BIKE: RE: PRT -- just for fun

[chris]

Sorry about the delay Patrick.  The Man called and I am one of those poor
unlucky souls forced to work to make a living.

While the Monorack M-1 certainly looks like a blast to ride up a 45 degree
incline, I am not sure the PRT community can claim it.  From the photos,
there doesn't appear to be any way for the vehicle to switch tracks, which
would be required to provide non-stop service in a guideway network.  

>From your earlier post:
<< 
PRT suffers from the same problem that the use of private automobiles 
does:Use of a (relatively) large container to transport a small number 
of people. 
>>
PRT would have substantial space advantages over the POV system we have
today. 

1. See http://kinetic.seattle.wa.us/nxtlevel/prt/hwy.html for an example
similar to the pavement packing photo of how a fully automated PRT systems
would supply a large throughput on small footprint.  

2. Most of the right-of-way needed for a PRT system already exists above
public roadways. See  http://www.acprt.org/Skeptic_Right_of_Way_Costs.cfm
for some points on this.

3. A PRT network would substantially reduce the need for automobile parking
within the service area.  Each PRT vehicle would serve 40 to 50 trips a day
as it is re-used by different patrons.  The PRT vehicles themselves would be
stored in much more dense storage facility than automobiles, and that
facility can be located on less desirable land. 


<< 
Consider what would happen at rush hour - would hundreds of 
people just line up waiting for their turn to get into a PRT vehicle?
>>
Hundreds of people already line up to get into their traditional mass
transit vehicles, but one core goal of PRT is to eliminate long waits.  This
is done by sizing each station to the expected passenger flows, so that the
more-or-less constant stream of passengers is met by a more-or-less constant
stream of empty vehicles that they can board in short order and be on their
way.   The flow matching won't be perfect, so there will be some waiting
during peak hours.  Still, simulations of city-scale systems suggest that a
properly configured PRT system can produce wait times of under one minute
for 90% of passengers during peak hours.  In non-peak hours, the PRT system
should have enough vehicles to keep empty vehicles waiting in the station
for passengers - resulting in a zero wait time.

<< 
In some ways this is actually even worse than the use of automobiles, as 
there is only "1 lane" and everyone is trying to get in their "cars" at 
roughly the same location.  Also, consider the logistics of stopping at 
stations.  Does every PRT vehicle stop at every station? 
>>
Hmmm, perhaps I am missing the questions on this one.  PRT systems should be
deployed as a network of inter-connecting lines.  You can see the ACPRT
counter-proposal to the 2000 light rail system at
http://www.acprt.org/PRTForAustin.cfm , and the Minneapolis  CPRT's user
maps at http://www.cprt.org/usermaps.htm for examples of potential system
layouts.  The network has a lot more stations than a line-haul system will,
so there are many small stations allowing users to board and alight, rather
than a few large stations that try to serve a large area.

Each station is placed on a siding line next to the main travel line.
Vehicle going to that station switch onto the siding, decelerate, and enter
the station.  Those that are not required at that station continue
un-impeded down the main line.  Thus, the system provides non-stop service
from any station in the network to any other station in the network.  No
intermediate stops while others get on or off of the vehicle.

Each station has a room for a line of vehicles to park nose to tail along
the siding and allow users to board or debark.  The number of spots (or
berths) can be varied from about three to twelve, allowing the station to be
sized to handle larger or smaller passenger flows.  Vehicles are loaded in
parallel - so each vehicle can load/unload at the same time as other
vehicles.  A queuing area on the siding immediately upstream allows vehicles
to stay out of the main line while waiting for the station to clear and
allow them to pull forward.  The Skyweb Express home page has a graphic of
this station design at http://www.skywebexpress.com 

A good analogy would be the single-lane drop off area at an elementary
school.  Each parent pulls forward as far as possible before discharging or
loading their kids.  When finished, they pull forward if they can or wait a
few seconds for the car in front to finish and move. When they are at the
front of the line, they can pull into the street and make room for others.
If there is room for five cars at the loading area, up to five cars may be
loading or unloading at the same time.

<<
If not, how would the switching be handled, especially with hundreds of such

vehicles on the track all at the same time?  The switching thing seems 
like it would be a big problem for this technology, at least give the 
state of the art.
>>
Switching is a bit different from the large-vehicle systems which use
moving-track switches.   Since the PRT vehicles travel very close together,
a track-based switch is too slow to allow the switch to move and lock
between vehicles.  Instead, each vehicle has a switch component (or steering
in some designs).  This way the system has the time between the previous
diverge point to the next point to throw, lock, and confirm that the switch
is in the correct position. 

I see that Nawdry has supplied some information on the Taxi 2000 switch
design.  ACPRT has a demo of this switch action at
http://www.acprt.org/switchdemo.cfm  and they have info about it at
http://www.skywebexpress.com/150e_switch.shtml .  Nawdry makes a point that
the switch hasn't been tested.    Such testing would be a requirement of any
system that is put into passenger-carrying service.  In this regard, the
Taxi 2000 switch design is very simple with few moving parts, it will be
inspected on a regular basis, carries a relatively light load,  and will
operate in very controlled environment.  Compare it to the steering system
on a car, which most people seem quite comfortable with.


<<
 And if every vehicle stops at every station, why not 
just clump groups of users together into larger vehicles for the sake of 
efficiency?  Oops, we're back to monorail.
>>
The don't - as explained above.  


Well, I hope that answers some questions.  Have a great evening.


Chris J. Burr, Co-Founder
Austin Citizens for Personal Rapid Transit
www.acprt.org - chris  

-----Original Message-----
From: Patrick Goetz [mailto:pgoetz]
Sent: Wednesday, July 21, 2004 3:14 PM
To: chris
Cc: 'forum-bicycleaustin.info'
Subject: PRT -- just for fun


chris wrote:
> Below are some comments from a PRT supporter's perspective on some of
> today's PRT related comments.   While I don't expect them to sway many of
> the dedicated mass-transit supporters, I hope the list finds them useful.
> 

You didn't respond to my issue regarding how switching would be handled, 
but no matter.

It turns out that there actually is a PRT system in use today (in Japan, 
of course), although monorail enthusiasts like to think of it as the 
world's smallest monorail:

 
http://www.nikkari.co.jp/english/product/monorack/catalog/jyoyo/e-taninzu.ht
ml

The Monorack M-1 has been around since 1966 and was introduced to aid 
farmers maintain and harvest their mandarin orange orchards. Because of 
the success of the Monorack, various configurations have been developed 
over the years for other small scale operations. The name "Monorack" was 
coined from "work becomes easy," which is "monoraku" in Japanese. The 
monorack system provides easy transportation of people and loads on 
slopes without the need to cut down down trees or clear large areas. As 
the Nikkari website states, Monoracks can be used in the construction or 
maintenance of dams or power transmission steel towers, for farming on 
inclined land, harvesting of orchards, and for carrying people or 
luggage at leisure facilities. (text harvested from the News page of 
www.monorails.org)