The closure of Valley Bridge Parade, and Valley Road beneath the bridge, led to long queues of traffic around the town centre and Weaponness area at teatime rush-hour.
The bridge was closed at lunchtime after Police were called to concerns over the welfare of a young man. Specially trained officers had been brought in.
North Yorkshire Police announced on Twitter at 6pm that roads had reopened.
Valley Road had been closed to traffic at its junction with Westbourne Grove. There was another closure, to pedestrians, at the junction with Grosvenor Road. Valley Road was also closed at its other end, at Aquarium Top.