Prius (& other hybrids) claim better economy in stop & go city driving than on the highway. This is for two reasons:
> Parasitic drag is less at lower speed (forgive my aeronautical lingo - parasitic drag is the only kind of drag a car has!)
> Regenerative braking recharges the battery (for free) every time you use the brakes.
So if the comparision is made on the highway, a hybrid is less of an advantage - or maybe no advantage at all. OTOH, city buses, taxicabs and urban delivery vehicles might be excellent candidates for hybrids.
