04 Jul 2018
Posted by Chris Jones 
Miracles do happen. Very rarely, the Irish rugby team win a series in Australia, or England’s footballers win a penalty shoot-out. Even more rarely, you get a summer heatwave in Ireland.
It is a wonder and we should all enjoy it while we can, but it does bring its own problems on the roads – not least of which is the problem of road surfaces actually melting in the heat.
A few years ago in the UK, a section of the M25 – London’s equivalent to the M50 – had to be closed because the surface was unsafe. Predictably it caused chaos. Closer to home, we have had reports into AA Roadwatch over the last couple of weeks of road surfaces becoming extremely dangerous, and some roads have had to close.
It may seem crazy that our roads can let us down like this. It has been hot of course but there are roads in warmer countries that get this all the time without disintegrating and motorists have been asking us how on earth it could happen.
It is a bit like the reverse of the problem that we had during the Storm Emma earlier in the year. Irish roads, especially secondary roads, took damage that is still not fully repaired. Again, those low temperatures do not cause problems in Norway so why here?
The answer is that roads are built within ‘normal’ design parameters that will vary from country to country. Ours have to deal with much more rainfall but much less heat than a road in Nevada for example.
We hit 32 degrees recently but it only gets that hot for a few days every 20 years if we are lucky. You can build roads that can cope with those temperatures using special polymers and binding agents in the top layer of tarmac but it is expensive.
It is not really possible or sensible to over-engineer a road to such an extent that huge cost is incurred making it proof against problems that might not arise more than two or three times in a century.
The road surface itself can be as much as 20 degrees hotter than the air temperature which is normally measured in the shade and above the ground. If you are curious you can have a look at the road temperatures map on the TII website. Their excellent system of thermal mapping was put in place with winter ice and gritting in mind, but we have seen temperatures nearing 50 degrees in the heatwave.
When it gets as hot as that the tar on a road will start to behave like molasses. As traffic uses it the road will start to develop ridges and ruts like a mud track. For the unsuspecting driver, this means that you can hit a bad patch without warning. Braking and steering will be affected, and for those on motorbikes it is extremely dangerous.
In some areas, roads have been treated with grit or gravel. For the driver, the safety advice is something that we are all familiar with: slow down. Reducing speed and staying clear of the car in front is the only effective counter-measure, and any problem will be magnified if you are driving too fast.
Finally, another word of warning. In the Mediterranean heatwave of 2012, a huge forest fire took hold on the French/Spanish border north of Barcelona. 32,000 acres were destroyed, four people died and 100 were injured. The hugely busy AP7 motorway was essentially destroyed.
It is suspected that the disaster could well have been caused by a driver flicking a cigarette from the car window. With Ireland currently under a status red fire alert and our emergency services already dealing with fires across the country, now is the time to be extra cautious.
