slipway

noun

1. A sloping surface, leading down to the shore or to a river, on which ships are built, repaired or stored and from which they are launched.
2. A slip road.

   “Immediately beyond the 'No entrance' sign onto the motorway slipway, turn right down the bank.”

   “Cross a motorway slipway – there are no traffic lights. Then cross a major junction. Keep the motorway on your left.”