We’ve finally experienced some seasonal weather conditions here in the UK. Gone is the dizzying mildness of October and November, and with us are the sparkling frosts of December. There has even been some festive snow across Scotland and high ground in northern England, although not to the extent that the meteorological-maniac that is Exacta Weather, and its bedfellow riot that is the Daily Express, would have you believe (more on this another time).
As a meteorologist in an operational weather centre, a large proportion of my wintertime workload involves liaising closely with local authorities who are responsible for salting the road network during cold, icy nights. A significant proportion of the gritting forecasts in the UK, disseminated among the many hundreds of authorities and highways agencies across the country, are produced by the private weather sector. These are not your average run-of-the-mill media forecasts either. They are, instead, extremely detailed, hour-by-hour predictions of road temperatures, wind speeds, cloud cover, rainfall amounts, snowfall amounts, humidity, and so on. Gritting authorities receive these forecasts daily and plan their salting actions accordingly.
But it doesn’t stop there. As most people are snuggled-up in bed during cold winter nights, meteorologists are manning 24hr weather desks, closely monitoring road and weather conditions across the country. If a frost suddenly develops in one portion of a county, the relevant authority is notified and gritters can roar into action to deal with the hazard quickly.
Gritting, or salting as it should probably be referred to, is a very scientific process. When salt is applied to a road surface, any moisture on that road has its properties changed. Whereas water normally freezes on roads at zero degrees Celsius, salt lowers this freezing temperature. In other words, water could drop to -5C, -10C, or even lower, before freezing. The principle is simple but, in reality, it’s not quite that easy.
You see, each authority has hundreds, if not thousands, of miles of road network to treat. This normally includes major A-roads, dual-carriageways, and other important road infrastructure. This doesn’t however, include the tens of thousands of miles of back-roads. Why, might you ask, are some roads allowed to freeze? Well, every full grit of the primary road network (that excludes back-roads) costs councils, and therefore YOU through your taxes, thousands of quid a pop. You not only have the cost of the lorries, diesel and salt to think about, but also the man-hours.
Picture the scene, if you will, and see if your response defines you as ignorant or educated. You’re driving along and you notice that the road ahead is covered in frost. Which of the following runs through your mind?
A) They haven’t gritted the roads and my taxes are being wasted.
B) There’s frost on the road, I’d better adjust my speed and take responsibility for myself.
Alarmingly, if widespread comment in social media, in news reports, and through day-to-day overhearing of conversations are anything to go by, the overwhelming answer of many would be “A”. If a poor fellow crashes on an icy road, or if someone slips whilst walking to their car on a frosty morning it seems that, invariably, it must be someone else’s fault.
On enountering a frosty road, or a road that is covered in snow, the following comment is all-too-common and I hear it almost daily:
Now, leaving aside the issue that the road may not actually be on the treating network in the first place, one thing comes to mind when I hear these frequently-uttered condemnations.
A gritter is a single lorry. It travels at 30-40mph and may take a few seconds to pass your house. It only needs to drive past once, and then it’s gone. The only sure-fire way of knowing whether a gritter has driven past is to stand at the roadside, all night in freezing conditions, until you spot one. You would be expected to wave merrily at the driver as it passes, of course.
But how many people sit on gritter-watch 24hrs a day? It must be frustrating to be a gritter driver, dragged out of your bed at 4am, putting your life on the line to treat a dangerously icy road, only to hear your neighbours crowing about how “the gritters weren’t out last night”.
Rather than a function of whether someone has actually seen a gritter with their own eyes, I suspect the main conclusions people draw as to why they believe the gritting lorries stayed back at base, is because the road is covered in ice, frost or snow.
At the risk of turning this musing into a Sunday afternoon lecture, here are the facts you should know about road gritting and hazardous highways:
* Grit/salt is not magical, mystical dust that wafts waves of warmth across the road, preventing the formation of ice or frost. It’s very helpful but not a complete solution.
* On roads that are sparsely-trafficked, ice, frost and snow will settle even if the road has been heavily gritted. Car movements will mix together the wintry hazard with the salt, allowing that hazard to melt but, without traffic, this process can’t occur and the frost or snow can literally sit on top of the salt.
* Salt has to be liberally scattered across a road surface. You’d complain about dirty cars and cracked windscreens if it was dumped by the tonne outside your house. Don’t assume every square inch of tarmac is free of ice as there’ll be areas that salt hasn’t managed to spread.
* When snow falls heavily, the rate of settling normally outstrips the rate of melting caused by salt. Therefore, a road covered in snow has probably been gritted but it will take time for that grit to work (and again, traffic speeds this up).
Just to repeat that last one, snow will settle on gritted roads. It’ll make me feel better if only one person reads that last bit!
The public misunderstanding of winter road gritting is not an excuse for its ignorance. There is a pandemic of science-scepticism across the world today and much of this is borne-out from people with little knowledge of a subject, having strong views on what they believe to be right. The simple act of winter road maintenance is at the sharp end of huge ignorance, fanned by a pathetic tabloid press, and forecasters, councils and gritting authorities are dealing with unprecedented, ill-informed complaints.
Ultimately, if it’s cold and frosty outside, drive to the conditions. Don’t assume roads have been gritted but, equally, don’t assume a road covered in ice or snow, hasn’t been.