In less than 2 hours the first trip of the driver-less vehicle shuttle ended in a wreck, thanks to a human. The shuttle stopped itself short of a delivery truck, thanks to the cars sensors. But the delivery driver did not see the shuttle behind it, and grazed the front bumper. Had the delivery vehicle had the same sensors the accident would have been avoided. That leaves the question, if we do have driver-less vehicles, they either need to all be driver-less or it probably will not work.
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