Radar cruise control in the fog

Discussion in 'Prime Main Forum (2017-Current)' started by MikeDee, Jan 23, 2020.

  1. MikeDee

    MikeDee Senior Member

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    I've been impressed as to how well radar cruise control works on the highway. It gets foggy where I live in the winter. Can using radar cruise control in the fog help prevent an accident (i.e., rear ending the car in front of you)?
     
  2. mistermojorizin

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    It's saved me in the fog a few times, where i didn't even see the car and the DRCC registered a car in front and started slowing down. The downside of radar is it's not perfect at detecting stopped vehicles (or else your car would slow down for all sorts of stationary things on the side of the road, or so I've read).

    I experiment when there's no fog, and I wanna say it picks up stationary cars in front about 60% when I'm at speed. The alternative would be a visual system though, and I already have my eyes peeled for stopped cars and would probably react faster than DRCC which tends to have a bit of lag built in.
     
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  3. Trollbait

    Trollbait It's a D&D thing

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    I wouldn't put faith in it. The manual for my Camry has a section covering situations in which the DRCC can miss the car in front of you. Fog is listed as a weather condition that can hinder the sensor from detecting other cars. Water on the emblem/sensor can be enough to interfere.

    https://www.toyota.com/content/ebrochure/CFA_TSS_Precautions.pdf
     
  4. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    I seem to recall Owner's Manuals saying to not use cruise in bad weather, especially at night. Maybe that goes out the window with radar cruise? Not sure.
     
  5. mistermojorizin

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    They're just covering their a$$, what else you think the lawyers will have them say? The advantage of radar is being able to penetrate fog, otherwise they'd be using a vision system like subaru. Disadvantage is detecting stopped cars.

    I mean, it's a drivers aid. It's safer to drive with it on in fog than with it off in my personal experience.
     
  6. fuzzy1

    fuzzy1 Senior Member

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    I certainly hope that no one here is depending on radar cruise to avoid hitting others in fog. It is still just a backup or assist, not a primary means of collision avoidance.

    Even in fog, primary avoidance must still be by ordinary visual contact. If you can't see it in time, then you are going too damn fast, and committing a prima facie violation of the Basic Speed Law. This is how so many massive pileups happen on foggy highways.
     
  7. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Water vapor is quite good at absorbing and attenuating radio frequency signals.

    I love automation, but I would not be able to trust a radar cruise in heavy weather at night.
     
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  8. fuzzy1

    fuzzy1 Senior Member

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    And nobody (in the general public, at least) should be trusting it now. Doing so is irresponsible, suicidal, and possibly homicidal as well, until self-driving systems are certified for general consumer sale. That simply hasn't happened yet.
     
  9. Trollbait

    Trollbait It's a D&D thing

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    Says the same for DRCC

    Driver's aids aren't intended to allow the driver to exceed the safe driving limits of the driver for the road, traffic, and weather conditions. It has a narrower field of view than the driver, and can misinterpret incoming signals. It can't see around bends. May not see empty flatbeds and trailers, nor vehicles with a high ground clearance. Then the sensor is right behind the grill emblem. An unknown hit in a parking lot could knock it out of alignment.

    I think @bwilson4web reported his Prime's DRCC not properly detecting in mist.
     
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  10. mistermojorizin

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    Am I claiming it's perfect? No. It doesn't always detect stopped cars.
    Is it safer than driving without DRCC in heavy fog? Definitely.
    I'll share my experience as well as some more empirical data (bottom of this post) to make my argument.

    I drive to work through heavy fog (1hr drive) for 4 months a year. I'd rather make that drive with DRCC than without it. My last car had full-speed radar adaptive cruise too. Just sharing my real-life experience.

    Keep your foot hovering over the brake pedal so you can brake faster than if you had your foot on the gas to maintain speed (this is how I was taught to use cruise control anyway way back when I went through driver's training). Set the speed to something comfortable (but not too slow, or the cars without DRCC might hit you from the back).

    DRCC has helped me a couple of times in heavy (*heavy*) fog, detecting cars I couldn't see.

    Even if everything you say is correct, I'd rather make the drive with DRCC rather than without it for 2 reasons:
    1) I can keep my foot over the brake to speed up braking.
    2) It detects most cars before you can see them so you have more time to slow down.

    Here's a video of using radar cruise in fog (different car, but as long as it's radar, it'll see through fog, at least better than a human):


    And here's basically a professional writer explaining what I've been trying to explain in this post:
    TECH: We test three adaptive cruise control systems... - CAR magazine

    Here's a scholarly article from 2017, which reads in relevant part
    https://www.mdpi.com/1424-8220/17/2/271/pdf

    So again the choice is drive with DRCC or drive without it? I also suspect that I'm more comfortable in the fog because I'm used to it. Most people in my area are very comfortable with it. We have to drive and I'm telling you, it's safer with DRCC than without it, and science tends to confirm this.
     
