Black ice: the invisible enemy
#151
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Any experienced winter cyclist should expect black ice, it common sense that winter will produce black ice when you least expect it. Even if you don't see the black ice at least take some precautions and be prepared for it. Don't slam your brakes hard at the last second and don't take corners at crazy insane speeds when there is a risk of black ice or when the road conditions are slick.
#152
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A while back we had a sunny weekend of above freezing which melted some snow and created some runoff. Then we had a night of sub freezing temperature. When we got up Monday morning, my driveway was all iced up. Not thick, not white, just a very thin layer of ice that you can't see and that was impossible to walk on without taking very small steps.
But riding was no problem at all just as long as you anticipate ahead to make sure you are braking moderately.
But riding was no problem at all just as long as you anticipate ahead to make sure you are braking moderately.
You can ride icy conditions with good tires (studded). I have years of experience riding through the winter in Minneapolis, I see tons of ice, snow, cold, etc. I'm happy to help and share my experience, but sorry, I need to be done with this endless conversation about which kinda ice is which ice. It's pointless and tiresome.
#153
Bicycle Repair Man !!!
When you are dealing with a vehicle's weight and momentum any ice is a bad thing, a bicycle with studded tyres has a fairly high contact pressure, lower mass, and a fairly low rpm engine and can get much better traction than a vehicle in really icy conditions.
#154
Senior Member
You are talking about re-freeze. I'm talking about the ice that forms from the auto exhaust in sub-zero (F) temps. See my YouTube clip back on page 3, that was refreeze, not black ice. All forms of ice have the same effect on road surfaces (refreeze or black ice or ice ice), it make is slippery. ....
"Black" a generic term used to describe either the unknown or non-visible: Black Hole (light can't escape), dark matter, dark energy (unknown matter or energy causing un-explained behaviour of the universe), black box (a device where data goes in and information comes out).
#155
contiuniously variable
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Black ice here forms from melting snow in sunlight then the sun sets. It doesn't really get cold enough for vapor to freeze here, though it can happen on bridges (hence the signs).
- Andy
- Andy
#156
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Whether the exhaust is directed down or not, a lot of it comes in contact with the pavement. It doesn't all "rise up out of the pipe very rapidly", - probably because it's condensing. If you've been on the streets in very cold weather you will see it and my guess is that it's more than you realized. Enough to cause problems over the course of a rush hour.
Now let's stuff 44,000 cars into that volume. Let's make each one burn 1 gallon of gasoline. That 167,000 kg of water that those 44,000 cars put out. The cars contribute 0.25% of the total water in the air. It's, almost literally, a drop in the bucket.
Now let's look at the ice that could form over that 30 km area. Let's assume 3 mm so that the ice is actually completely covering the craggy surface of the pavement. I'm also going to assume that the entire area is covered with 3mm of ice including all horizontal surfaces of the buildings. The total volume of a 900,000,000 square m x 3mm object is 270,000,000 mL. Water weighs in at just around 1g per mL which means that you have 270,000 kg of ice covering the area. You are about 100,000 kg short of the amount of water you need if every single car combusts one gallon of gas. And you'd have to wring every drop out of the exhaust.
There's an ocean of moisture laden air above the cars and even the 270,000 kg of ice is but a drop in that ocean. What I contest is the statement that car exhaust is the major contributor. It's a minor contributor at best.
[QUOTE=tjspiel;17587939]
For ice to form you need water, - which has to come from someplace. Black ice as I'm describing it is typically found at intersections on dry, very cold days. Again, I'm not talking about bridges. Where does the water come from? Why intersections more than anyplace else? What do you suppose is happening to the water coming into contact with the pavement in the picture above?
Black ice is just clear ice, with a somewhat shiny surface, over a black undersurface such as the road or other pavement. Doesn't really matter where it came from, a car tailpipe, refrozen runoff, freezing fog or drizzle. It can be hard to see, but it is not invisible. I encounter the stuff all the time, and have never fallen as a result, because I can see it. It's not actually invisible.
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#157
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If it's ice you can't see, it's black ice regardless of how it's formed.
