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Comment by ansible | Hacker News Reader

I get that the vision system might have been fooled by how the lane widens before the split.

What I don't get is why the radar doesn't pick up the barrier itself. It should have been getting a nice, healthy return signal from it, lots of metal at all kinds of angles. What I'm saying is, this is not a stealthy barrier.

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The thing is, there are a lot of stationary objects alongside/near major highways (signs, bridge supports, barriers, etc.). The radar systems are not 100% accurate about whether a particular stationary object is in the lane. In nearly all cases, stationary objects are not in your lane (if they were, the previous driver in the lane would have hit them). Thus the radars are tuned to detect non-stationary objects, as those are slowing cars, merging cars, etc. all of which are commonly in one's lane, and which require action from the Autopilot.

> What I don't get is why the radar doesn't pick up the barrier itself

All of these radar systems seem to have problems with stationary objects https://www.wired.com/story/tesla-autopilot-why-crash-radar/

Radar is not active if the speed is higher than a specific threshold; it seems it is written in the manual.

> Radar is not active if the speed is higher than a specific threshold; it looks like it is written on the manual.

I'm having trouble understanding why that would be the case. Why anyone wouldn't want the radar active when going down the highway.

It is not as if it doesn't work at highway speed...

That's because he is wrong. The radar is active at all speeds. In my experience, the radar basically only identifies cars and car shaped objects.

Radar on the Teslas, if it works like how I am familiar with, just detects "things". Things that have a decent radar return. This class of things does indeed include cars and other vehicles, but should also include walls and such.

It is likely that they're using at least 2-D radar, so the system should be able to discriminate between an object directly in the path of travel, and one that is off to the side.

Sorry for not having quoted the exact paragraph in my very first comment. You can find the reference just above; it stops to work at around 90 mph (150 km/h) - Tesla Model S manual, Collision Avoidance Assist, page 95.

Additional limitations are listed in page 96.

Exactly.

"Automatic Emergency Braking operates only when driving between approximately 7 mph (10 km/h) and 90 mph (150 km/h)." -- Model S Manual (you can find it online)

if road marks have priority over radars then tesla has a huge security hole on their hand. people can just paint brighter lines at a diagonal and crash them.

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