People gathering for sex in lay-bys along a main road in East Yorkshire are being given warning leaflets by police.
Officers have been monitoring the area along the A165 near Coniston after complaints about so-called “dogging”.
Humberside Police said 18 people had been spoken to in one month. Some were found half-dressed, but claimed to be there for “legitimate reasons”.
Hedges have been cut down to deter would-be participants.
The force said it was responding to concerns expressed by residents in the small village of Coniston, which is outside Hull.
Although the area is rural, there are a number of houses near to where the leaflets have been issued on the A165, which runs between Hull and Bridlington.
The force told residents their investigations had discovered a number of people at the sites.