Originally Posted by cyccommute

No and I resent the implication. Nothing I have said is inflammatory nor off-topic nor extraneous. The math and chemistry I've presented is very germane to the discussion and fairly simple stuff...high school chemistry would cover it.



I've read that article and it's not convincing. The salient quote is this



Some guy on the internet isn't a credible source. Doing a google search, I can find all kinds of pages with almost the same sentence as the first sentence. But I can't find a single journal article on the topic.

And the above certainly doesn't fit with the quote from Wikipedia



At that temperature there are lots of other, more reasonable mechanisms for ice formation.



But it takes more water than you have even from many cars. I do agree with the straight dope guy about one thing, water is going to condense in the tailpipe and dribble out. You can see it from just about any tailpipe of any car. But as he said, the water is going to freeze in a blob and it will likely be outside the tire track which won't cause problems.

But if you condense water in the tailpipe, it's not helping the "freezing car exhaust fog" argument. You would need water vapor to freeze on the road surface in a uniform layer. For a typical stoplight duration and the burn rate of gasoline, you only have 9 g of water to work with. Since you aren't Canadian, I'll convert...that's a bit under 2 teaspoons. If you remove half of the water due to condensation...not a bad estimate but only a guess...you have 5 g (1 tsp) of water to work with. Let's say you have a 3 lane road with 5 cars in each lane. That's 15 cars or 75 ml (15 tsp or about 1/3 cup) to work with.

But goes into the volume that those 15 cars are contained in. That volume is, roughly, 504 cubic meters. 75 g of water (density of 1g/ml) spread throughout that volume would give you 0.15g/cubic meter. If the air isn't saturated it will absorb the water from the tailpipe easily. Minneapolis is currently (like right now) at 75% RH. That means that each cubic meter of air contains 75% of the possible 1.0g of water it can carry at your current temperature (just about 0°F) or 0.75g/cubic meter. Adding 0.15g/cubic meter of water won't cause water to precipitate out. Perhaps a very tiny amount will but not enough to cause the roads to ice.

Ice may have formed overnight but the cars would just polish that ice resulting in a slicker intersection.

Originally Posted by Hypno Toad