It’s not the wind, it’s radiative cooling. I’m guessing it was morning, and the sky had been clear all night? The ground radiates heat away into the sky and gets colder than the surrounding air. (Which is why the ground can freeze even if the air temperature never gets below freezing.) Bridges and overpasses get even colder than the ground because it doesn’t have the thermal mass of the ground (i.e. not in contact with the rock/soil underneath, which would slow down the cooling).
I think the only practical way to warn drivers of ice ahead is to network all cars, and when one car detects wheels slipping, it will warn others. I think this would be easy with self-driving cars.
Yes.
Some cars have outside temperature gauges. My Volvo has a little snowflake which appears when the outside temperature is 36 F. or lower. Meaning be careful, there could be ice.
Also there are somewhat inexpensive indicators which are placed on road signs and will indicate freezing temperatures. Turns blue when freezing.
Like this…
The real problem with talking about “black ice” sensors is that you, or the sensor, need to see the icy condition far enough ahead to still have time & distance do something about it.
e.g. If it will take 10 seconds under current traction conditions to get down to a crawling speed to safely negotiate the icy patch, then a sensor that can only see 5 seconds ahead of you does little good. At a mere 40 mph 5 seconds is 340 feet and 10 seconds is 680 feet. Most people see the ice at more like 40 feet and 3/4th second before they’re in it. Even an automated car’s effectively instant “reflexes” won’t fix that problem.
As folks have said, the key thing that automated or semi-automated cars *could *have is the ability to communicate so each car/driver doesn’t need to learn about road conditions ahead ab initio. Net of evil haxxors of course.
I have no idea what ice you’re talking about, but I know I’ve skidded on invisible black ice.
The definition of black ice is that it is transparent:
In short, if you can see it with your naked eye, it’s not black ice.
All ice matters!
CMC fnord!
It has been tried. Rover introduced the “Icelert” as standard equipment on the 1966 Rover 2000.
The Findlay Irvine, the company that developed it, is still in business, marketing systems to monitor and report on road and runway conditions. No mention of vehicle sensors though.
99% of people really don’t know what bad conditions are. They assume that since they have handled some ice and snow, they are ready for it.
I plowed a foot of snow from our driveway at 5am on Saturday morning. I parked the plow truck and then drove 100 miles to Denver. No problem. I do have snow tires and 4x4 for my daily driver.
As far as smart cars and VDC - I did not plow where we park our cars (it was 5am and I needed to hit the road). My Wife has a brand new 2016 Subaru Outback. It does pretty well. BUT the VDC needs to be shut off for deep snow.
My Wife just tested this. Backing into where she normally parks and pulling out again. The snow was deep and rutted. The car decided it was stuck, lowered engine power/RPM and would not move. A tiny bit of wheel slip, and any momentum is lost.
She turned off the VDC (Vehicle Dynamic Control) and got right out.
Most people think they are excellent drivers (90% “way above average”). I know I am an average driver, but I have driven hundreds of thousands of kilometres in snowy and icy conditions and am a skilled winter driver.
Ice is often hard to see. It gets covered with snow. It may be white or a much darker shade. I don’t see how a detector could use temperature since roads are cold. I don’t think the expense of a more complicated system would be worth it. If it is slippery, this is often obvious. Vehicle stability is great. The trick is to tap your brakes rather than slow down quickly, avoid doing much with the steering wheel, drive somewhat slowly but not extremely slowly since winter driving is about momentum. Don’t assume everyone else drives well, never tailgate (as always), wear your belt, avoid distractions and pull over if you can’t see the sides of the road.
In Canada, moderate and major roads have good websites which describe winter driving conditions. These are very useful, more accurate than many sensors. If your car slips or you think there could be ice, there probably is.
But again, where do you keep finding me making these assumptions? All I can remember doing is to ask if anybody is knowledgeable about the present or prospective mechanisms that might make a self-driving car more capable than a manual driver to overcome certain winter driving challenges, such as extricating from deep show. Which is something that any driver can, with experience and skill, learn to do with some success.
In the US, every state has a web site to give such information. It’s helpful to find out if a road/highway is closed. Otherwise, not so much. Sure, they will let us know if there is a chain law, or icy/snowy conditions. But if you drive these roads regularly, you will already know that.
In the winter, I assume conditions are going to be bad. You always have to be ready for it.
My apologies, I misunderstood your posts.
The answer to your question is, yes, although currently the focus is making self-driving cars (well any autonomous vehicle really) work in ideal conditions. There’s been quite a bit of research lately on adapting obstacle detection algorithms to work in adverse weather like rain and snow. This is a necessary first step towards getting self-driving cars to work in these conditions. In terms, of the actual driving skills, the difficulty is always whether expert knowledge/skill can be logically encoded in some fashion. The kind of problems you’ve mentioned don’t strike me as ones which would be too hard to solve. For example, assuming the vehicle can sense the reduction in traction it should be able to determine the best possible way of driving in terms of speed, etc.
Aside from the loss of traction, there’s the question of whether the car can navigate when the lane markings (and perhaps the road signs) are obscured by snow. And what if the snow and ice block the cameras and sensors the car uses to navigate?
Too much of the country is in the snowbelt for too much of the year for the automakers just to ignore winter conditions. So I assume they will address these conditions.
My Prius has an annunciator that indicates slippage. It usually comes on about half a second after I feel the slip for myself.
Many of us are talking past each other. Bad snow conditions to one, is a six month long everyday occurrence to others.
Exactly my experience.
VDC may be protective when driving on slippery bare or lightly covered pavement, but it confers a substantial disadvantage when going through moderate to deep snow.
Exapno, if black ice is defined to be completely undetectable, then my contention is that true black ice does not exist. There exists ice which is difficult to detect, but with practice you can still learn to recognize it.
But when can you detect it? It doesn’t help if you can only detect it 50 feet ahead of you when you are driving 60 mph and the stopping distance is 304 feet.
Hint: DON’T drive 60 mph when there are freezing temperatures!
Story: I was driving 25 mph down a country road hill hidden from the sun and it was 25 F. outside. Some idiot behind me was in a hurry and tailgating me, wanting me to hurry up…
I kept my 25 mph speed and ran into some black ice. My 4 x 4 truck with studded snow tires slid into the oncoming lane of traffic! (As did the guy behind me.) Because we were going slow, easy to redirect our vehicles back into the right lane and proceed.
Luckily it was a deserted country road and no one coming.
The guy behind me decided to slow down and stop tailgating…