point duty 
noun [mass noun] British
The duties of a police officer or other official stationed at a junction to control traffic: if necessary extra officers would be placed on point duty...
- The policeman on point duty at the junction of Nessgate and Spurriergate in York was expected to have grown accustomed to strange sights, especially during the Festival.
- I remember when there was a police officer on point duty at the top of Finkle Street.
- In real Test matches, teams tend to defend rather than wave the attacker through like a policeman on point duty, which is what happened in the Currie Cup final.