Highway Code Rule 153 Traffic-Calming Measures.

Traffic-calming measures. On some roads there are features such as road humps, chicanes and narrowings which are intended to slow you down. When you approach these features reduce your speed. Allow cyclists and motorcyclists room to pass through them. Maintain a reduced speed along the whole of the stretch of road within the calming measures. Give way to oncoming road users if directed to do so by signs. You should not overtake other moving road users while in these areas.

Rule 153: Chicanes may be used to slow traffic down.

‍