4 ms·

I assume this is because the metal bars in the cattle-grid appear as a very reflective object in the cars' radar sensors which it interprets as an obstacle? I

I assume this is because the metal bars in the cattle-grid appear as a very reflective object in the cars' radar sensors which it interprets as an obstacle? I can see this would be a problem with cars that use only radar or radar+ultrasonic. Besides Tesla (and Waymo) cars which do sensor-fusion with vision, what other cars attempt to corroborate radar data with confirmation it's an obstacle and not a coincidental highly radar-reflective object?

Arnt 6y ago
No, it's because the grid was angled relative to the road (and the surrounding hillside). If you regard the road as level, that grid was a sudden steep incline or decline, and after that the road suddenly returned to level. They fixed it by reworking the road so get rid of the suddenness.
- DoingIsLearning 6y ago
  So the profile of the barrier was interpreted by the RADAR module as a small metal wall in front of the car?
  - Arnt 6y ago
    From the radar's point of view going uphill, the road disappeared. The radar would see a horizon, and empty air in front of the car, like the edge of a cliff. From its point going downhill it would look like an angled metal wall, or a bump, or something, and then the horizon and empty air beyond it.
DoingIsLearning 6y ago
I was under the impression that some of the Tesla crashes into highway barriers were exactly because it relied too much on the stereo vision and not enough sensor fusion with RADAR or long range Ultra-sound?
- avianlyric 6y ago
  Highway barriers are different problem. RADAR, and I think ultra sound, has very poor angular resolution. So it’s very hard to distinguish between and object directly in front of you, from one just off do the side. As a result cars ignore RADAR data about stationary objects when the car is moving at speed. The assumption being those stationary objects are things like highway barriers to side of the car. You don’t want the break slamming on just because your driving parallel to the highway barrier. Consequence is that cars ignore stationary objects like highway barriers, when moving at speed. So if you’re heading straight at it, the car won’t slow down. But then the assumption is that the human really ought to notice they’re driving at a wall.
HPsquared 6y ago
Probably the bars are square and thus act like corner reflectors (retroreflectors), giving a very bright radar return similar in intensity and position to the right angle at the base of a wall.

Arnt 6y ago

No, it's because the grid was angled relative to the road (and the surrounding hillside). If you regard the road as level, that grid was a sudden steep incline or decline, and after that the road suddenly returned to level. They fixed it by reworking the road so get rid of the suddenness.

DoingIsLearning 6y ago
So the profile of the barrier was interpreted by the RADAR module as a small metal wall in front of the car?
- Arnt 6y ago
  From the radar's point of view going uphill, the road disappeared. The radar would see a horizon, and empty air in front of the car, like the edge of a cliff. From its point going downhill it would look like an angled metal wall, or a bump, or something, and then the horizon and empty air beyond it.

DoingIsLearning 6y ago

I was under the impression that some of the Tesla crashes into highway barriers were exactly because it relied too much on the stereo vision and not enough sensor fusion with RADAR or long range Ultra-sound?

avianlyric 6y ago
Highway barriers are different problem. RADAR, and I think ultra sound, has very poor angular resolution. So it’s very hard to distinguish between and object directly in front of you, from one just off do the side. As a result cars ignore RADAR data about stationary objects when the car is moving at speed. The assumption being those stationary objects are things like highway barriers to side of the car. You don’t want the break slamming on just because your driving parallel to the highway barrier. Consequence is that cars ignore stationary objects like highway barriers, when moving at speed. So if you’re heading straight at it, the car won’t slow down. But then the assumption is that the human really ought to notice they’re driving at a wall.

HPsquared 6y ago

Probably the bars are square and thus act like corner reflectors (retroreflectors), giving a very bright radar return similar in intensity and position to the right angle at the base of a wall.