  11. mistermojorizin

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    Airplanes actually do use radar (radio frequencies as you mention) and they fly through the thickest of fogs and lots of water vapor, as you can imagine.

    How radar works | Uses of radar - Explain that Stuff
     
  12. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Sure, but I think you can appreciate that there are some differences between the packaged appliance radar included in a commuter car and the combined efforts of ground-based meteorological and flight tracking radar and the airborne radar systems on transport aircraft and the people maintaining and supporting those systems.

    I regularly trust our air transportation system so I can travel for work. I'm not ready to place the same level of trust in a fancy cruise control gadget yet.

    With regards to the example you posted, I've got personal experience with highway travel within South Africa. The writer you've cited is using a radar system as a hack to stay safe in an environment where ordinary traffic control measures as well as common sense have failed. Road traffic should slow or halt for fog or other limited visibility conditions.

    If you find yourself 'covering the brake' with your foot at the ready, you've probably already made a dangerous mistake in terms of speed choice or following distance.
     
    #12 Leadfoot J. McCoalroller, Jan 25, 2020
    Last edited: Jan 25, 2020
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  13. fuzzy1

    fuzzy1 Senior Member

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    I will never argue that drivers in fog should turn off DRCC. Only that DRCC must not be used as an excuse to drive faster than one would without having DRCC.
    80 km/h (50 mph) in impenetrable fog??? :eek::eek::eek:

    That is a deathwish. That is how we create multi-vehicle pileups of 40 or even 100 vehicles. People die. But at least the heat from any fires will speed up the clearing of the fog.

    Fully autonomous vehicles will cure this. But such vehicles are not yet ready for the consumer market. Too many people's expectations are getting far ahead of technical reality.
     
  14. fuzzy1

    fuzzy1 Senior Member

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    Penetration and attenuation are quite frequency (or wavelength) dependent.
     
  15. Tideland Prius

    Tideland Prius Moderator of the North
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    The Prius uses millimetre-wave radar. I suspect noise is heavily masked.

    Still, you’d think it’ll be attentuated by water vapor droplets from the fog.
     
  16. jerrymildred

    jerrymildred Senior Member

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    And not just fog. Rain. Snow. Ice. A few years ago, we drove all the way across Iowa on I-80 in the ice. It took FOREVER! But we made better time than the ones who drove faster. The ditches looked like a giant kid had dumped out his toy box for 300 miles. Thankfully, almost all the other drivers had had their wrecks by that time and there were no closures so we had the road almost to ourselves.

    The pile-ups keep piling up and the news reports do nothing to help by saying the wrecks were caused by the weather. Then again, if they correctly reported that the wrecks were cause by people not properly adjusting their speed and following distance to accommodate the weather, most drivers would be too dumb and impatient to catch on. Don't forget, half the population has a less than average IQ. ;)
     
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  17. john1701a

    john1701a Prius Guru

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    The answer is no.

    The reason why is simple. Radar is always active, since it is an essential aspect of the auto-braking system.

    So, regardless of whether you have cruise engaged, it will be actively working to prevent an accident anyway.
     
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  18. m8547

    m8547 Active Member

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    Adaptive cruise control brakes a lot sooner and more gently than auto emergency braking. If the road is even a little slippery, auto braking won't do much for you.

    I've tested DRCC in whiteout snow conditions. It doesn't work. It just drives as if there's no car in front of me, and it doesn't give any indication that it's ability to see is impaired. A moderate amount of snow in the air or a light amount of slush/snow/ice on the sensor are enough to make it stop working.

    If the sensor gets covered with an excessive amount of ice sometimes the car will give a warning message, but it stops working long before that.

    I don't understand why the radar sensor and the forward camera are not heated. The area of the windshield in front of the forward camera is often frosty for a while after my windshield is clear.
     
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  19. john1701a

    john1701a Prius Guru

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    The question was about preventing an accident, not being safer. You are safer not using the cruise on slippery roads.
     
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  20. fuzzy1

    fuzzy1 Senior Member

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    Spokane had a mass crash event last month (I think), though it was multiple piles in a short distance, not a single pile.

    News indicated that officers gave most drivers citations for driving too fast for the conditions. One young driver quizzed his ticketing officer to declare a numeric speed that was legal, and was upset that the officer refused to give a number. He seemed not to understand that the officer cannot possibly give such a number because there is no single number that is good for all similar situations. It varies, depending on driver skill, tires, and ever-changing road and weather conditions.

    The real answer is that one must drive slow enough, and with enough following distance, to avoid striking vehicles ahead or departing the road. The mere fact that he ran into someone ahead was prima facie evidence of violating this regulation. It is on him, not the officer, to figure out a safe legal speed.
     
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