New-style roundabout tests at Colchester
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• The Transport and Road Research Laboratory, at the invitation of Colchester borough concil, is carrying out an experiment in an attempt to improve traffic flow at the North Station roundabout, Colchester, where long delays have been occurring.
The experiment began on Monday and is expected to last for about two weeks.
The two junction designs to be tried out are shown on the accompanying plan. The first will be a "mini-roundabout". In this layout the junction remains a single island roundabout but the central island has been considerably reduced in size compared with the existing one. The approaches have been extended into the junction to allow extra lanes to be added for traffic queuing behind the give-way lines. The capacity of the junction, it is claimed, is increased because more drivers are able to cross the give-way line to take advantage of gaps in circulating traffic. This layout uses ground occupied by the present large centralisland and creates more space where it is most needed — at
the entries.
The second layout is called a "ring junction". It incorporates four "miniroundabouts" and its operation depends on drivers giving way to traffic coming from their immediate right at each give-way line. Paths to be taken by drivers going straight on, or turning left or right, are shown by the dotted lines on the plan. In special circumstances, for example in the 'case of long vehicles, the intersection can also be treated as a normal roundabout, with vehicles turning left on entry and going around the outer ring to any exit.
The main advantages of this arrangement are said to be: (I) opposing right turns do not conflict with one another, and take the shortest path through the junction; (2) traffic streams are split up so that at each give-way line the crossing flows are lighter and it is easier to find a suitable gap.
The efficiency of these new junction designs will be tested during the summer when traffic flow is high.