I used to ride through a bike/pedestrian underpass that had a 90 degree at one end on my way to/from my old office. Kids used to like to skateboard down the hill at the other end before going into the tunnel and liked to scare people if they could. My riding through it after dark would definitely get peoples attention if they were coming the other way and couldn't see into the tunnel. They weren't sure what was coming, but they knew something was and yes I always covered my lights when passing, even for the kids on skateboards.