Comment by Animats
13 hours ago
That's a tough problem - distinguishing wet pavement from deep water. Humans make that mistake frequently. Autonomous vehicles should probably be equipped with a water sensor. (We did that in our DARPA Grand Challenge vehicle back in 2005). Then they can enter water very cautiously and see if it's too deep. This may make them too cautious about shallow puddles on roads, though.
It’s a particularly hard problem in Texas. We get torrential rains and the landscape is relatively flat. Couple that with shallow soil over lots of limestone and it means flooding is really common. We also have roads that have a “low water crossing,” where a road crosses a creekbed that is normally dry but which will flood. There are often water depth signs there (basically a vertical ruler with feet marks so you can see where the water is up to). We lose people to this scenario (driving into flood waters) every year. It’s particularly problematic when it’s dark and you miss a warning sign. Before you know it, you’re in deep water and the flow can sweep the whole car downstream until it gets pinned against a tree, possibly with water forcing its way into the car.
Yeah, people are bad at guessing and the usual "Plan continuation bias" kicks in.
I was travelling in a group to eat lunch with friends once, after heavy rains. We reached a site where the road needs to fit under a bridge and is known to flood, there's standing water, and the driver figured it's probably not too high, he drives in and nope, water over the air intake, bye bye engine and we walked the rest of the way to lunch
I absolutely should have said "No, don't" but the plan says we have to drive under that bridge, there is no plan B. Of course plan A being "Wreck car" is a stupid plan, but the bias meant I didn't say "No" and I should have.
You wouldn't die there, just trash the car, the flooding is localised - but there are definitely other sites around here where in flood conditions you could die if you drove into water that's deeper than you realised.
I love the irony of how you wrote this comment. You say bye bye engine, and then the very next action is to walk to lunch. No mention of what happened to the car, or whether the driver had to stay and deal with it. Nope, the most significant effect on you was that you had to continue on without the car in the picture. Hunger is the real plan continuation bias.
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Uncle Rodney has left the crankcase.
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This case makes me think of my brother's place in rural Tennessee. To get to his house, you drive through a small creek, year round. For a hundred years in their community, they've managed without a bridge. I'm not sure driverless cars are ready for edge cases like this. Also, no one tell Enterprise I drove their rental through a creek.
Heck, that was the way I took into the city for work for a few years, shaved a good 30 mins off the commute.
You'd have to hold off for a few weeks every season change while the ice hardened up/melted or get stuck in it (thankfully I tended to get there after someone else found out).
There are many fords in the U.K., and one particularly notorious one, Rufford Ford, ate about one car a day until it shut a few years ago, and one or two people would need emergency services to rescue them every month.
Frankly, you never know when you’re going to have a bad day - I managed to inflict several thousand euro of repairs on my pickup a few months back driving through water that didn’t even come up to the axles - because unbeknownst to me some shithead mouse had chewed through the top of the fuel hose, and water got into the diesel.
So, I expect driverless cars to struggle just as much as humans do.
https://www.bbc.co.uk/news/uk-england-nottinghamshire-676414...
Texas has it easy.
I've seen several places in England (and at least one in the western United States) where they have fords.
For those not familiar, water runs over the road full-time, and people are expected to just drive through it like it's no big deal. Except for right after a storm, when it is a big deal. It's essentially the intersection of a road and a stream where a bridge should be, but nobody ever built one.
For example: https://maps.app.goo.gl/eqjHKqDxGxFNz47D7 complete with the google streetview car (presumably) driving through it
And a collection of videos https://www.youtube.com/@jawalton2001/videos - it goes without saying, these aren't major thoroughfares.
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It seems to me you could do something interesting with floating warning devices that only appear when the water's too deep.
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My dad went through one of those in England where it was a bit deep. The car had to have a new engine.
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I've lived here over a decade. Lived through multiple floods. Never once have I driven into water without being unaware of it.
Because of the replies, I can't tell if this post is dripping with sarcasm or not.
If they have a laser measurement of the road from before, couldn't they see that the level of water vs the expected road surface?
Such detailed database of fine grained road geometry gets stale very quickly, due to road maintenance and road construction. In US highway lanes are shifted sideways frequently.
