again at the basketball court/parking lot on your left. Follow this and it will be clear where to proceed. If you need guidance, just take a look at one of the many maps scattered along the way or use the MTB Project mobile app