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Comment by dmitrygr | Hacker News Reader

Because those databases are out of date approximately 100% of the time...

Road construction, for example is a reason why

However if the sat nav gives you a prior that says 35 mph, and the road sign says 85 mph, do you trust it? Especially if the adjacent roads are also low speed, and it's clearly not a highway etc. This is perhaps a bad example as there are plenty of roads in the UK that transition from national to 30 in rural areas (and plenty of hamlets that you can bomb through).

Roadworks are an obvious situation where you drive at a _lower_ speed. This would be a case where you could use computer vision to identity an obstruction, identify roadworks and then adjust speed.

Those databases shouldn't be out of date. Most highway agencies (UK for sure) publish planned works and improvements weeks in advance. Google and Apple both show road closures for example. I belive speed changes are similar.

Google maps keep saying 101N in San carlos is 65mph. It's been 55mph due to construction for 5 months...

This is literally Google's back yard

65 in a 55 is much less dangerous than 85 in a 35. It wouldn’t be common that road conditions would permit very high speeds while at the same time having an artificially lowered speed limit (e.g construction).

This shouldn’t be a problem, in general, with a couple extra sanity checks.

I would expect the correct solution to more commonly have the opposite problem: too slow in a faster zone.

Even so, what's the worst-case scenario in biasing towards lower speed and assisting your vision system with a knowledge base?

You perform the task of vision 100% of the time driving. From a purely probabilistic standpoint, even assuming highly accurate ML, the relatively infrequent database updates still make for a sensible prior.

This is somewhat adjacent to what Gary Marcus has been arguing, and I think it makes a lot of sense; there seems to be no compelling reason to rely exclusively on primitives (i.e. vision) when good priors are easily accessible.

Out of date is probably not that big a deal. If a speed limit is lowered from 40 to 35, or even 65 to 55, and the database doesn't get updated, it's unlikely to create a dangerous situation if a car doesn't know about it.

But a car thinking a 35mph zone is an 85mph zone... that could be a very big deal indeed.

Regardless, if self-driving cars (or at least "computer assisted driving" cars) were to be widely deployed enough and shown to depend on these sorts of databases, I'd expect it to become a legal requirement to make sure these databases are kept up to date by city/county/state agencies, and that car systems get those updates. Otherwise, expensive liability ensues.

It gets complicated fast. Currently if there is some sort of emergency or requirement to notify road users of a change to driving conditions, a person can just put a sign up. It mostly just works. If road workers are also required to update a database that needs to be read by a car, that’s a lot of infrastructure that needs to be working. You also need to have the humans and machines reading the signs as the same at every time point, as “road closed” or “one way” needs to be correctly understood by everyone at the same time. In an emergency that may involve bad weather or some other sort of disaster, a remote database is not going to work very well. The car needs to read the actual sign properly.

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