"Black" a generic term used to describe either the unknown or non-visible: Black Hole (light can't escape), dark matter, dark energy (unknown matter or energy causing un-explained behaviour of the universe), black box (a device where data goes in and information comes out).
"Black" a generic term used to describe either the unknown or non-visible: Black Hole (light can't escape), dark matter, dark energy (unknown matter or energy causing un-explained behaviour of the universe), black box (a device where data goes in and information comes out).
Re-freeze happens with temps are near freezing, snow melts and refreeze in shady areas (i.e. under bridges)
Black ice happens when temps are below 0F, ice forms from auto exhaust of idling cars (i.e. stop lights)
This is helpful the next time you are talking with a Minnesotan, doncha know, like we have hotdishes, drink pop, and kids play "duck, duck, grey duck".
#158
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At low temperatures (below –18 °C), black ice can form on roadways when the moisture from automobile exhaust condenses on the road surface.[SUP][4][/SUP] Such conditions caused multiple accidents in Minnesota when the temperatures dipped below –18 °C for a prolonged period of time in mid-December 2008.[SUP][5][/SUP] Salt's ineffectiveness at melting ice at these temperatures compounds the problem.
#159
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You guys think black ice is bad? Sheesh, that's nothing. Try hitting Vanilla Ice on your bike. Not even foot retention will help you!
#160
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Yes, lots of bridges ice without being over water but it's not "car exhaust"
Yes, some water from car exhaust will condense out but it's a minor component. Let's say you have a city that is 30 km square (19 miles). Now, go up 60 m (200 ft), that a volume of 5.4 x10^10 cubic meters. Let's assume that the air is at-18°C (0°F). It can carry 1.2 g per cubic meter or the total amount of water available is 64,800,000 kg assuming complete saturation of the air.
Now let's stuff 44,000 cars into that volume. Let's make each one burn 1 gallon of gasoline. That 167,000 kg of water that those 44,000 cars put out. The cars contribute 0.25% of the total water in the air. It's, almost literally, a drop in the bucket.
Now let's look at the ice that could form over that 30 km area. Let's assume 3 mm so that the ice is actually completely covering the craggy surface of the pavement. I'm also going to assume that the entire area is covered with 3mm of ice including all horizontal surfaces of the buildings. The total volume of a 900,000,000 square m x 3mm object is 270,000,000 mL. Water weighs in at just around 1g per mL which means that you have 270,000 kg of ice covering the area. You are about 100,000 kg short of the amount of water you need if every single car combusts one gallon of gas. And you'd have to wring every drop out of the exhaust.
Yes, some water from car exhaust will condense out but it's a minor component. Let's say you have a city that is 30 km square (19 miles). Now, go up 60 m (200 ft), that a volume of 5.4 x10^10 cubic meters. Let's assume that the air is at-18°C (0°F). It can carry 1.2 g per cubic meter or the total amount of water available is 64,800,000 kg assuming complete saturation of the air.
Now let's stuff 44,000 cars into that volume. Let's make each one burn 1 gallon of gasoline. That 167,000 kg of water that those 44,000 cars put out. The cars contribute 0.25% of the total water in the air. It's, almost literally, a drop in the bucket.
Now let's look at the ice that could form over that 30 km area. Let's assume 3 mm so that the ice is actually completely covering the craggy surface of the pavement. I'm also going to assume that the entire area is covered with 3mm of ice including all horizontal surfaces of the buildings. The total volume of a 900,000,000 square m x 3mm object is 270,000,000 mL. Water weighs in at just around 1g per mL which means that you have 270,000 kg of ice covering the area. You are about 100,000 kg short of the amount of water you need if every single car combusts one gallon of gas. And you'd have to wring every drop out of the exhaust.
And because it's localized and not covering everything, it is more dangerous because it's unexpected.
I should have left the whole topic of bridges alone because while they do ice up quicker, I agree that it's not usually from car exhaust but typically melted snow/ice, fog, or whatever. You can get black ice from exhaust on them as well if traffic is backed up and sitting there (and it's really cold) but usually when we get warnings about slippery bridges it's when temps drop below freezing after warmer days.
Last edited by tjspiel; 02-27-15 at 10:10 AM.
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Discovery Channel. So much promise, so little delivery.
