Intersection Spacing – Survey
RedSquare Traffic’s team performed a turning movement survey at the above intersection. We saw a near miss crash that could have resulted in a fatality or a serious injury. A car approaching from northwest successfully avoided a potential rear-end crash at Outlet Road. However, it had to avoid another conflict at the gravel road further southeast (Coghlans Road).
We couldn’t help but notice the below par spacing of the two intersections (Outlet Road and Coghlans Road). Currently at 109.7m, where it should ideally be 275m in a rural 100km/h zone. The 275m space is known as the functional area of an intersection. It goes without saying, the geometry of the other legs of this intersection only makes this intersection a complex one, in a rural context.
Austroads Guide to Road Design
Austroads Guide to Road Design Part 4 defines this situation as:
“Stopping distance is a method of assessing the required downstream distance. This allows a driver to pass through the intersection before having to decide that it is necessary to stop because of a conflict at a downstream access connection“.
It is true – in a rural context, it may not always be necessary to provide the distances specified on the standards and regulations. Especially, due to the low turning traffic volumes. However, it is always in a scenario like this that crashes are likely to happen. Drivers have low expectations of turning vehicles. Lack of street lighting only make it worse.
Intersection Spacing Solution
A common traffic engineering solution is to provide a basic auxiliary right turn (BAR) treatment. Alternatively, a widened shoulder could be provided. This would allow for a vehicle to get around a stopped/stopping vehicle without causing a rear-end crash. This also increases space available for an emergency manoeuvre to avoid unexpected conflicts at an intersection.
Keep your eyes on the road. It only takes a millisecond for something terrible to happen.
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