Question about the incident of a policeman with a UFO with a serial number that seems to start with TL.

In which incident (I can't find it) was a policeman, probably in 1965 or 1975, driving on a US highway at night and turning onto a side road. He then encountered a bus-shaped UFO with several beings next to it.
He stopped his car early and hid on the shoulder, but when the beings saw him, they got into the UFO and flew away.
The UFO had some serial number or something like that, I don't remember what it was, but I think it was something like TL4867, and the officer remembered that number.