"Motorway speeds" refers to the speed at which vehicles typically travel on a motorway or highway. It suggests a faster pace compared to city or local road speeds. Full definition
In my car, 6th gear at motorway speeds runs at about 2,200 rpm which is hardly doing any work. (mechanics.stackexchange.com)
The Panamera has no problem breaking motorway speed limits regardless of the motive power, yes, it's a Porsche; it goes like stink. (evworld.com)
The vestigial aeroscreen maximises the intensity of the driving exprience, but fitting the optional (detachable) full - width windscreen allows you to cruise at motorway speeds with minimal buffeting. (evo.co.uk)