We clever little monkeys like to make machines and be busy so we make roads. Then we cover them with a black tar residue that we can't find anything else to do with and the ice precipitates out on those surfaces. We can't see the ice on top because it is still transparent but the underlying surface is black. So we call it "black" ice. The ice isn't "black" anymore than it is "white" when it is not on the road.
Black ice is a real phenomenon and not some myth although half of the people in North America will probably never experience it... some interesting stats are that the stopping distance on ice is 9 times that of dry pavement and the warmer and and closer to freezing, the more slippery ice gets. We need to get into analyzing ice at a molecular level to figure that out.
Last night the temperature dropped to -18C and I knew what to expect on my morning drive... the intersections are sanded and traction is improved but that zone behind the busiest intersections gets as slippery as a road can get (if you are driving).
This is where cars wait in a cloud of condensing exhaust.
This is where cars wait in a cloud of condensing exhaust.
Again, it's not the car exhaust that causes the ice nor the intersections to be more slippery. There's just not enough water in the car exhaust at an intersection to cause the problem. If each car sat at the intersection and burn and entire gallon of gas, maybe, but that isn't what happens. A car burns around 0.1 gallons per hour idling. A car waiting for 2 minutes for a typical stoplight would burn 0.003 gallons or about 7g of gas. Through the magic of chemistry, I know that 9g of water is going to be produced per car. That's a minuscule amount of water.
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#162
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Vanilla Ice on Burglary Arrest: "It's a Mess; I'm Dealing With It" - Hollywood Reporter
#163
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Again, it's not the car exhaust that causes the ice nor the intersections to be more slippery. There's just not enough water in the car exhaust at an intersection to cause the problem. If each car sat at the intersection and burn and entire gallon of gas, maybe, but that isn't what happens. A car burns around 0.1 gallons per hour idling. A car waiting for 2 minutes for a typical stoplight would burn 0.003 gallons or about 7g of gas. Through the magic of chemistry, I know that 9g of water is going to be produced per car. That's a minuscule amount of water.
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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.
In places where cars idle (such as driveways, toll plazas, and intersections), automobile exhaust can be an important contributor. At cold temperatures, auto exhaust (like your breath) contains a visible fog of water droplets, formed when invisible water vapor condenses into droplets. Some of these fog droplets may then freeze when they come in contact with the roadway within a few feet of the tailpipe. More water condenses on the inside surface of the tailpipe and drips out, leaving a thicker but more localized patch of ice directly beneath it.
And the above certainly doesn't fit with the quote from Wikipedia
At low temperatures (below –18 °C), black ice can form on roadways when the moisture from automobile exhaust condenses on the road surface.[4]
Wait, wait, hold on. I'm not saying that ice formed from car exhaust completely covers the city. Black ice from car exhaust is very localized, - typically at intersections or areas where you have many cars stopped for periods of time or moving slowly. It doesn't take that much water.
And because it's localized and not covering everything, it is more dangerous because it's unexpected.
And because it's localized and not covering everything, it is more dangerous because it's unexpected.
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.
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#166
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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.
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.
#167
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and damnit hypno toad, quit getting sucked into this idiotic and pointless thread... I'm such a moron.
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Name just one source of liquid water in the over night hours when ambient temps are below 0f, besides car exhaust, that would cause ice to form at intersections?? Without another source of liquid water, you have nothing to create ice on the road surface.
and damnit hypno toad, quit getting sucked into this idiotic and pointless thread... I'm such a moron.
and damnit hypno toad, quit getting sucked into this idiotic and pointless thread... I'm such a moron.
Come to the Twin Cities and we will give you a real-life demonstration (-10f this morning) - absent that, this conversation is pointless, you don't believe the people that live in these conditions or the documentation that proves our point. You don't believe anything but yourself... cool, bye.
The conversation with you is indeed pointless because it is devolving into insults made only by you. If you don't agree with my calculations, do you own. Show me where I am wrong. Otherwise, at this point, you are doing what you accused me of...being a troll.
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Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Last edited by cyccommute; 02-27-15 at 11:16 AM.
#169
Bicycle Repair Man !!!
