In Bellingham, section of South Bay Trail is now temporarily closed due to more housing construction.

There is a street detour. I've mapped my own detour which I modified for going north along 12th. The main Boulevard route works okay for going south.

My route avoids crossing the boulevard to northbound side where there might not be a stoplight or flashing crosswalk. One can ride on sidewalk, however.

Detour follows the main boulevard, but for going northbound, I prefer 12th. This avoids using 10th and crossing the boulevard, to northbound side, where there isn't a light. the main boulevard, in that area is called 11th St.

Graffiti on a "trail closed" sign. Yes. Bellingham is a popular city. There is population and economic growth.

Toward the north end of 12th (at Adams ) there is a flashing crosswalk across the boulevard at the access road to Boulevard Park.

I have often used South Bay Trail Route between downtown and Fairhaven District. Then come back north through Western Washington University for variety and a fitness hill climb, myself.

There are various ways to go.