Black ice is what you find in Pepsi/Coke slurpies/slushies up here! :lol:
Don't need a scraper = black ice. Equivalent to frost on you windshield. Nothing a bit of salt can't fix.
Layers upon layers of "ice" = ice. Translucent not transparent, if its still transparent its still quite mild.
I live in the middle of rolling hills, you don't have to remind me of what ice is. :)
If we didn't have regular passes by the salt truck/snow plow we'd have a sh*t load of ice.
I ride the bike like I drive big trucks.......if there's spray it's time to play. When the wheel spray stops, so do I.
Black ice to me is when moisture from the air condenses and freezes on the road surface. What makes it 'black' is that it conforms to the countours of the pavement so it has no sheen. Regular ice doesn't do that, and has a sheen making it visible.
My one cycling black ice experience occurred when air temperatures were a few degrees above freezing, fooling me into thinking all was well. Ground temperatures were below freezing. Boom I was on the ground so fast there was no reaction at all.
An intersection near my house growing up was prone to black ice for some reason. It must have been a depression where moist air settled. Cars would slide right through the stop sign into a churchyard. Eventually the put up a gaurdrail, which protected the lawn but caused more property damage.
The term black ice is inaccurately used to describe any type of ice that forms on roadways, even when standing water on roads turns to ice as the temperature falls below freezing. The American Meteorological Society Glossary of Meteorology includes the definition of black ice as "a thin sheet of ice, relatively dark in appearance, [that] may form when light rain or drizzle falls on a road surface that is at a temperature below 0 °C."
Above from wikipedia and is accurate.
Here in Minnesota it forms because of frost usually early in the season before there has been any salt on the roads. Once there is *any* salt residue which happens pretty early in the winter/fall season. After that, it doesn't form unless the temp gets below -8F where salt generally quits working. Our main problem is when it is deep below zero and then during rush hour the discharge of moisture from tail pipes (liquid and vapor) causes a glaze to form that is hard to see.
Black ice requires those freezing temperatures I spoke of.
Here in the metro NY area, winter temps swing back and forth through the freezing mark daily. That means that snow melts and the runoff sheets across the road (on hills) during the day, then refreezes in the evening. Since I come home in the dark, so-called black ice is even easier to miss (though I try to remember the places prone to it). Even with studded tires, it's easy to be surprised, but even if ready it does me little good if I can handle it but the car behind me can't.
So my rule is simple, no bike commute if there's ice on the roads. I save my ice riding for frozen lakes and golf courses.
BTW- another ice warning northern cyclists should be aware of. "Bridge freezes before pavement". When temps are only slightly below freezing, pavement may still be warm enough to thaw sleet or freezing rain. But overpasses cool fairly quickly to air temps and will ice up while the road doesn't. A nasty surprise for those not ready.
The term black ice here often comes into play in conditions where exhaust will freeze on contact with the pavement. It's thin, invisible, and found at intersections where cars have been idling while waiting for lights to change. This is of course a problem when cars are trying to stop at said intersection.
Winter has all sorts of ways to make the roads slippery coupled with commute times occurring while it's dark. So yes, black ice is a danger, but so is freezing rain, or a thin layer of snow on top of old snow that has been compressed to ice. However, the biggest problem areas are intersections where cars are trying to turn or stop. As a cyclist you will know when road conditions are bad and you need to be extra vigilant, but it's not like cars are going to be randomly flying at you from all directions.
Overall, I'm much more bothered by cookie dough snow than I am ice but I will concede that cookie dough snow on top of ice is about the worst.
Around here the term black ice in the news has become a sensationalized term. Every morning now in the winters with temps well established below freezing is coined black ice on the morning news.
I learned of the term black ice 12 years ago when I rode a motorcycle. It was described as spots on the road where ice would be hidden from the sun such as shaded by trees that is nearly invisible to you. Describing ice that forms from a cold ground on an otherwise above freezing temperature day is also a good description. "Black" doesn't derive from what color it is, but is derived from the fact that it is unexpected because the air temperature is not of freezing temperature.
