carpool lane

US /ˈkɑːr.puːl ˌleɪn/
UK /ˈkɑːr.puːl ˌleɪn/
"carpool lane" picture
1.

a lane on a highway reserved for vehicles carrying a specified minimum number of passengers, typically two or more, to encourage carpooling and reduce traffic congestion

:
During rush hour, the carpool lane moves much faster.
You need at least two people to use the carpool lane.