motorcycle police officer
Refers specifically to a uniformed officer who patrols on a white police motorcycle (白バイ).
See also: 白バイ (しろバイ)
A motorcycle police officer pulled over a car for a traffic violation.
Compound of 白 (しろ, 'white'), バイ (from オートバイ, 'motorcycle'), and 隊員 (たいいん, 'member of a squad'). The white color is associated with Japanese police motorcycles.