The Situation: A self-driving car is traveling at it's maximum speed, 25 mph (40 km/h), in the middle of an empty street with the ability to change lanes on both sides. There are two passengers, one in the front and another in the back.

Someone jumps from the side of the road directly into the path of the car. A collision would occur in 50 meters. Breaking distance at this speed is about 24m.

The Question: Is it known how the current implementation of the Google Car AI would react, or is it currently a matter of speculation? A step-by-step explanation of the AI's decisioning process would be preferred.

Possible Answers: The car could activate its brakes immediately, coming to a halt as quickly as possible. This would be sooner than a human could stop, as people require time to recognize the possibility of a collision, and then physically slam on the brake. (thinking distance).

Alternatively, the car could continue traveling forward, processing the situation. (Similar to a humans thinking distance). The person may continue to move, either out of the way, or still into danger of being hit. In this case, the car may decide to change lanes in an attempt to pass around the person.

Lastly and most unlikely, the car will not alter its course and proceed to drive forward.

Do not attempt to do it to check;)

  • $\begingroup$ Related although not specific to Google's implementation. $\endgroup$ Commented Aug 4, 2016 at 18:52
  • $\begingroup$ I think you kinda answered yourself with your possible answers haha. I guess you're just looking for which one's right? $\endgroup$
    – Avik Mohan
    Commented Sep 1, 2016 at 5:46
  • $\begingroup$ @AvikMohan The possible answers section was a clarification of the author's possible explanations for how the car would stop, not in any way a "real" answer, just ideas. At least that's how I interpreted it :) $\endgroup$
    – Josh B.
    Commented Sep 1, 2016 at 14:39
  • $\begingroup$ I see, that makes sense; to clarify the answer type he wanted. $\endgroup$
    – Avik Mohan
    Commented Sep 1, 2016 at 15:11
  • $\begingroup$ At 40 km/h, my 18 year old car stops at much less than 24 meters. More like 15 meters. My car -has- to be able to stop at less than 25 meters at 50 km/h, by law but is able to stop much faster (at great discomfort to me). Not that this matters in the end (just change the distance, and you get the same problem). $\endgroup$
    – Clearer
    Commented Feb 14, 2017 at 0:45

1 Answer 1


Given this YouTube video which is being given by Sebastian Thrun who had a TED talk which had nowhere near the same level of detail but had similar conclusions, it looks like the lidar system used by google's automated car system has decent resolution out to at least 30m picking out mobile bodies in the static background and then identifying it. So it should have plenty of time to brake and stop long before there was any risk to the pedestrian attempting to cross the street.

Skip to about 6:40 in the video to see a visual representation of the detection system.


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