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Comment by hauget | Hacker News Reader

That looks amazing! But, if someone "gets funny" and paints a 25mph sign as 55, then what? Any countermeasures for this?

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Someone should try making a sign that says

    () { :; }; /usr/bin/media_play 'https://www.youtube.com/watch?v=dQw4w9WgXcQ'

http://gizmodo.com/5498412/sql-injection-license-plate-hopes...

I had a Tom Tom about 5 years ago that knew the speed limit on major roads. I'd imagine Google et. al. are collecting that data even if it's not publicly available in their mapping APIs yet.

How do you think that they can predict route times? It might not be part of the UI, but I'd wager they've had the data for a long time. The accuracy of the data, though, might be a reason that they don't present any of that data as fact.

Wait, what? Every navigation system I ever used showed the speed limit and was capable of giving a warning if you go to fast. And it is pretty accurate, usually maybe plus or minus a second of passing the sign. Road works or just recently altered speed limits will of course yield no or false displays but fourtunatly road works are obvious and they don't change speed limits every other day.

Google doesn't show it. I don't know if they are afraid of lawsuits or if they feel it to be a distraction or anything like that.

> I'd imagine Google et. al. are collecting that data [...]

They are. All phones who have Google Maps installed, and have enabled reporting (anonymous) position data (might be default on some phones) are helping Google both see if there's a traffic jam somewhere, and see what the actual driving speeds on the roads are (by sampling at a certain interval and seeing distance traveled over time).

I happily contribute to this, I think it's a great idea to crowd-source traffic data. I do hope Google makes the data publicly available though.

Waze[1] is all based on users' feedback and has been acquired by Google in 2013, so I think we'll see this more and more..

[1]http://en.wikipedia.org/wiki/Waze

Nokia maps did this. Also you could set a speed limit warning at your preferred limit, usually about 10% above for me. It was quite handy on long drives.

The sort of AI necessary to drive a car is not like conventional programming code. You already can not simply blindly trust a sign. As a human you're so used to converting bad signs into something meaningful or ignoring them, but it's just part of the base problem of driving, not some sort of special problem. The sign is merely one of a constellation of inputs already coming in, already contradictory (speed limit is 55, traffic is driving 65, road conditions should only be permitting about 35, what do you do? etc.).

Oops, I read this backwards.

The car should use the minimum speed limit from its set of stored speed limit signs, rules about local roads, and what it sees. If the car sees a speed limit sign that's "too high," it should call back to the mothership for a proper investigation (by the autodrive maker or the local police or both).

OLD POST (where I got your situation reversed):

It _should_ drop to 25 mph, because maybe someone in authority put a real 25 mph sign there. Then they should investigate who did that.

The countermeasure would be to take over the wheel.

The eventual countermeasure would be to have the speed limit sign broadcast its number over radiowaves, which is of course still something people can mess with, but requires a higher bar than a can of glue.

What would a human do if they saw a 25mph changed to say 55mph?

"That doesn't seem right", probably.

We have a 55 mph zone near our house that anyone not from the area seems unable to believe (as it's a narrow, fairly winding two-lane road) and you get stuck behind them puttering along at 35 for a few miles.

You're driving along a road. The signs all say that the limit is 55mph. You pass a sign that says "55mph ends." Now what?

[Note: The route to a friends house years ago did exactly this as you got away from developed areas.]

The UK's rules for what to do when there isn't a sign: https://www.gov.uk/speed-limits

Of course there's the unofficial and regularly observed "I think this is 60, but I can't see (or have no idea what is) a NSL sign so I'm going to do 45-50 to be safe"

It varies state by state and can depend on what kind of road you are on. Most states define a default speed limit for roads and highways.

Most states have rules such as: "35mph unless otherwise posted".

If you see a crazy curve ahead, you would slow down

I like that. Let the robots determine the appropriate speed limits in real time.

In Oregon the basic speed rule says that if you are going around a curve too fast to be able to stop for someone laying in the road, you are going too fast no matter what the signs say.

Maybe signs of the future should also have a QR code next to them for the real speed, just in case someone modifies the painted one. If they mess with the QR code too, then it should give a warning or something.

Sign the Speed Limit tangled with the GPS coordinates of the sign with a private key of the state. Place both the signature, GPS coordinates, and speed limit in the QR code.

Yeah, in the future the number visible on the sign will be just a courtesy to humans. The authoritative piece of info will be electronic.

A similar situation that impacts humans is someone getting funny and removing a stop sign. I guess the traditional countermeasure is to restore the sign.

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