[CamperBob2]

Building more trains and other fixed-location transit systems that will be finished right around the time autonomous road vehicles start to become viable seems like a bad idea.

Public transit planners need to get a clue, seriously. The cars of 2050 are not going to be their father's Oldsmobile. This is more of an issue in urban environments than for cross-country transit, of course, but still... if trains are the answer, then we're asking the wrong question.

[Bouncingsoul1]

Relying on something you might have in the future seems like a bad idea to me. Infrasturcture needs constant improvements if you don'T do anything for years you might end up in a unresolveable mess.

[CamperBob2]

I know one thing we definitely won't have in the future, if we build this boondoggle: 68 billion dollars.

[guard-of-terra]

One train is like 500 autonomous vechicles on one road, and more comfortable. It will still win energy-wise. That you can hop on robotaxi after arriving makes it even more desirable.

[hugh4]

> It will still win energy-wise.

What are we basing that on? Let's look at some numbers:

https://en.wikipedia.org/wiki/TGV

Let's take the Eurostar trains as an example:

> The Three Capitals sets are 394 m (1,293 ft) long and have 766 seats, weighing 752 tonnes.

Most of the other trains seem similar. The mass is about one tonne per passenger. So in terms of mass of metal you need to drag around per passenger, a full train is very similar to a small car (say, the latest model Mazda Miata which weighs 1056 kg) occupied by a single passenger.

But of course trains are very rarely entirely full (and cars average more than one passenger). But the whole mass of the train needs to make the journey regardless of whether there's people onboard or not! The train I caught the other day was probably dragging around ten tons of metal for every passenger. This is what makes trains a horrendously energy-inefficient means of transport.

Aerodynamics? Self-driving cars could draft behind each other at high speed. Probably not a drag coefficient quite as low as the aerodynamically designed train, but it also has a colossally lower cross sectional area, because a train is ridiculously high and ridiculously wide (in the interests of not being ridiculously long, and also for historical reasons).

What else? Oh yes, the car doesn't have to stop 'til it reaches the destination, trains tend to have stops along the route.

For speed, I don't see any reason why, once self-driving is solved, you couldn't have cars cruising at 200mph+ in self-organised "trains" on the existing I-5. No present car is really optimised for that kind of thing, so it's difficult to say how hard it would be, you'd need different tyre compounds for a start.

As for comfort I'll take the privacy of my own little bubble over travelling in the close company of four hundred random strangers.

[guard-of-terra]

It won't be your own little bubble. You're not going to own a 200MPH autonomous car. You will lease it by hour.

And even that is very far away. Meanwhile trains just work. No high-speed connection between LA and SF is an anomaly by world standards given size, proximity and economical importance of two cities.

Also, modern high-speed trains don't have 4-person compartments (or have those at premium), they are rows of seats not unlike plane business class seats. You usually have power, sometimes wi-fi. You can get coffee and a newspaper.

[lorenzhs]

ICEs in Germany have 6-person compartments at no extra charge. You can choose where you would like to sit when making a reservation (compartment or open space (table or no?), window or aisle seat?), or hope that there will be empty compartments.

[CamperBob2]

You're not going to own a 200MPH autonomous car. You will lease it by hour.

I don't want to own it. I don't have to own it. The transit authority can own and operate it.

This will be so much better than fixed-track transit it's not even funny.

[guard-of-terra]

Why? I can understand that for short trips but not for 3+ hours.

[CamperBob2]

Let's try an experiment. Let's meet in the lobby of an office building in the middle of downtown LA, and see how long it takes each of us to get to a bar in downtown SF. Loser buys the drinks.

You fly at 500 MPH, I'll drive at 65-70 or whatever the speed limit on I-5 is these days.

I will win this bet, most likely. You will lose. A train won't help you much, if at all, because it's going to embark and disembark on its own fixed schedule, probably in some crappy/scary part of town miles away from where you need to go. (Here's another reason: eventually some terrorists are going to attack the train. The TSA will muscle its way in, and you'll have to arrive at the station an hour or two early, just like we do now when we fly.)

There's just too much hassle and overhead involved in multi-modal transit... which is why people who can afford to drive still do, even when they have alternatives.

[ctolsen]

Perhaps you'd like to get some actual numbers behind your claims?

And not stuff like "trains are very rarely entire full". Of course they're not. But cars are almost always entirely empty.

