motorcycle police; traffic police on motorcycles
Refers to the officers or the unit, not just the vehicle. Abbreviation of 白バイ隊員.
See also: 白バイ隊員
The motorcycle police were directing traffic at the intersection.
white police motorcycle
Specifically the white-colored motorcycle used by Japanese traffic police. Often seen in the phrase 白バイに乗る.
The white police motorcycle sped away with its siren on.
A police officer on a motorcycle was riding along the highway.
I was going too fast and got pulled over by the motorcycle police.
The motorcycle police were chasing the fleeing car.