But are they not continuously updating the road database with their fleet?
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I traveled to Austin 3 weeks ago and there were entire highways not on Google Maps.
Apparently they were built in just a few months.
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Pretty sure they already rely on such a database for positioning, so they already have that problem.
But yes, this wouldn't work for other self-driving systems that don't rely on HD maps.
That seems a very risky assumption for any car (self driving or human driver) during flash floods. "Turn around don't drown":
You think you know how deep it is under because you've taken that road many times before (or in your case you have historical laser measurement)
But you don't know:
- Maybe the road under fully collapsed
- Maybe the flow of water is extremely strong, so you need to accurately estimate that too.
I more meant that it could maybe see a significant difference in the road, and know to take caution, not to try to gauge the depth of a submerged roadway.
Flow should be able to be done with vision, radar can as well: some bridges use surface flow monitoring radar.
You underestimate how frequently details like this change in the real world and how difficult it is to reliably integrate them into the mapping models with very low error rates.
Aggregating this data in something close to real-time, verifying and corroborating that the change to the road model is real and correct, and then pushing those model updates to every vehicle that may need it almost immediately is not really a solved problem.
That's so much extra complexity
If they have a pre-existing database of every road, sure. And if it's kept up-to-date at all times in all vehicles.
Waymo does have a database of every today they drive, but for this they don't need one.
If the car comes to a road covered with water, and that road is in the database, and the water level appears low compared to the historical level of the road in the DB, then the car could cross. if the road is not in the DB, then a different decision might be made.
This is similar to humans: you might make different decisions depending on whether you know the road well or not.
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Isn’t that the Waymo data model, though? They extensively pre-drive every new market, building dense volumetric maps of the entire service area before they begin service, so they essentially do have that database of every road (that they drive on).
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I thought the same thing. A very small float switch would work here. Somewhere between the radiator and the bumper. Fording depth is different for every vehicle.
Going to move up and down with every bump and pothole
Have a rod that pivots in its center and has objects of equal mass at each end, like a balanced seesaw. But make one of the objects very low density (less than water) and other high density.
Since the densities differ, water will cause the rod to rotate. But since the masses are the same, bumps will create no net torque around the pivot point and thus no rotation.
ASCII art diagram:
Also include a small spring to keep the float in the down position.
I'm sure there are other ways like sensing the electrical resistance of the water.
Or just let the float sensor bounce. It's underwater when it stops bouncing and is continuously in the up position.
This is also why they recommend not to use polarized while cycling, it can obscure slicks or water in certain sections. I still use mine but I know it's not as ideal as photo chromatic lenses.
This is how I got my shoes wet climbing around rock pools last weekend.
Reminds me of all the Waymo vehicles stalled during that San Francisco blackout a while ago.
I have always believed that when people cite statistics on Waymos beating human drivers on safety statistics, that is only in the case of the happy path, or "happy road". The safety statistics could plummet in specific scenarios that lack training data or forethought, and they could crop up at any time.
There must be a term for this fallacy.
“I’d rather survive 100% of the time in situations that happen 0.01% of the time than survive 99.9999@ of the time in situations that arise 99.99% of the time”
Right, but humans are terrible at the happy path. I’d take 20% safer on the happy path over 40% less safe in unforeseen circumstances. The failure mode being “stopped car” is also not that bad.
You’re presenting a false dichotomy. There’s the third part which is “foreseen but challenging circumstances.” Also, “stopped car” can be VERY bad in many circumstances. Stopped on lane 2 of a motorway, stopped in running water, stopped in snow.
Also I suspect many “unforeseen” circumstances happen regularly. The unforeseen part is “what” and “when.”
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Pretty sure the right answer mainly involves the car knowing about the weather and other emergency events.
It doesn't take much of a rainstorm to see localized flooding. Some debris over the storm drain is enough to flood a street. Hard to anticipate that happening.
Dangerous localized flooding has also occurred for other reasons unrelated to weather, like broken dams or embankments.
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All that it can take is a broken fire hydrant in the wrong place.
Doesn't Land Rover historically have like a wading sensor?
