There are a few things your contractor will consider when deciding on the width of your driveway. The size of the area where the driveway will be poured will dictate the width but it is often around the 3m range. It needs to be wide enough for a vehicle to ride on without its wheels slipping off the edges. If your driveway is lifted off the ground, wheels pressing against its edges every so often will lead to it chipping and chunks of it breaking off eventually.