An-Ice question

[dextrous63]

When carts, tractors, cars etc drive one after the other over grass, they leave a track consisting of two worn parallel lines, with untouched grass between and beyond this lines/ruts.

The question I have is...why do busy-ish roads have no ice on them rather than parallel lines?  

[Alex]

Can I phone a friend ?

[Scrumpy]

🔔 📞 📞
  ' Um ! umm !! Sorry Alex.. I don't know.. Best ask the audience '

[klondike]

The question I have is...why do busy-ish roads have no ice on them rather than parallel lines? 

Because the council grit them?

[dextrous63]

Because the council grit them?

Highly unlikely.  But even if they did, the grit wouldn't melt the entire surface, surely,

[Alex]

🔔 📞 📞
  ' Um ! umm !! Sorry Alex.. I don't know.. Best ask the audience '

Audience said different sized vehicles ?

[klondike]

Highly unlikely.  But even if they did, the grit wouldn't melt the entire surface, surely,

The grit is partly salt crystals. The salt dissolves and raises the freezing point of a small amount of water and that spreads by itself and on car tyres and melts even more frost. Before too long the entire surface gets covered with salty water which is above the freezing point of salty water.

Have you never scattered salt on a frozen path? It isn't necessary to carefully cover the entire path with salt. It melts the frost and spreads itself.

[dextrous63]

Audience said different sized vehicles ?

Possible, and that would explain wider ruts in the snow.  Still can't see how that'd clear the entire surface though.🤷🏻�♂️

The grit is partly salt crystals. The salt dissolves and raises the freezing point of a small amount of water and that spreads by itself and on car tyres and melts even more frost. Before too long the entire surface gets covered with salty water which is above the freezing point of salty water.

Have you never scattered salt on a frozen path? It isn't necessary to carefully cover the entire path with salt. It melts the frost and spreads itself.

That makes more sense, thanks.  In the absence of any other reason, other than huge amounts of underfloor heating going on🤣🤣🤣, I'll settle for that.  Just seems amazing how such a relatively tiny amount of salt can create sufficient quantities of saline of an appropriate strength.

[Mups]

When carts, tractors, cars etc drive one after the other over grass, they leave a track consisting of two worn parallel lines, with untouched grass between and beyond this lines/ruts.

The question I have is...why do busy-ish roads have no ice on them rather than parallel lines? 

Because there are many more cars on the roads than tractors on grass.  And thousands of cars don't all follow exactly in the previous ones tyre marks, so the ice melts the width of the road in the end.

Also, as Klondike said,  don't forget the gritters.  They don't do much gritting on grass, so the frost stays put. 

[klondike]

TBH it isn't something that I've given much thought to but there isn't a huge amount of water in a layer of frost or snow come to that as a lot of it is mostly air. Add to that the pressure under car tyres is going to produce a bit of heat too.

[dextrous63]

There are a couple of threads about the recent cold weather, but I'll put my comment here if that's ok.

Have any of you spotted the alarming number of drivers who don't seem to understand that cold, icy roads require more care and attention than usual,

[Ashy]

I'd venture to suggest that the vehicle, particularly the engine, warms the space between the wheels. The wheels themselves would only crush the snow into that thick sort of cake icing but to melt it requires warmth. 

[klondike]

With enough traffic they'll warm the air a little but I think they pass over too quickly to melt ice. The reason main roads are clear of frost is gritting which lowers the freezing point of water. Look at side roads - they stay frosty apart from maybe wheel tracks until there is a thaw.

[JBR]

Fortunately, most of the snow and ice around here has melted (though I don't know about Scotland).

Next, the floods come!