MAP TYPE SIGNS FOR IRREGULARLY SHAPED ROUNDABOUTS AND GYRATORY SYSTEMS
5.51 Figure 5-31 gives examples of map type signs for junctions where the normal roundabout symbol does not reflect the actual road layout. For gyratory systems it is usually more appropriate to use a symbol width relating to the status of the route through the junction, rather than the special width of 5sw. For irregularly shaped roundabouts the symbol width of 5sw will be appropriate in most cases.
5.52 A special type of roundabout is the dumb-bell. This is where two adjacent roundabouts are joined to form a gyratory system. They are likely to be used where (a) a bridge between the two roundabouts precludes the construction of a single large roundabout (some grade separated junctions are purposely designed like this to economise on the provision of structures), or (b) traffic congestion between two roundabouts can be eased by the formation of a gyratory system.
5.53 The design of the map type symbols for dumb-bell roundabouts is shown in figure 5-32. Where the route is through the two partial roundabouts, the complete road layout is shown. However, in the case of an exit slip road at a grade separated junction where there are limited turning movements (i.e. a single left turn and a single right turn) a simplified symbol, as shown in figure 5-32, may be used. It should be noted that for this simplified symbol the width of the right turn route arm is 5sw, irrespective of the status of the route. Simplified symbols, showing only the first part of the junction, may also be used where an advance direction sign is provided between the two partial roundabouts.
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