[skgoa]

I don't disagree. In fact I work on software for cars, so my career depends on personal transport staying relevant. However, that doesn't adress the question of whether automated cars will increase or decrease traffic.

The original claim was that automated cars will reduce traffic by being more efficient (somehow) and people sharing them for trips. I pointed out that we have the sharing aspect of the issue largely figured out already. The point I did not make, but implied, is that automating cars, buses, trains, boats and aeroplanes will not by itself have much impact on traffic. Instead only a significant shift to more shared (instead of individual) use of these transport modes would. I feel that the image of the trafficless automated transport utopia that is so often conjured on HN, reddit etc. is a massive red herring. Because the benefits people claim stem from automation actually stem from public transport.

Whether the shift to shared transport will happen or not and if it happens how big the shift will be, are completely open questions as far as I can see. I believe that, trips for commuting have lots of scope for being bundled into shared/public transport. Meanwhile the bulk of other trips will continue to be made largely with personal transport. (And I make no claim as to whether those vehicle are owned by the end user or by a fleet operator, that's an entirely different debate.) Not coincidentally, this is exactly what happens in many big european cities that have both good public transport and the road infrastructure to allow for lots of cars to travel at the same time. Many people over here commute daily by public transport, bycicle, rideshare etc., but they also have at least one car for those other trips.

[nkoren]

Okay, so we definitely agree that automation-driven traffic-less utopia is a red herring! Certainly if personal vehicles are replaced 1:1 by automated personal vehicles, congestion will, on average, get worse. Even if they're replaced by automated taxis -- eliminating the need for parking -- this will lead to at least a ~30% increase in vehicles actively on the road due to empty vehicle movements. And that's before you factor in induced demand, which would be significant.

Where I think we disagree is here:

> we have the sharing aspect of the issue largely figured out already.

No, we really haven't. With non-automated vehicles, sharing only works in situations where you can amortise the cost of a driver. This requires maintaining an average occupancy of > 25 people, which in turn limits you to fixed routes at fixed schedules. Hence, bad for serving incidental demand. Automated vehicles open up the possibility of having a range of smaller vehicles that are demand-responsive yet shared. This would bridge the gap between current private and public transport options, serving a substantial travel regime where current technologies are inefficient.

[skgoa]

I agree, shared automated small shuttle buses that travel on ad-hoc generated/adapted routes are probably going to be a thing. BTW thanks for this thought-provocing discussion.

[nkoren]

Likewise! :-)

[majewsky]

> Because the benefits people claim stem from automation actually stem from public transport.

What about more efficient use of roads because automated cars have a shorter reaction time and thus do not need as much safety distance between them?

[nkoren]

Reaction time is a relatively small factor in safety distance. Kinetic energy is a significantly larger factor. Currently, humans violate this as a matter of course, which is why we're so bloody unsafe. Automated vehicles will be far more punctilious, which at higher speeds means that the gains from reaction time will be more than offset by the respect for kinetic energy.

What's interesting is that automated vehicles, coordinating their interactions, should be able to accommodate additional traffic much more smoothly than human-driven vehicles. They will accommodate it by slowing down. Counter-intuitively, capacity is maximised at around 10 mph (16 km/h).

Here's a spreadsheet for doing those capacity calculations: https://docs.google.com/spreadsheets/d/1F3w5-hcopm2GBGz3UswN...

For humans, the reaction time is ~1 second. If you take that down to 0.1 seconds, you'll notice that the 10 mph capacity increases by about 1/3rd. That's not too shabby! But at a more acceptable 50 mph, the capacity increase is only 15% -- and that's if humans drove safely, which they don't. Actual capacity increase versus actual human driving behaviours, at highway speeds, can be expected to be nil.

Conclusion: automation will only bring capacity gains if roads get slower -- probably much slower.

[nkoren]

Actually, here's a more digestible illustration of the capacity gains from automation: https://docs.google.com/spreadsheets/d/e/2PACX-1vQ6ga2atFS69...