Page 118 - Lecture Notes DCC3113

8.2.4 The characteristics and the types of roundabout

Roundabouts

A roundabout is a type of circular intersection or junction
in which road traffic flows almost continuously in one
direction around a central island

Figure 8-13: Roundabouts
Characteristics of Roundabouts

 Suitable for 3 to 5 or more junction, have almost similar flow, no intersect flow
 Non-serious accident do occur, but less than two third compare to signalized junction
 Needed large area, non-warranty of pedestrian safety
 If has high volume, roundabout will be locked
 Not easily updated as traffic signal
 Require a lot of traffic sign, central island must be lighted during night time, can be landscape to
reduce night

Advantages of roundabout Disadvantages of roundabout
 Circle requires a wide flat area
 Safety  Pedestrian safety is not guaranteed
 Improved traffic flow  The circle will not easily be amended or
 Better solution for complex intersections modified
 Fewer conflict points  If traffic volume is too high, the circle will
be “locked” and causes a long delay

Types of roundabouts

 Conventional roundabout, Dc > 25m , Di > 50

Figure 8-14: Conventional roundabout

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