built in 1982, the a12 colchester bypass provides an uninterrupted dual carriageway where the national speed limit of 70 mph applies. before 1982, the a12 took a route much closer to colchester itself, and although still a bypass it consisted of urban single carriageways with roundabouts and pedestrian crossings. the old bypass is still in existence – the western half now forms part of the a1124 and the eastern half part of the a133.