Self-driving cars cannot plan an entire exchange in a dense urban areas because there will always be actors like pedestrians, cyclists, and stray plastic bags that do not participate in planning and act adversarially to their shared model. Optimizations will be highly local, spatially and temporally, and I suspect they will end up looking a lot like humans trying to coordinate on the same problem. And even if AVs can technically plan and execute faster, their actions will need to be artificially slowed to be legible to humans. Likewise with their raw speed — cars, self-driving or not, are already moving too fast in urban areas. Reaction times might improve but braking distances will not.

So if AVs can't increase the throughput of city streets, I'm skeptical that they can increase the throughput of off-ramps which are bounded by city streets, or urban freeway segments which are bounded by the off-ramps. And even imagining that significant (2x?) throughput is achieved, it's not going to meet the induced demand ceiling; there would be the same amount of congestion, only with more cars.

L5 is dead on arrival as congestion-mitigation technology and I hope at least some of the billions earmarked to be spent on researching and deploying it are redirected towards better walking, cycling, and transit amenities instead.

Self-driving car networks have the benefit of not being bound by the same finite capacity of a network of humans trying to manage real-world traffic.

Neither would they have to operate at artificially handicapped speeds, as no human operator would really be able to keep up regardless with the 10,000 or 100,000 cars running around.

Part of reacting and mitigating acute issues is being able to reroute traffic early enough, or slow cars down early enough, to minimize disruption (instead of a traffic slinky blocking everyone up).

There's no reason so far here that self-driving vehicles can't improve traffic and overall throughput, and it's a bold claim to declare L5 dead on arrival.

In a dense urban area, the speed limit is generally not dictated by road design but by the simple physics interaction between a person made of meat and bones, and a multi-ton metal vehicle.

Follow distances in urban areas with low speeds are already really small. I don't think AVs would make them meaningfully tighter.

> Part of reacting and mitigating acute issues is being able to reroute traffic early enough, or slow cars down early enough, to minimize disruption (instead of a traffic slinky blocking everyone up).

This was supposed to be what Waze and Google Maps were set to achieve, and they did not, but they did piss off a lot of people when cut-through drivers started jamming up their formerly quiet residential neighborhoods.

It's hard for me to guess how much something like this would reduce delays caused by traffic compared to the increased number of cars driving due to the fact that some driverless cars would be out with no passengers heading to pick people up.

> By offering laminar rather than turbulent flow.

That's only going to work on roads that are AI-only.

There are already cities where buying a car is difficult and/or expensive because of traffic concerns. Singapore, Beijing, Shanghai, Tokyo, ...

I don’t see an AI requirement to be a huge hurdle for those cities.

There are other actors on the road, namely pedestrians and cyclists. Unless we're going to remove the right of citizens to the street at all, they will be present and will need to be accommodated for.

Computers can or will deal with the other actors as well as humans do now, which is quite a low bar anyways.

My point is that unless you get rid of them completely, traffic flow is not going to increase. You can't have free-flowing traffic everywhere and also have pedestrians safely crossing the street, and the lower bound on a traffic light cycle today is the amount of time it takes an old person to cross the street from curb to curb.

That neglects limited access roads and wide boulevards. In either case, even if pedestrians aren’t banned, they are rare enough to be an exception rather than a rule. For example, the old guy trying to make their way across 8-lane Chang-an Road in Beijing...well, there is a reason Chang an road forces pedestrians onto bridges.

By and large, today the congestion problem is not really on the massive roads themselves, but where they interface with low-capacity local networks. Most destinations are not located on a limited access road by definition, and the busy exit into city center with lots of pedestrians is not going to get any less congested, AVs or not.

In modern Western urban planning, large car-capacity streets aren't considered a good thing to be running through urban areas anyways. Most of the large cities (Paris, Berlin, New York) are taking steps to reduce road widths to more equally distribute the road between pedestrians, cyclists and transit users. As it turns out, building pedestrian overpasses at a convenient enough spacing for pedestrians is extremely expensive.