Chuck
I'm a hyperliler.
My Honda Civic Hybrid's lifetime average is 58.7 MPG.
I drive only in the rightmost lane of several lanes.

Most of the freeway onramps here have two lanes.
One lane is for carpools and there is no waiting.
The other lane has a red light with several waiting cars.
I want to get into that carpool onramp lane.

Also, if my hours at work change and I am forced to drive rush hour, the carpool lane is NOT going at 70 miles per hour so I might use it.

If the regular lanes are gridlocked I will have the freedom to take the carpool lane.