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Comment by lucianbr | Hacker News Reader

Why not have at least radar? Plenty of cars have radar for adaptive cruise control and blind spot monitoring, it can't be that expensive. Two sensor kinds would still be an improvement.

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I think if you have two sensor systems with one being significantly less capable than the other, the gain from having both quickly diminishes. I believe Tesla dropped the radar because it was simply outclassed by the camera in 99% of circumstances. So the radar really just becomes a hacky failsafe for bery rare circumstances, and Musk would like to avoid such a situation, he wants a "clean" solution.

Sensor fusion could cover that though, cameras aren't good if they are obstructed by dirt, particles (fog, snow, heavy rain), don't capture enough light, and probably many other cases. Fusing camera input with a radar to cover shortcomings of the camera sounds sensible enough.

What I'm saying is that it might be the case that "capability c" (somehow measures as a positive scalar) of your fused sensor system is not the sum c = c_1 + ... + c_n of the capabilties of each sensor c_i, but more like c = (c_1^p + ... + c_n^p)^(1/p) where p is a large power. The case p = 1 is where every sensor contributes to the whole system with perfect efficiency. The case p = infinity, i.e. c = max (c_1, ..., c_n) is where really only the best sensor does all the work and the weaker sensors can not add anything useful. The case of p > 1 somewhat large represents that all sensors contribute but the real heavy work is being done by the best sensor and other sensors only have significant impact if they have roughly equal capability. So I believe that the team at Tesla has the intuition that p is too big for radar to be worth it.

If the cameras (or our eyes) are obstructed, you shouldn't drive at all.

People drive all the time in snowstorms around here in Sweden and Norway, lower speeds but outside of a major blizzard with zero-visibility people still drive and reasonably safely.

I used to drive through torrential storms in Brazil, where the highest level of the wipers was barely enough to keep water out of the windshield, never had an issue when keeping safe speeds either (even though Brazilian traffic is murderous).

Driving in a torrential rain can be terrifying. Literally can't see practically anything in any direction.

Haven't seen an equivalent snowstorm so far. Even in the worst case there's still at least 30 ft / 10 m visible range. Which is not great, but at least something.

In both cases, if at all possible, better to stay put!

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