
The road not taken: How we found and lost the dream of Personal Rapid Transit - samsolomon
http://www.theverge.com/2016/2/24/11094524/prt-transit-history-self-driving-cars-alden-starrcar-tomorrowland-1960s
======
Animats
A criticism of PRT systems: [1]

Classic problems:

\- Capacity isn't high. One track equals about one freeway lane.

\- One broken vehicle stalls the whole track.

\- Real guideways are usually much bigger than pictures of proposed guideways.
You need emergency walkways, rescue access, and earthquake resistance. This is
also true of monorails.

\- Somebody has to clean all those vehicles.

Light guideway systems do exist. Intamin, the roller coaster manufacturer,
also makes monorails. Theirs are as narrow as roller coaster tracks.[2] Here's
their towing and rescue vehicle in action.[3] But their systems are low-
capacity and slow. Japan has many monorails with serious passenger capacity,
but the guideways are big.[4] One design has a flat guideway that would work
for a PRT.

[1]
[http://www.lightrailnow.org/facts/fa_prt001.htm](http://www.lightrailnow.org/facts/fa_prt001.htm)
[2]
[https://www.youtube.com/watch?v=7HInUerMfWU](https://www.youtube.com/watch?v=7HInUerMfWU)
[3]
[https://www.youtube.com/watch?v=70q_CoLT3Eo](https://www.youtube.com/watch?v=70q_CoLT3Eo)
[4]
[https://www.youtube.com/watch?v=lUpIl25q1nk](https://www.youtube.com/watch?v=lUpIl25q1nk)

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CalRobert
Worth noting - a lot of the benefits of PRT are realized with short, one-way
on demand car rentals. Obviously you still have to drive, but you get quick
access to a vehicle, go where you want, hop out, and someone else gets to use
it. At scale it's awesome, but it's been hard for sprawling US cities to get
to that scale given entrenched habits.

Here in San Diego I use Car2Go - [http://car2go.com/](http://car2go.com/) .
It's awesome for stuff like airport runs - I walk to the car (they're about a
5 minute walk from the airport), tap a card on the windshield, drive home
(about six bucks and fifteen minutes; cheaper than the bus if my wife is with
me), and then when I'm done with it the car is there for someone else to use.
They're small, nimble, electric, and fun. Unfortunately they don't seem to be
hugely popular since SD is very, very sprawling and their home range is fairly
small.

~~~
jessriedel
Is there a problem with cars piling up in certain locations? One-war on-demand
bike rentals often need to be "re-balanced".

~~~
CalRobert
Well, there's no "stations" per se, they're just parked on the street, so it's
not like a bike share where you can wind up unable to finish your trip. When
you're done with your trip, you just park (assuming there's a spot, but since
they're Smart Fortwo's that's usually pretty easy).

What can happen is that all the cars wind up some ways from you, but in the
last 9 or 10 months that's happened to me once or twice. Even then, it was
only a ten minute or so walk.

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pjc50
The book on 'Aramis' mentioned is
[https://en.wikipedia.org/wiki/Aramis,_or_the_Love_of_Technol...](https://en.wikipedia.org/wiki/Aramis,_or_the_Love_of_Technology)
; I picked it up by chance in the room of an anthropology student many years
ago and found it fascinating.

It's a sociologist's view of an engineering project management failure, and
therefore requires a bit of unfamiliar jargon to interpret. It concerns itself
with the question "what is progress and modernity?" quite a bit, as projects
like PRT are self-conscious attempts to build a futuristic technology rather
than an incrementalist approach of meeting immediate demands.

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awjr
A slightly different version of this called Bus Rapid Transit is really really
successful in the UK and is being rolled out to other cities (Manchester and
Bristol).
[https://en.wikipedia.org/wiki/Cambridgeshire_Guided_Busway](https://en.wikipedia.org/wiki/Cambridgeshire_Guided_Busway)

Extremely painful to put in place but once in place hugely beneficial.

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m0llusk
The road not taken yet, perhaps? The proposed SkyTran PRT variant has levels
of efficiency that are at least in theory way ahead of anything that surface
roads and wheeled vehicles can offer. Just as the PRT system highlighted in
the story is retained for its genuine value other experiments are likely to
tried and retained.

~~~
DennisP
Skytran is about to complete a pilot project in Tel Aviv, and has others in
the works:

[http://fortune.com/2015/11/24/skytran-maglev-pod-system-
tel-...](http://fortune.com/2015/11/24/skytran-maglev-pod-system-tel-aviv/)

[http://www.fastcoexist.com/3052942/the-sci-fi-skytran-
monora...](http://www.fastcoexist.com/3052942/the-sci-fi-skytran-monorail-may-
be-our-most-practical-replacement-for-cars)

~~~
Animats
No, they're talking about building a small test loop Real Soon Now. Their site
has a huge collection of renders and animations, but very little about real
hardware.[1] Supposedly they had a 220 meter prototype for an amusement park
in New Zealand, but there don't seem to be any pictures of that.

