The night shift that keeps a city moving

The baton glows red, the reflective vest catches the headlights, and for eight hours this junction belongs to one person. Night-shift traffic duty is not glamorous work, but on a city ring road it is what keeps deliveries, ambulances and the last buses flowing.

The rhythm is unpredictable. Long stretches of nothing are broken by a convoy of lorries or a breakdown in the outside lane, and the response has to be instant. The warden we followed had cleared two stalled vehicles before two in the morning.

The city is trialling cameras and adaptive signals at its busiest crossings, but the people on the ground remain the fallback when the technology fails. On this night, at least, it did not.