There is a fence with a gap. Looking at Google satellite view, the "trail" inside the fence is an arbitrary line, not a trail. I was told by a school district employee there that access beyond that fence is limited, and it seems odd that a trail would cross a track for athletic competition at a random spot on a curve. I believe my edit reflects more accurately what exists in the real world.

You are correct-thanks. From conversation with workers on-site, fence will probably be removed by July 2026. Also, they said there is a plan to connect 2nd Ave. to 3rd Ave. just to the south. So this will change again.

Presumably from 2nd Ave. NE. I have been using Wandrer to ride all my local roads, and then rechecking spots that proved to be inaccessible. Also have been finding things like this near the current light rail construction zones. I will ride back there and verify before I make another edit. It appears that there is a driveway that may connect to 2nd Ave. through the dark area between 15401 and 15451B.