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07 May 2011 - 08:17
Beware the Intermittent Showers
We have had the driest April for many years and are approaching the end of the first week in May. The gardens are starting to suffer and water authorities are starting to make noises about rationing water in the summer. But life goes on!
That’s the problem – everything becomes ‘same old – same old’ and never a thought is given to how infrastructure, like roads, are actually changing in a way that we don’t recognise, apart from extreme heat when they might melt a little.
It won’t be long when we welcome a burst of rain, but we are never prepared for the protracted situation which this so often causes.
In long spells of dryness, the roads accumulate substantial amounts of oil deposits, rubber and waste fuel. Whilst it’s dry this is not too much of a problem, but then introduce moisture and the situation changes dramatically. Oil/fuel and water do not mix, causing a tactile film to float on the surface of the moisture, which exasperates the problem of a tyre gaining traction to the road. This in turn affects directional control and braking.
It is in the first five minutes of a downpour that is the most crucial, creating conditions that are separate to those of standing water situations. The drains cannot begin to clear the oil and water mix until there is sufficient volume to reach the drains and cause a continual flow. What slows down this process is all the microscopic beads of rubber from vehicle tyres which gets into the pores of the tarmac preventing the flow to the drains. The volume of water has to get quite substantial to move this denser material, hence it sits there until this can happen.
Whilst this is all unfolding, vehicle traction is greatly reduced. Motorcyclists are vulnerable to the reduced visibility through ‘dirty’ spray and to the fact that any painted lines on the road are now more slippery through their glass and petroleum–based recipe. Manhole covers are treacherous to all. Windscreens start to suffer with a milky-like residue thrown up from vehicles in front. When wipers are applied, the entire vision is obliterated by visual distortion for probably two sweeps of the wipers. In this time scale the driver has just driven some considerable distance blind. Hence we come back to our ‘protracted’ situation.
It cannot be emphasised enough, that drivers have to adapt to the changing conditions and not simply drive to the conditions that existed when their journey started. Driving blind is a recipe for a pile-up! From the above information, perhaps you can understand that road situations never change suddenly, they are always in a state of flux – the pile–up was waiting to happen!
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