Road-distance delivery pricing
Road-distance delivery pricing charges by the distance a driver actually drives rather than by a straight line on a map. A radius measures the crow-flies distance; a driver cannot drive a straight line. Road-distance pricing asks a routing service for the real driving distance and charges in bands based on it, so two addresses the same distance away can correctly cost different amounts to reach.
In practice
A radius drawn on a map measures the straight line from your shop to the customer. A driver cannot drive a straight line. Road-distance pricing asks a routing service for the real driving distance, and charges in bands based on that.
The gap between the two is largest exactly where it costs you most: across a river with one bridge, on the wrong side of a dual carriageway, or in an estate with a single entrance. Two addresses the same distance away as the crow flies can be a four-minute and a fourteen-minute drive.
It is slightly more work to set up, because it needs a routing provider and sensible fallbacks for when that provider is slow. In return, the charge matches what the drop actually costs, and you stop losing money on the far edge of every zone.
Also called: driving distance delivery charge, distance based delivery.