Road design

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Appendix E Extended Design Domain (EDD) for Entry Path Radii

The maximum entry path radii in Section 4.5.3 are based on achieving a desired maximum entry speed for vehicles which will generally minimise crash rates. The following entry path radii are larger than those in Section 4.5.3 and may be acceptable to use where existing site constraints result in adoption of the NDD values being unachievable.

Table E 1: EDD maximum entry path radii for one and two-lane roundabouts

Desired driver speed on the leg prior to the roundabout (km/h)Maximum entry path radius (m)
Single-lane entries(1)
Two-lane entry – staying in correct lane(2)
Two-lane entry – cutting across lanes(3)
≤ 401001.9 x actual entry path radius when staying in correct lane(4)
50801.8 x actual entry path radius when staying in correct lane(4)
60701.6 x actual entry path radius when staying in correct lane(4)
70701.5 x actual entry path radius when staying in correct lane(4)
≥ 80≤ 551.5 x actual entry path radius when staying in correct lane(4)
  1. Construction of the entry path of a single-lane entry for roundabouts comprising one or two circulating lanes is given in Figure 4.5.
  2. Construction of the entry path of a two-lane entry – staying in the correct lane for a two-lane roundabout is given in Figure 4.6.
  3. Construction of the entry path of a two-lane entry – cutting across lanes for a two-lane roundabout is given in Figure 4.7.
  4. Radius of the entry path for drivers staying in the correct lane as determined in Figure 4.6.