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Comment by kingpiss | Hacker News Reader

I live in a warm place so I am out of touch, but isn't that like a lot of gritters for how small Scotland is?

Hailing from Canada - does not look like nearly enough, probably because Scotland has relatively mild climate.

The road network is very dense and branched out. Also, it takes several snow plowing machines going in formation to clean major multi lane highway. Timing is also important- you want the road cleaned as soon as possible not several days later, especially if wet snow freezes into ice.

The trunk road network is 2179 miles (3506km) long and there's ~120 gritters deployed.

Doesn't seem like an unreasonable amount to me.

2179/120 means each one has to cover about 18 miles. Assuming they average 36 mph, assuming each trunk road is 2 lanes in both directions (assuming one pass per lane and not including time to clean up the shoulder/median), and assuming they spend 50% of their time gritting/plowing new roads rather than filling up/changing drivers/driving on plowed roads to get to or from their target road, that's one pass every four hours. Seems quite reasonable (if a bit undersized) to me as a Michigander.

We're having unseasonably warm weather here - it's 45 and sunny instead of a typical 25 and overcast - so all the snow has melted in Southwest Michigan and our state plow tracking map is basically blank today:

https://mdotjboss.state.mi.us/MiDrive/map

We have about 800 snowplows to cover 12,000 miles of state/trunk roads (15 miles per vehicle). It requires about 2,000 operators to keep those 800 plow trucks running 24x7 when it's really snowing.

> assuming each trunk road is 2 lanes in both directions

At a rough guess, about half of the roads have 2 lanes in each direction, and the rest one lane in each direction.

That should improve your estimate.

My Dad used to be a council civil engineer - every year he took turns deciding when to send the gritters out. There’s quite an art to deciding on a plan based on the road dew points, the precipitation forecast and the temperature. Precipitation washes the salt off - so that mileage often has to be covered multiple times over.

He used to get very nerdy over Christmas checking the road network data website :)

Remember most of these "major" routes are single track A road at best, apart from our small motorway network. Once you are north of the central belt, where Glasgow and Edinburgh are, your main road can be anything but. This means they don't cover as much ground as you might expect, hence we do need quite a few of them. https://trafficscotland.org/livetrafficcameras/

Single Track means there is just one vehicle width shared both directions, if you meet someone coming the opposite way too bad, the next size up is Single Track with Passing Places (at intervals the road is wide enough for vehicles to pass in opposite directions). Not many Single Track A roads left in Britain, the A roads have mostly been upgraded even in Scotland. You're likely thinking of single Carriageway, which means there's only one road surface but it has separate lanes in each direction. Lots of those.

As I note in another comment - the gritters on that map are a small subset of all the gritters - those are just the ones that appear to be centrally controlled on 'major' routes.

We don't get huge amounts of snow (at least not very often) - but what we do get is a combination of snow and high winds - which can make it a nightmare to keep higher roads open.

Do you get icy-freeze-thaw conditions? Here in DC, we don't get a ton of snow, but when we do get winter weather, it's always just at freezing, so everything immediately gets thawed and re-frozen into ice. Most of my trips to Scotland have been summer, so only had snow up Glen Shee. The one time I visited in winter, it snowed a bit as I drove between Laggan and Dunkeld, but nothing dangerous.

"Glen Shee" - Scotland's version of the French Three Valleys! :-)

Not sure we get any kind of weather conditions (apart from wind and rain) with any predictability!

Ha! My parents are from Blairgowrie, so I've been through there often, but never to ski. Beautiful area any time of year. Apparently the Glen Shee road used to be a lot narrower, steeper, and twistier, and they sometimes had to reverse up one of the grades (reverse gear was lower than 1st in Dad's first car, a Hillman Imp, IIRC).

The twisty bit was called the Devil's Elbow [1], I remember going over it as a child before the modern road bypassed it. My parent's first car was a Hillman Imp too, I used to sleep on the shelf over the rear engine for part of trips up to Aberdeen.

I have had to fit chains to my car to get over the Cairnwell Pass, nothing passed me while I was fitting them and I could see people turning around lower down the hill, didn't see any gritters.

[1] https://en.wikipedia.org/wiki/Cairnwell_Pass

icy-freeze-thaw is perfect for ski resorts, but sadly it's rare that it happens. It rarely happens in the lowlands where most of Scotland's population lives. We do get frosts in the morning, but it's quite rare for sub-zero C temperatures thanks to our lovely Atlantic-influenced maritime climate. Never that cold in winter, never that warm (sadly) in summer.

Which can be much harder to keep clear. Here in Minnesota, USA we get both large amounts of snow and high winds. It's not unusual to have whiteout blizzard conditions and MNDot (Department of Transportation) warning against any travel in some parts of the state..

They can clear a road only to have the wind cover it with snow again an hour later.

I live on top of a hill so I'm well acquainted with what happens when winds gust to 40mph after Mother Nature has dumped 6" of snow on us. Wind-packed snowdrifts suck ass!

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