I am gonna go and ride my bike on the snow and ice today.... I should get the full meal deal of hard snow pack (my preferred winter riding surface), polished ice, and sections where you can't put a foot down despite it appearing to be clear, and where those studded tyres rule. I might even find some puddles where the concentration of road salt has kept things from freezing.
All this happens within a km of our house too.
Real world testing is where it's at, if I make it home without having crashed or being run over then the experiment will have been considered a success.
All this happens within a km of our house too.
Real world testing is where it's at, if I make it home without having crashed or being run over then the experiment will have been considered a success.
#170
meh
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I have named a source of liquid water. See post 161. Depending on the starting and ending temperature, the amount of water that air can carry varies widely and in a nonlinear fashion. Air at the freezing point can hold 4 g/cubic meter. Air at 0°F can hold 1g/ cubic meter. The water has to go somewhere.
You can see where I live. We are no strangers to winter weather. I've seen real-life demonstration of winter for many years. You can't show me a "real life" demonstration of car exhaust freezing on a road way at an intersection because it can not happen. Something else is happening but the car exhaust isn't causing it.
The conversation with you is indeed pointless because it is devolving into insults made only by you. If you don't agree with my calculations, do you own. Show me where I am wrong. Otherwise, at this point, you are doing what you accused me of...being a troll.
You can see where I live. We are no strangers to winter weather. I've seen real-life demonstration of winter for many years. You can't show me a "real life" demonstration of car exhaust freezing on a road way at an intersection because it can not happen. Something else is happening but the car exhaust isn't causing it.
The conversation with you is indeed pointless because it is devolving into insults made only by you. If you don't agree with my calculations, do you own. Show me where I am wrong. Otherwise, at this point, you are doing what you accused me of...being a troll.
I know Denver has winter, however, the Twin Cities are unique in the US (last winter):
... temperatures during the winter months are colder in the Twin Cities than in any other major metropolitan area in the continental United States, and are about equal to those in Anchorage, Alaska, which is around 1,000 miles closer to the North Pole.
Therefore, we have more experience with sub-zero temps that most places in the US. With temps staying below 0F for days-on-end, there is very little moisture in the air (the air is drier than a dessert). There is far less moisture in the air than what is coming from the tailpipe of hundreds of cars. It would be very odd that the tiny amount of moisture left in the air would only form ice at places where cars are stopped, idling. Wouldn't that ice would form on sidewalks and trees and other surfaces? But it does not, it only forms on roadways where cars are stopped idling. The source of the moisture that is forming ice on the road surface is the cars exhaust. There are dozens of source that state the exact same thing I'm saying. It's OK to say you don't have a calculation to explain this, we won't judge you, just stop saying we are wrong - that is insulting.
Last edited by Hypno Toad; 02-27-15 at 12:02 PM. Reason: I do my best proofreading after I click submit
#171
Senior Member
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A car burns around 0.1 gallons per hour idling. A car waiting for 2 minutes for a typical stoplight would burn 0.003 gallons or about 7g of gas. Through the magic of chemistry, I know that 9g of water is going to be produced per car. That's a minuscule amount of water.
Of course an individual car doesn't sit at intersection for an hour but you have many cars idling at busy intersections all throughout the day. Of course they don't just idle either, they accelerate as they move on, burning more gas and producing more water than they would if they were idling.
You were convinced that any water vapor immediately rises up and out of the way. I showed you a picture that shows that is simply not the case. As they say, a picture is worth a thousand words and that same picture shows plenty enough water to cause problems.
#172
Senior Member
Perhaps a very miserly car under ideal conditions burn that little gas in an hour. A typical car will burn 1/4 to half gallon of gas in an hour. Maybe even 3/4 of a gallon for something large. A school bus could burn as much as gallon. And as your chemistry magic showed burning a gallon of gas produces more than a gallon of water !
Of course an individual car doesn't sit at intersection for an hour but you have many cars idling at busy intersections all throughout the day. Of course they don't just idle either, they accelerate as they move on, burning more gas and producing more water than they would if they were idling.
You were convinced that any water vapor immediately rises up and out of the way. I showed you a picture that shows that is simply not the case. As they say, a picture is worth a thousand words and that same picture shows plenty enough water to cause problems.