My wife rolled her car this past January from sliding on ice and landing in a ditch on the side of the road when it was 40° out. The air temps rose quickly in the mid morning from about 28° and it started to rain. The ground temperature wasn't warmed up yet and the road was a sheet of ice. As she had left the house and the air temp was 40° and not knowing how quickly the temps had come up, ice on the road was totally unexpected.
Black ice is what people looking for an excuse call ice. Ice is ice. People forget that any time the temp is below freezing, there can be ice on the road and they should drive at appropriate speeds to assume they'll hit ice at any time.
But they want to drive fast so they just go ahead, and they made up the term "black ice" as a defense, as if ice is some kind of a ninja attack that nobody could have predicted.
I've not been affected on my bike, because if it's below freezing I ride with studded tires. I have few incidents in the car either because I actually expect ice at any moment, I check my traction and when I'm taking a curve I slow down significantly. Last time I got caught by ice and lost control was when I was about 20 years old and quite inexperienced.
To answer the OP's question, I do have problems with Black Ice too and that's why I put on studded tires when it starts to freeze and they stay on until spring. Those tires are good for the general unexpected patches here and there that occur on frozen roadways when there is enough moisture in the air to condense on the road and freeze. They help to keep you in control but you still have to be vigilant and slow down when you suspect patches of it. If there is a lot of it everywhere and cars are sliding all over then I do not ride the bike in those conditions. It's the same thing as when there is a torrential rain storm or a blizzard, stay off the bike it's too dangerous to get hit and run over or even killed.
I don't think people will be happy until someone is going in front of them dying all the water fluorescent orange so that they can be alerted that there might be ice when it's cold.
I think it is a good point to make that, with studded bicycle tyres we can ride in conditions when cars behave more like curling rocks and that like all other road users, we are put at greater risk when we are riding.
I've never had a problem with this hot-weather ice. ;)
Now actual black ice... it seems to me like I might get some here, but not yet.
Around here they don't dye it orange but they go out and spray salt on it so that people can drive any speed they like...or think they can drive any speed they like. Many times, they just end up upside down in a ditch;)
I was 20 miles away at work and trying to get to her. It took me 30 minutes to drive less than 5 miles. By the end of that 30 minutes, the road surfaces warmed back up and the ice was gone. I think there was over 40 accidents reported during about half an hour of rain.
My wife and her mother was lucky. She was on a back road going fairly slow. Just crested a small hill that had some turns after it and she said she just lost all control. Slid into a ditch and basically just flopped over on the roof and slid on the roof. Said it happened so fast. They were actually finding a spot to turn around and go back. They were only half a mile from her mother's house.
Worst part for us was, I was getting ready to pay the last car payment that Friday. The following report didn't fair so well. 2 children, 3 and 1 years old...
- "Skrak said thermometers on PennDOT vehicles recorded air temperatures of about 39 degrees and road surface temperatures averaging 37 degrees. When the rain began, the road surface temperatures dropped into the 20s, he said."
Air temperature didn't drop. The rain dropped the road surface temperature like a rock.
But the blanket statement that cars are curling rocks everywhere simply isn't true. Where I ride, for example, winter tyres for cars are mandatory, and a lot of car drivers use specifically studded winter tyres, for the exact same reasons.
Looking at the report you linked to, the overnight temperature was in the teens and it appears to be winter so the ground was cold to begin with. The very surface layer of the road may have been at 40F but it would have been a thin layer of sun warmed pavement on top of a cold subsurface. You can't freeze ice on a surface above the freezing point of water at atmospheric pressures. Just isn't going to happen. The freezing rain...and that what this was...sucked what little heat in the pavement out and froze to the ground quickly. It would have also dropped the air temp rapidly because water has a higher heat capacity than air does. You'd have to provide a mechanism by which water near the freezing point could fall though a column of air, hit the ground and freeze without decreasing the temperature of the air column. That violates a couple of important thermodynamic laws which have never been violated before. Ever.