A spreader meters what it puts down, grams per square metre, against the road width and the distance driven. Route 9 comes back a tonne light on a run that should use four, every time, and the road behind it is bare.
I have driven a gritter for the council for sixteen winters.
The dosing is the whole job and it is not a man with a shovel.
The spreader is on the back of the lorry with a hopper, an auger and a spinning disc. It is controlled by a box in the cab that knows the road speed from the lorry, so the rate stays constant whatever I do with the pedal. I set grams per square metre and a spread width and it does the rest.
The forecast decides the rate. Ten grams for a light frost, twenty for a hard one, forty with snow expected. It comes off the ice prediction system and it is in the treatment order I am given at the start of the run.
And it logs. Every run records the route, the start and finish, the rate, the distance, and the tonnage out of the hopper, and that is what gets reconciled against the salt barn.
Route 9 is a rural loop, forty one kilometres, mostly B road with a stretch of unclassified at the top end.
At twenty grams a square metre over forty one kilometres of six metre road, the arithmetic is about five tonnes. Call it four and a half with the bits I do not treat.
Route 9 uses five and a half to six.
That is not a rounding error, and it is not me being heavy handed, because I am not the only one who drives it.
Four of us are on that route across a winter and all four come back the same. I have looked at the logs, which anybody in the depot can, because they go up on the wall.
Where the extra goes.
Between the eighteenth and the twenty first kilometre there is a stretch of about three kilometres along the bottom of a valley, past a wood on one side and a beck on the other.
The hopper empties faster there. You can see it on the gauge if you are watching, and I have watched it many times.
Same rate on the box. Same speed. Same width. And the load goes down about twice as fast for three kilometres and then goes back to normal.
What has been done to the machine.
The spreader was calibrated at the start of every season, which is standard, by putting a sheet down and weighing what lands on it.
It was rebuilt in 2021: new auger, new disc, new control box, because I had made enough noise about it.
The first run after the rebuild used five and three quarter tonnes.
We swapped lorries. Route 9 in lorry 4 instead of lorry 2. Same. Lorry 2 on route 7 uses exactly what route 7 should use.
It is the road, not the machine, and I have known that for about eleven years.
The road.
It is what stops this being a story about a broken spreader.
That three kilometres is bare afterwards. Not treated, bare: black and dry when everything either side of it is white with salt scatter you can see in the headlights.
Salt works by lowering the freezing point of water on the surface, and after a run you can see the crystals lying in the wheel tracks for hours. I have driven that stretch again on the same night, an hour later, on the way back from a top up, and there is nothing on it.
No salt on the surface and no ice on the surface either. The road is dry.
The temperature.
Every gritter has a road surface thermometer, which is an infrared sensor under the cab reading the tarmac in front of the wheel. It goes in the log with everything else.
On that three kilometres the road surface reads between one and a half and two degrees below the sections either side of it.
The air temperature does not change. The road does.
That is a real and known thing on a road: a valley bottom is a frost hollow and cold air drains into it. It is exactly why route 9 exists and why it is treated when the town is not.
What is not known is a frost hollow that takes twice the salt and comes out dry.
What I have raised, and how it ended.
I have put it in writing three times over eleven years. The first two went nowhere in the ordinary way of things going nowhere.
The third, in 2019, got me a meeting with somebody from the winter service team, who was thorough and pleasant and who came out with me on a run.
He watched the gauge. He read the log. He said the rate was correct, the machine was working, and the treatment was effective, and asked me what outcome I was looking for.
That question stopped me, because the honest answer is that route 9 has never had an accident on that stretch in sixteen years, in a valley bottom that ought to be the worst three kilometres in the district.
It is the safest bit of road I treat.
So the salt goes in the budget as it always has, about a tonne a run more than the arithmetic wants, on a route that is run maybe thirty times a winter, and nobody has ever queried it because a wet winter costs the council a hundred times that in overtime.
And I do the run, and I watch the gauge go down at the eighteenth kilometre the way it has since 2009.
The only thing I have changed is that I no longer stop at the lay-by at the twentieth to check the load, which I used to, because it is halfway and it is the natural place.
I go straight through now, and I do the check at the top of the hill in the open, where you can see the lights of the town.