[nkoren]

No, not like that. Trains work well for arterial routes that need to carry large volumes of people along predictable corridors at predictable times of day -- eg., for commuting. And yes America certainly needs to get better at investing in them.

But trains don't work at all well for serving smaller volumes of people moving in stochastic patterns at arbitrary times of day. Neither do buses. Cars serve this need very well -- they also generate massive negative externalities in the process, but they do serve this need.

Why should we care about "people moving in stochastic patterns at arbitrary times of day"? Transport planners call this "incidental travel," implying that it isn't really significant. But this is because transport planners don't have a good means of addressing it. In fact, incidental travel actually the majority of trips that people take: going shopping, visiting friends, going to the doctor's, eating out, etc. The balance is about 60/40 for incidental travel / commuting.

People own cars to serve this need, because nothing else will (unless you're in a mega-city that can afford to run high-frequency mass transport 24/7). Then, since car ownership is a sunk cost, people use their cars for commuting as well, where they're really sub-optimal.

Travel demand is an incredibly heterogeneous problem, which can only be addressed with a hierarchy of modes. That includes mass transport at fixed schedules, individual transport that is on-demand, and intermediate collective transport modes that currently doesn't really exist. Autonomous vehicles with 4-8 person capacities and demand-responsive routing would solve a broad class of transport problems that conventional public transport cannot -- and could do so without many of the negative externalities of private cars.

I've written much more on the subject, if you're interested: http://archive.podcar.org/blogs/nathan-koren/article/news/th...

[aninhumer]

I think self-driving cars can be combined with public transport to serve a lot of these more arbitrary patterns effectively.

In the future I imagine, every train or bus station would have a small fleet of self-driving cars that people travelling nearby could use on-demand. I think this arrangement has a lot of advantages over using cars point-to-point.

The cars themselves can have a lower maximum speed, and lower range because they don't need to go very far, and lightweight, because they're consequently unlikely to get into high speed crashes. This also means your access road network can take up less space, and be more pedestrianised.

Additionally, because people use these cars for last mile transport, the effective catchment area of a station is much higher allowing them to be more viable even at lower densities, and also allowing less frequent stops to cover an area effectively.

Also, once people are used to using transport-as-a-service interfaces, it's much easier to make them aware of new transport options, and convince them to switch. If someone is opening an app anyway to order a ride to the shops, you can offer them a slightly cheaper journey involving a bus interchange. This in turn allows the networks to be more flexible, as you don't need to worry as much about providing a consistent service pattern for people to learn. So if you notice a lot of people go to the shops on Saturday afternoon, you can add a few buses at that time and people will start using it immediately.

[nkoren]

Yes, absolutely, you've got the right idea! I agree with you so much that I can't even find anything to quibble with, which is... unusual. Is this a subject that you're professionally engaged with?

[aninhumer]

Haha, thanks.

And nope, I have no professional experience with this, I just like trains a bit too much and want more of them. :D

[nkoren]

Well that's cool. :-) Often, people who like trains too much fail to envision them in a holistic context which includes things that aren't trains. Vice versa for people who like cars too much, of course. Or bicycles, etc. Something about vehicles just seems to breed monomania.

Even more than that, people who like transport often fail to consider it in a holistic context which includes land-use patterns, development typologies, etc. Appreciating the inter-relatedness of these things is not common, even amongst professionals. Maybe especially amongst professionals.

Anyhow, if you happen to be a coder and would like some professional experience with this, give me a shout. I run www.podaris.com, and we're trying to make it easier to build cities the way you like 'em.

[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...

[CPLX]

> But trains don't work at all well for serving smaller volumes of people moving in stochastic patterns at arbitrary times of day. Neither do buses.

Have you ever been to Switzerland?

[majewsky]

Or to Europe, for that matter.

> incidental travel [is] actually the majority of trips that people take: going shopping, visiting friends, going to the doctor's, eating out, etc. [...] People own cars to serve this need, because nothing else will

I use public transit (or just plain walking) for all of these tasks. Admittedly, this only works because I live in a city rather than a village in the countryside: When I visit my brother who lives in a small village, I arrange that he picks me up with his car from the nearest train station.

But it's nothing like grandparent's very American perspective of "public transit is only good for commuting".

[nkoren]

> Or to Europe, for that matter.

Er, yeah. I reside in the UK, and have lived and worked extensively in Europe. As a public transport planner. So I kinda know what I'm talking about here.

I use public transport for all of those tasks too -- because I live in zone 2 of London. If I lived in a much smaller city, or even in zone 5, it would be much more difficult for me to do so. The ability of public transport to serve incidental travel depends greatly on the size and shape of the city, and on your place within it. So yes, it can work for some people -- but certainly not for all people, nor even for most people. Not even in Switzerland.

America is egregious for how badly its cities are laid out; with the exception of New York, they are almost wholly ill-served by public transport. Fun fact: with an average 9% occupancy, buses in America produce more emissions per passenger-mile than single-occupancy SUVs. This is not a problem that cannot be solved with more mass transport: it requires entirely new forms of transport, or spatial reorganisation of the city, or (most likely) both.

[CPLX]

> certainly not for all people, nor even for most people. Not even in Switzerland.

I mentioned Switzerland specifically for a reason, which is that it has an unusually high number of small fairly remote towns where cars are actually banned and nearly everyone reaches them by train on relatively low capacity lines, and even the tiniest rural villages are served by well synchronized bus services, directly contradicting your statement.

There really aren't any areas of the country where car ownership is absolutely essential, or even all that desirable. Sure lots of people have cars, but almost nobody has to.

Yes, of course as you point out it's a multifaceted problem that requires land use decisions instead of just blindly building train lines to nowhere. But you present our current car dependence as inevitability. It absolutely is not, it's a public policy choice we make.

[LeonidasXIV]

> People own cars to serve this need, because nothing else will (unless you're in a mega-city that can afford to run high-frequency mass transport 24/7).

Uhm, I guess then 600.000 inhabitant Copenhagen must be this mega-city where high-frequency mass transport runs 24/7 (a driverless metro) and people use bikes to get around in stochastic patterns at arbitrary times of day (because there are bike lanes everywhere).

[alanfranzoni]

Copenhagen is exceptionally well designed IMHO, from both the biking side and the public transport side. Not all the cities are that way, and some just don't have enough room for such amenities - consider many cities in Italy with much narrower roads and many slopes, as an example.