RTK [0] systems definitely can have centimetre-level accuracy, though they require a fixed base station within 10-15 miles or so to broadcast corrections. It would also require roads to be mapped to a high level of accuracy.

I have seen self-driving test cars in Silicon Valley (frequently, especially in the last year or so) using these types of systems, so they are at least being tested. I've also heard discussion of putting RTK base stations on cell-phone towers to provide wide area coverage, but I'm not sure if much effort has been put into that. I do know vast areas of the agricultural midwest are covered in RTK networks -- its used heavily for auto-steering control in agriculture.

[0] https://en.wikipedia.org/wiki/Real_Time_Kinematic

I've heard on and off for many years (15 years?) about ad-hoc wireless networks for cars. Whether it's car to car, or car to some devices on the ground (lane marking, stop lights) so it knows where it is at in relationship to the road and other cars - and it would know if the car ahead is going to break or slow down.

Now the cars are relying on cameras, lidar to figure things out. What has happened to putting sensors on the road to broadcast what/where the roads is. Is that out of the question now because of cost?

I can see lots of potential problems with that, for instance you'd have to rely on the sensor data of that other car and you'd have to believe that other car telling you the truth. Lots of griefer potential there.

I drive a lot with my GPS (TomTom) on and it rarely gets the lane I'm in wrong, usually that only happens in construction zones.

So even if the error can be large in practice it often works very well.

It would be very interesting to see the input data streams these self driving systems rely on in case of errors, and in the case of accidents there might even be a legal reason to obtain them (for liability purposes).

> it often works very well

Well, yeah, it's not like autopilot is driving cars into barriers every day. But I don't think "often works very well" (and then it kills you) is good enough for most people. It's certainly not good enough for me.

According to the Reddit posterL

> Previous autopilot versions didn't do this. 10.4 and 12 do this 90% of the time. I didn't post it until I got .12 and it did it a few times in case it was a bug in 10.4.

> Also, start paying attention as you drive. Centering yourself in the lane is not always a good idea. You'll run into parked cars all over, and lots of times before there is an obstacle the lane gets wider. In general, my feel is that you're better off to hug one of the markings.

It kind of does sound like that autopilot is steering vehicles into barriers everyday, or it would be if drivers weren't being extra vigilant: https://www.reddit.com/r/teslamotors/comments/8a0jfh/autopil...

Seems like we need a study to assess whether the kind of protections AP offers outweighs the extra challenges it adds to a daily drive.

That's absolutely true, however, I did not mean it to take the place of whatever they have running right now, I meant for it to be an input into a system that can detect if there is a potential problem and the driver should be alerted.

Because if I interpret the video correctly either the car was partially in the wrong lane before the near accident or it was about to steer it into a situation like that. And that means it is time to hand off to the driver because the autopilot has either already made an error or is about to make one.

Either way the autopilot should have realized the situation is beyond it's abilities, and when GPS and camera inputs conflict (which I assume was the case) that's an excellent moment for a hand-off.

Don't navigation systems 'snap' to the most probable lane you are driving in based on general direction instead of your exact GPS coordinates?

A good example of this I think is when driving in tunnels, there is no GPS info there, but the navigation shows you following the (curved) road.

Good nav systems will fuse whatever inputs they can get including GPS, INS, compass, etc. in order to figure out and ‘snap’ to what road you’re on. Snapping to an individual lane is still AFAIK beyond these systems’ sensors’ capability. You will need an additional input like a camera for this that looks for lane markings.

Yes, they do that, and they rarely get that wrong.

Also, the better ones have inertial backup & flux gate for when GPS is unavailable. Inertial backup could also help to detect the signatures of lane changes and turns.

Try driving near a place with a lot of roads that are close together, like an airport. You’ll quickly see that snapping doesn’t really work, especially if you deviate from the route the GPS is trying to take you on.

I do this all the time and it works remarkably well. Amsterdam and the roads around it are pretty dense, up to 6 lanes each way in quite a few places with all kinds of flyovers and multi-lane exits.

At what speeds? I'm in NYC, similar dense road systems. At a reasonable speed, snapping still works because it knows where you came from. In stop stop stop go traffic combined with lane weaving and ramp merging I've found it is not hard to trick the gps into thinking you're on a parallel access road or unrelated ramp for a little while.

It's possible your highways are newer or less congested than ours?

Counterpoint, my Lenovo tablet running google maps often seems to get confused about lanes. E.g. it will think I'm taking an exit ramp when I am still on the main road. Once the ramp and the road diverge enough it will recover, but not before going into it's "rerouting" mode and sometimes even starting directions to get back on the road I'm already on.

That sounds pretty bad if that's the thing you rely on to get you where you're going. Here in NL interchanges are often complex enough that without the navigator picking the right lane you'd end up taking the wrong exit.

I don't use Google maps for driving but I know plenty of people that do and having been in the car with them on occasion has made me even happier with my dedicated navigation system. The voice prompts are super confusing with a lot of irrelevant information (and usually totally mis-pronounced) and now you are supplying even more data points that the actual navigation itself isn't as good as it could be.

I suspect this is a by-product of doing a lot of stuff rather than just doing one thing and doing that well.

Here in D.C. Google maps will regularly get confused about whether you're on the main road or a ramp; whether you're on an overhead highway or the street underneath it, whether you're on a main road or the access road next to it.

My FIATChrysler Uconnect system will sometimes think I'm on the road above when driving under a bridge.

Sometimes it'll shout "The speed limit is 35 miles an hour!" when I go under a bridge carrying a 35MPH road, even though the road I'm on has a limit of 65.

Is it using some other localization technique to complement the GPS? GPS at best can give accuracy within 3 meters (if I remember right). To make it accurate, laser/radar beams are shot out to the landmarks, of which precise co-ordinates are known, and using them the pin point coordinates of Ego vehicle are determined.

The highest resolution GPS receivers have two changes:

1. Base stations at known locations broadcast corrections for factors like the effects of the ionosphere and troposphere, and inaccurate satellite ephemerides. If you have multiple base stations, you can interpolate between them (Trimble VRS Now [1] does this, for example)

2. Precise measurements by combining code phase (~300m wavelength) and carrier phase on two frequencies (~20cm wavelength), plus the beat frequency of the two frequencies (~80cm)

With these combined, and good visibility of the sky, centimetre-level accuracy is possible.

Autonomous vehicles will often combine this with inertial measurement [2] which offers a faster data rate, and works in tunnels.

Many people also expect autonomous vehicles to also track lane markings, in combination with a detailed map to say whether lane markings are accurate.

[1] http://www.trimble.com/positioning-services/vrs-now [2] http://www.oxts.com/products/rt3000/

Inertial, flux gate compass.

"GPS is not accurate enough to reliably pinpoint your location to a particular lane."

My phone has GPS accurate to within 1 foot. I use it for mining location all the time. It uses differential GPS plus Inertial sensors.