The hype to hardware ratio is strong in this one.

[1] [http://www.skytran.com/](http://www.skytran.com/)

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haxel
What about variably-autonomous cars? Take a car with self-driving capability
and then have it be manually operated while solitary but increasingly self-
driving as the group of similarly automated cars it belongs to grows. There's
a lot of benefits to group awareness: share sensors, coordinate behavior for
efficiency, instant communication, and so on.

This gives us the best of both worlds: safety in numbers, safety in automation
and sensors, and it retains the personal autonomy we're used to. All while not
requiring 100% perfect autonomous capability.

If the cars were small and cheap enough, they could be made available via
subscription (much like a lease) and treated like a municipal transportation
network that's superior to light rail and bus networks.

~~~
jsprogrammer
A herd of sufficiently smart enough self-driving cars should be able to use
their network of sensors to allow "manual" drivers to move freely through,
should it not?

I would think that one should be able to drive even more freely; as the
reaction time of the herd, and the individual cars, could accommodate
situations that even highly trained human drivers would fail at.

~~~
haxel
Yeah, I would think that such a herd or swarm would be fully backward and
forward compatible. Traditional cars could keep doing what they do - swarms
would react intelligently to them as swarms tend to do - and there wouldn't be
any need for specialized infrastructure to support pure automation.

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jkot
I think this would create problem with monopoly. If city would own and rent
out cars, the price would inflate and technology would stagnate. Something
like city licensed taxi services.

~~~
floatrock
How else could you raise the vast amounts of financing needed for such a
project? It's not unreasonable that if you put forward $100M on a risky
venture, you get x years of exclusive usage to generate a return on
investment.

The article mentioned a failed kickstarter for a boston project -- the
crowdfunding alternative has yet to be proven for large-scale infrastructure.

But it would be interesting if you could raise a bond like that from private
citizens. Literally have people invest in their city by purchasing shares of
the municipal bond and have it paid back over 30 years of usage. Not sure why
that can't be done... perhaps easier to mobilize $100M from a single private
equity group than $1k from 100,000 individuals, perhaps rules about being an
accredited investor before you're deemed ready to invest in projects of that
scale, or perhaps the lawyers are terrified of dealing with a class-action
suit involving a chunk of the populace instead of a small number of private
equity firms in the lawsuit if things go wrong.

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curtis
I wonder if it would be economically feasible to build a modern equivalent of
the Morgantown PRT using a standard electric car model (Nissan Leaf, Chevy
Bolt, etc.) as the "pods" using nothing but after-market modifications. Such
an approach might make sense if new systems like this were dominated by R&D
costs -- and, maybe as importantly, R&D schedules.

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13thLetter
Here's an idea: what if we built lots of personal rapid transit vehicles, but
made them operate on the ordinary cheap-to-build-and-maintain roads that
already exist, and sold them outright to the end users so there was no need to
maintain a massive centrally controlled network? That could be a game-changer.

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jessaustin
I can't help it; every time I read "PRT" I think "Parahuman Response Team".

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Shivetya
well self driving cars are being over engineered for the very fact that for
very long time if not forever there will always be a manually controlled
vehicle along their path.

as for lane set asides, we already have HOV and Express lanes that would
easily be adapted to self driving cars, if anything the express lanes would be
even more efficient.

Cars like buses always trump trains in metro ranges simply because both can
adapt quickly to change of habits. trains might be one solution between cities
but even in Europe air travel is supplanting it

~~~
CalRobert
"if not forever there will always be a manually controlled vehicle along their
path."

I hope it is forever, because otherwise we apparently would have outlawed
bicycles.

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xyzzy4
Instead we pursued the dream of 140 character messages.

------
josscrowcroft
I'm excited about the Hyperloop:

[https://en.wikipedia.org/wiki/Hyperloop](https://en.wikipedia.org/wiki/Hyperloop)

[http://news.nationalgeographic.com/energy/2016/02/160223-Elo...](http://news.nationalgeographic.com/energy/2016/02/160223-Elon-
Musk-Hyperloop-for-Sonic-Tubular-Travel-Gets-Real/)

[http://www.wired.com/2014/12/jumpstartfund-hyperloop-elon-
mu...](http://www.wired.com/2014/12/jumpstartfund-hyperloop-elon-musk/)

