Divided road turns

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This page is a response to Letters to the Editor (NT News, August 2004) where correspondents discussed the method(s) of positioning in the centre gap of a divided road when turning right or performing a U-turn. The intersection of Stuart Hwy & Duke St in Stuart Park which prompted the correspondence has since been rearranged and a problem there no longer exists at that particular spot.


Cross roads - the old way...

The basic method of turning has changed since I learned to drive in 1966.
Back then, vehicles passed behind each other when turning right resulting in their paths crossing twice. A stainless steel dome in the centre of the intersection - a "silent cop" - served as a turn marker. From memory, this method was referred to as a "diamond turn".
The last time I was in Nhulubuy, a T-intersection had a silent cop, obviously placed to discourage vehicles cutting the corner when turning into the terminating road.

Cross roads - the new way...

Australian Road Rule 33(3) states "If there is no road marking indicating how the turn is required to be made, the driver must make the turn so the driver passes as near as practicable to the right of the centre of the intersection". The accompanying diagram depicts a turn similar to the one shown at left.
I have heard of this type of turn referred to as "diagonal turns".

The Australian Road Rules are written in clear English, not legalese as in the Acts & Regulations. While this makes them easier to understand it also makes them open to interpretation in some cases. And in this case, the Rules don't help by omitting detail on how right-turns are to be made at divided roads.

A decision on how to perform a turn depends on one or more factors - whether it is a crossover road or a safety gap, whether there is an island or a "silent cop" in the middle, whether there is a continuation line to guide the turn, and how the ends of the median strip are shaped. In the absence of guiding islands or lines there are two ways of doing a turn:
  1. "Method 1" below follows the modern diagonal turn principle. The shaping of the median-strip ends (rounded, not squared-off as in a crossover road) suggests that this is how the turns are intended to be made. I have not yet sought advice from a traffic engineer on this.
    U-turns - the text of Australian Road Rule 42(a) only describes how to start a U-turn at a median strip (i.e. from the right-hand lane) but the accompanying diagram depicts a vehicle doing a U-turn by turning short around the end of the island.

  2. "Method 2" follows the diamond turn principle and is less widely used, which could be reason enough not to use it at all.
    Also, this method causes serious problems at narrow islands where vehicles cannot fit completely inside the limits of the gap while waiting to complete the turn.
Which method to use?
Method 1 has more going for it and the Australian Road Rules seem to favour it via illustration if not in words.
This and the fact that most drivers use it makes it the better option in my opinion. It also seems to be the method favoured by most driving instructors. However drivers about to enter a median strip gap should be prepared to use the second option if the position of a vehicle already in the gap makes it necessary to do so.

(In all diagrams below, the red cars give way to the blue & yellow cars)

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  "Safety Gap" type of intersection


NARROW GAP - Method 1

NARROW GAP - Method 2
(The cars in the centre are forcing the yellow car to go wide
Not desirable!).

WIDE GAP - Method 1

WIDE GAP - Method 2
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"Crossover Road" type of intersection


Crossover Road Intersection Some intersections have a painted or raised island or a dividing line to indicate that the centre gap is actually a crossover road.

Unless signs indicate otherwise, vehicles keep to the left of these islands. The correct way to turn in this situation is shown at left.

One exception I know of is the Woods St / Daly St cross-roads intersection in the Darwin CBD which has no centre island, but a broken continuation line guides drivers turning right from Woods St into Daly street to position to the right, similar to the turn done by the red cars in "Method 1" above.
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