[talk-au] traffic lights on dual carriageway intersections

John Henderson snowgum at gmx.com
Sat Nov 3 07:03:28 GMT 2012


"Steer" wrote:

> I have been trying to find the accepted practise for mapping traffic
> lights where dual carriageways interest.  There is much discussion
> on various sites, but most seems to be a bit old, and I’m not
> convinced I’ve found what is the latest accepted practise.

> I checked some intersections in Melbourne’s CBD, and the method I saw
> that I liked and thought the best was where there were 4 lights at
> the intersection, but they were not placed on the intersecting modes,
> but one node back “upstream” on each way.  I think this is good
> because no matter which way you go through the intersection, you only
> pass one set of lights (rather than 2 if they were placed on the
> actual intersecting nodes).

> Any comments?

I have always entered such traffic lights on dual carriageways in the
way you describe.  This is because:

1. The "traffic light count" along a section of road is then accurate, and

2.  It's the accurate representation of what's on the ground.  It lets
us convey the significance of the stop lines associated with the lights.
That's something we can't do with two-way traffic without compromising
point 1.

I have argued this position on previous occasions.

John



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