U-turning when coming off south bound A1

Drivers are crossing the A1 from the Southbound carriageway at Wittering then then turning straight back onto the slip road for the northbound carriageway of the A1. This can cause the vehicles behind who are crossing at the same time to be left sitting on the A1 northbound carriageway with fast moving traffic heading towards them and in danger of being hit. The junction is designed so this should not happen but that is not stopping them. I have personally come from the village and witnessed a number of vehicles doing a u-turn and then entering the RAF base. This is putting peoples lives in danger and needs to stop.