They could be context aware and check if other cars go through and things of that nature.
By a water sensor do you mean a sensor to detect the water level relative to the chassis? It seems like a very inexpensive downward-facing ultrasound sensor could work.
When you're going 35 mph and suddenly hit a 2 ft deep puddle (I've done this), that sensor isn't going to help at all.
Going 35mph into water of uncertain depth is a bad strategy. Even well equipped jeeps approach potentially-deep water at like 5mph.
Is ultrasound less expensive than a moisture sensor?
The problem with both is they effectively require the vehicle to be in the water already. They need something that can tell depth before the vehicle has to slow down.
What kind of moisture sensor are you thinking of?
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I've used an ultrasonic sensor to detect the water level in a tank before, I don't think it would work as you describe.
Also, the sensor didn't work in that context either as condensation kept forming on it.
If they've mapped the surface of the water relative to themselves... couldn't they slowly wade in and just calculate the depth based on that 3d model without extra sensors.
Assumes there's no abrupt cliff to fall off... but short of the ability to make a 3d map underwater that seems inevitable.
They should really just park themselves on the side of the road (or observe in real time), wait for another car to go first, then follow that path
It would have to know the height of that car above ground, how high the air intake is, etc. A lifter offroader could make it through a much deeper body of water than eg. a prius.
> Humans make that mistake frequently.
They have been known to make that mistake. To use the word "frequently" demonstrates a misunderstanding between number of incidents and total miles driven. It also ignores that humans often drink and most of these types of accidents happen after 2am and most often in the state of Florida.
> equipped with a water sensor
Car washes will be fun.
> DARPA Grand Challenge
The problems the grand challenge ignores are more important than the ones it solved.
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Human drivers look for Waymos up ahead, water up to their windows.
<jk>
Do they make this mistake frequently? How frequently? I've seen people overestimate things, but I don't think this is as hard as one might think
My commaai can do this. I'm pretty sure tesla can as well
> frequently
I've never made that mistake; I'm not aware of anyone I know doing it. I very rarely see it myself, except on news footage. Of course it happens some time somewhere but that says nothing about frequency.
> That's a tough problem
Not really. Don't drive where you don't know it's safe. Definitely don't drive into moving water - puddles only, and only if not too deep: I can usually figure it out based on the rest of the road - unless it's a sinkhole, the geometry is somewhat consistent - and especially by looking at objects in the water such as other cars driving through it. Sorry your friend isn't competent to figure it out.
People here are always quick to defend the autonomous cars, like a close friend. How often will we fall in love with a technology or company? It always distorts the truth.
It’s definitely a thing humans do a lot in certain places. Perhaps where you live, it isn’t as much of an issue, so naturally you and nobody you know has encountered it.
> humans do a lot
I suppose we can redefine 'a lot' to mean many things, but 99.9..% don't do it.
It's the exhausted talking point of the autonomous vehicle industry that humans are awful drivers and we are better. What is sad is seeing HN users doggedly repeat it like PR reps - it was the first line of the original comment, even though irrelevant to it - as they've done with other passions like Uber, Musk's entities, etc.
Any human can distinguish wet pavement from a flooded street. Some voluntarily drive into the flooded street.
And that is the difference. In a Waymo you are a prisoner, in your own car you can turn around.
I rode my motorcycle into a hole that almost swallowed the front tyre entirely in rural Australia. That hole had just been a slight depression that collected water the last time I rode through it, and there was no visual indication that it was now deeper.
Any human can't necessarily tell the difference between an inch of water, which is perfectly safe to drive on (if slow enough that you don't hydroplane), and a flooded street. They can tell the difference between an inch of water and wet pavement, though.
This is the naive "if you can't stop you're following too close" circular definition based take. Makes for good rightthink points on reddit and communities of similar quality membership but you're not actually gonna build anything useful thinking like that.
In order to drive reasonably humans need to drive through water that is 6-12in deep on occasion. That's just how it is. Near me it's whenever the storm drain at the bottom of the hill clogs.
Why do you ignore the context (humans cannot distinguish?). If what you say is true, Waymos are useless in your areas. Thank you for confirming this!
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