A bus trap is a road construction or device that only allows buses to pass through.
Fullsize image: https://s3-us-west-1.amazonaws.com/h...p_fullsize.jpg
https://s3-us-west-1.amazonaws.com/h...h_bus_trap.jpg
Previously:
https://www.homemadetools.net/forum/...812#post167499
https://www.homemadetools.net/forum/...086#post130094
https://www.homemadetools.net/forum/...038#post168348
https://www.homemadetools.net/forum/...817#post171165
https://www.homemadetools.net/forum/...230#post165507
https://www.homemadetools.net/forum/...367#post173313