Final answer:
A carpool lane is identified by a diamond symbol and is reserved for high-occupancy vehicles to encourage carpooling.
Step-by-step explanation:
A carpool lane is typically marked with a diamond symbol. Specifically, when you see a diamond symbol painted on a road lane or on road signs adjacent to the lane, this indicates that the lane is reserved for carpool or high-occupancy vehicle (HOV) use. These lanes are meant to encourage carpooling and reduce traffic congestion by allowing vehicles with multiple occupants to bypass regular traffic.