Lane Mile
A lane mile is a mile of roadway in a single driving lane. The total lane mileage of a highway is found by multiplying the centerline mileage of a road by the number of lanes it has. Lane mileage is the total amount of mileage covered by a road's lanes.
Illustration: Centerline Miles
Source: The illustration above represents what the public will see on our highways as Centerline Miles.
TxDOT Visual Dictionary