[hugh4]

Hey, I'm trying to throw some actual numbers into the discussion in response to the assertion that trains are more efficient. Perhaps those who want to make that claim can start supporting their own? Give me something to work with here.

Rolling resistance is the big issue that usually favours trains. On the other hand, could we design cars with an extra set of wheels or something?

[cardinalfang]

Two vehicles capable of 300kph: TGV: 500 seats 8800kW BMW M5 5 seats 440kW

For long distance/high speed aerodynamics is more important than weight.

[CamperBob2]

Then let's buy 68 million airplane tickets for everyone who will ride this train. The cost will be the same.

[CamperBob2]

No, you're not thinking of it the right way.

500 autonomous vehicles on the road are a train. Only without expensive, single-purpose hardwired tracks.

[TeMPOraL]

Expensive, single-purpose hardwired tracks that make it much more efficient for the whole vehicle to travel. 500 autonomous vehicles all carry engines, batteries, lights and a lot of stuff that is not needed when those car are all traveling together, but wastes energy anyway. Also, the price tag of those single-purpose tracks is amortized by all the millions of "cars" that travel on them.

[CamperBob2]

Something you're missing is that autonomous cars can bring an end to the era where everyone feels compelled to own at least one car, if not two. Most cars spend 1-2 hours per day on the road and 22-23 hours parked somewhere. With appropriate resource planning, a network of autonomous cars can probably serve as many people as our current urban highway systems do with 10% of the vehicles. And you can rest assured none of them are going to be burning gasoline.

People don't understand just how insanely different things are going to look in another couple of decades. Trains make sense if, and only if, everything stays exactly the same.

[TeMPOraL]

I am first to hope for the autonomous cars and ending car ownership, because IMO the current road situation is absolutely ridiculous (In the meantime, someone would please train drivers like they do train airline pilots? I.e. beat the stupidity out of them with enough training.). A PRT network made out of autonomous electric cars would be something absolutely wonderful... in a city.

But between the cities, you still have tons of cars going together, in a line, all the time. There is no flexibility here, almost everyone is going the same direction for most of the way. I don't see how even autonomous electric cars could beat trains on that. I think that the best way for the future is bullet trains/hyperloop connecting the large cities, and PRT within the city. I'm open to math that shows otherwise though.

[hugh4]

I'd never previously considered the question of what sort of speed a self-driving car could reach on an intercity freeway. No reason why it would need to be significantly slower than a high-speed train.

Think individual cars are inefficient? Not compared to a train, and especially not compared to a train that is anything other than 100% full.

[adrianN]

A high speed train goes 300km/h, some can do 400. You'd need a huge tank in your car to make it go that speed for any amount of time.

Cars need to go slower because they have worse air resistance than trains and the tires get hot and wear out quickly.

[CamperBob2]

Airplanes are even faster... yet it's possible to drive from LA to SF in less time than it would take to fly, even if you never break the present-day speed limits. Remember, it's not fair if you count the distance from one city limit to another. You have to consider the time it takes a given passenger to get from their home or business to their end destination.

Also, all it will take is one (un)lucky 9/11-style terrorist attack, and everything we've come to know and love about air travel and the TSA will instantly apply to the train station. This is a matter of "when," not "if."

Finally, there's also a hidden economic cost associated with fixed tracks, similar to the costs/risks borne by someone who buys a house. They're stuck there. A homeowner might like to move to a nearby city to take a better job, but oops, they're still underwater on their mortgage. Likewise, locations and other trends in urban economic development shouldn't be biased by a decision made 50 years earlier regarding where to put the train tracks.

It's better to stay agile, and trains are perhaps the least agile things humanity has ever built.

[jacquesm]

You could conceivably space cars closely enough when they're automated that the aerodynamic drag would be considerably reduced for every car except the front one.

You're still going to have to deal with rolling resistance and going up-hill you'd have to limit the speed of such a convoy to the speed the slowest car can attain.

But for most distances that a car will normally travel the difference between 150 and 300 Km/h will not translate into meaningful changes in time spent on the road and probably you're still going to beat high-speed rail in door-to-door scenarios.

[dragonwriter]

It seems a really good idea, to me. The autonomous autos are good local connectors to high speed rail or transit systems optimized for lnger-range travel, but not much better than existing autos add long-range travel options.

[Tinyyy]

Trains are still faster and more efficient than cars, autonomous or not.