On Aug 15, a Cruise Robotaxi mishandled a construction zone and drove into some wet concrete where the road was being rebuilt, to its great embarrassment. In a subtle dig, Waymo tweeted a video of their own car driving the same road earlier that day and handling the construction zone fine. Let’s look at how both cars did, and why Cruise should never have made that error, but also why Waymo’s drive is just what should be expected.
(In an update of a story earlier this week, it has been learned that the incident where Cruise cars stalled on the east side of San Francisco which was attributed to a communications failure caused by cell phone overload at a music festival on the west side of town was in fact due to a pedestrian deliberately blocking the vehicles and had nothing to do with the cell overload. The cell overload did slow Cruise’s handling of heavy traffic near the music festival itself.)
(Photo actually by Paul Harvey)
Waymo doesn’t mention Cruise by name but they could not resist showing off how they did driving that same street earlier that day.
To be fair, it’s not an identical comparison. The Waymo drove the street while big equipment was digging it up, it could not possibly have driven into the spot where teh Cruise got stuck. The Cruise arrived when the gear was gone and the hole they dug up was being filled with cement. That doesn’t, of course, excuse the Cruise’s mistake. It’s a bad one. Of course, nobody was hurt, and Cruise reported they contacted the city and presumably offered to make right for any delays and costs, so this is yet another of the teething pains that are well justified in the race to bring this technology to market. It’s worth examining just how robocars deal with construction like this, and why Cruise does score badly in this event.
This is a big construction zone. Typically these do not happen by surprise, and the robocar companies attempt to get updates from the city on all planned construction. Waymo says they do this, Cruise probably does too but did not comment. As such, a construction zone should not be a surprise. Even if one is a surprise it’s only a surprise to the very first car in the fleet to encounter it. Cruise has over 300 cars out on the streets and people remark they see them frequently on most streets. It seems likely that both Waymo and Cruise cars should have seen this zone before, and it should have been entered on their maps. Indeed, if possible, details about the zone — like what lane is closed — should have gone on those maps, ideally. Even so, the companies try to be able to drive the construction zone without this map info and without remote assistance.
From the Waymo video, this zone was well coned off and signed. In addition, regular traffic was following those signs well to show that the left lane is the traffic lane. Waymo drove the street in heavy traffic, the photos of the Cruise indicate a much lighter traffic period. The Waymo had to actually merge with quite heavy traffic and did it well — even better would be if its map had revealed the need for the left lane well in advance, and it had placed itself there before the merge would become difficult.
Detecting the construction
Both Waymo and Cruise use high definition maps, as do most robocar companies. (Tesla famously says they don’t use these.) With such maps, they have an image (in scanned laser light, usually) of the road service before. As they drive the road they compare what they see to that image. That lets them know where they are on the road and also tells them immediately if the road has changed, with new lane markings or road repairs. If the road surface has been entirely removed, that is usually very obvious. So it seems unlikely the Cruise car would have missed this construction zone being there. In addition, all the signs and cones should also have made it clear.
While it’s very common to encounter construction, it’s quite rare, in a large fleet for a car to be the very first car in the fleet to encounter brand-new construction that wasn’t announced by the city. In the future this should be almost unheard of. As such, it can make sense for that rare first car to ask for remote help from a human at decoding the lanes and reading any unusual signs, though the teams all hope to have their systems able to understand all common signs and cone layouts on their own.
Cruise touts that they are running many more vehicles than Waymo in San Francisco (and says that this accounts for any higher frequency of problem reports they may have.) As such it seems very likely another Cruise car would have driven this street earlier and correctly handled the construction zone, but Cruise declined to comment on this.
Unless it did that very badly, it must have simply made an error in deciding which lane to use to drive through the zone. That required major misreading of signs and cones, and also not noticing the wet cement. That’s the most understandable of the mistakes — even humans miss this and drive into it from time to time. It should have tried this out in simulation often, but whatever was tried didn’t work. The lower depth of the roadbed on the right side should have also been a clue. Detecting the texture of wet cement is not something LIDAR or radar will do easily, it’s a job for computer vision, but that didn’t do the job this time. Even so, it should not have had to. The Cruise had no business being on that side of the street.
For the Waymo, things seem to have gone as planned. It probably knew about the zone either from city reports or other vehicles driving it. It picked the correct lane, merged into it and drove the zone, dodging badly placed cones and incursions of the construction into its lane. This was an easy one, so Waymo can’t be all that proud.
We don’t have a full video of the scene at the time the Cruise drove it, and they have not offered one. Possibly the cones were removed? In the Waymo video you can see that the later part of this zone has fewer cones, and cars parked inside the cones. You could see some confusion in that sort of situation.
The short conclusion — Cruise continues to have some work to do to catch up to Waymo. Another video released at the same time should a different Cruise also driving into a construction zone, but immediately stopping in a safe place — but showing their detection here needs some work.
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