Of course an individual car doesn't sit at intersection for an hour but you have many cars idling at busy intersections all throughout the day. Of course they don't just idle either, they accelerate as they move on, burning more gas and producing more water than they would if they were idling.
You were convinced that any water vapor immediately rises up and out of the way. I showed you a picture that shows that is simply not the case. As they say, a picture is worth a thousand words and that same picture shows plenty enough water to cause problems.
#173
commuter and barbarian
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Not all ice is invisible.
https://abcnews.go.com/GMA/video/ice-tsunami-video-photos-wall-ice-rises-lake-19166280
https://abcnews.go.com/GMA/video/ice-tsunami-video-photos-wall-ice-rises-lake-19166280
#174
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It was dark, and I had not noticed the fact that the ice was mid-freeze right as I set out. It doesn't normally get slathered in black ice all over as it did that night. Typically the weather we had means the paved areas plus a bit off the edge is dry or in the process of drying. The areas affected were so affected due to the topography of the area, with a creek nearby and the incline creating a "sink" that the cold air settled into. The ice was right in this sink. The park is always much colder than the surrounding areas, and if you go from swamp rd/bypass through to where I went down, you can feel the temperature drop as you get lower & further toward the creek. Long story short, this rarely happens & I've never gone down due to ice till this weekend.
Have you seen the 45nrth Xerces? If you're interested in using a skinny tire, it seems like the kind of tire you just leave on your bike all the time it's remotely winter at all as the studs don't come into contact with the road when going straight if you have the tire at high pressure -
45NRTH
Their Gravdal is like what you men by "slightly knobby tires", just with studs. Unfortunately you do end up with some studs down the middle no matter what:
45NRTH
If you're going for a fatter studded tire, the Kendra Klondike you mentioned does look interesting:
Klondike Standard
In that it's wide and knobby but no studs down the middle:
I wonder if the same thing would apply about using a high pressure keeping the side studs off the ground when going straight.
I personally haven't found much use for knobby tires in winter...when I tried them skinnies either cut through the snow, or there was to much snow for wider knobbies to be terribly useful. But that's personal experience and opinion of course.
I keep being interested in the Xerces, but here in Minnesota there's so much snow and ice they're not useful to me - I use a Schwalbe Marathon supreme than can handle the small ponds of ice we get on the paths sometimes lol. The Xerces seemed like a great tire for a "probably don't need studs but want to have something for the very rare ice I'll run across" kind of riding.
#175
Mad bike riding scientist
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Therefore, we have more experience with sub-zero temps that most places in the US. With temps staying below 0F for days-on-end, there is very little moisture in the air (the air is drier than a dessert). There is far less moisture in the air than what is coming from the tailpipe of hundreds of cars. It would be very odd that the tiny amount of moisture left in the air would only form ice at places where cars are stopped, idling.
The dryness of your air doesn't help your argument either. As I've said above, if the air isn't saturated, the air can absorb the water vapor that is put out by the cars. Yes, the cars are going to have clouds of vapor around them while sitting still but those clouds will quickly evaporate into the air. The water won't go crashing out on the ground in any appreciable amount...largely because there isn't that much water in the fog.
It's not insulting to say you are wrong if you are wrong. You are wrong. There's just not enough gas burned nor is there enough water produced to do what you guys are saying happens.
Perhaps a very miserly car under ideal conditions burn that little gas in an hour. A typical car will burn 1/4 to half gallon of gas in an hour. Maybe even 3/4 of a gallon for something large. A school bus could burn as much as gallon. And as your chemistry magic showed burning a gallon of gas produces more than a gallon of water !
Of course an individual car doesn't sit at intersection for an hour but you have many cars idling at busy intersections all throughout the day. Of course they don't just idle either, they accelerate as they move on, burning more gas and producing more water than they would if they were idling.
The "right conditions" is what is important. A moving car isn't a situation where there is low wind. The air around each one of those cars in tjspiel's picture is going to become turbulent the minute the cars start to move. That will stir the air, bringing low moisture air into the mix and move high moisture (warmer) air further up. the conditions would not be "right" for the formation of "black" ice.
__________________
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!