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Old July 9th, 2004, 02:23 PM   #21
SkyTaxi
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Sky Taxi is a multimodal personal automated transport (PRT + Dual Mode + other modes). It is a best solution of transport problems of cities in the near and far future. Sky Taxi will substitute cars, public transport and light trucks in city centres and suburbs.

You can download the presentation of Sky Taxi concept from the Internet:
http://members.optusnet.com.au/~spro...ko/skytaxi.pps
PowerPoint 2003 viewer for the presentation can be downloaded from the Microsoft’s website: http://www.microsoft.com/downloads/d...displaylang=en

PRT is a small automated people mover, which go to any destination on light elevated guideway. Dual Mode combines ability to go on elevated automated guideway and on conventional roads. Different projects of PRT and Dual Mode exist in the USA (were subsidized by the Federal Government), Canada, European Union (subsidized now by EU), South Africa, Norway, Russia, South Korea (subsidized now) and many other countries.

But Sky Taxi is the only viable concept. It contains some non-patented inventions and service features, which are result of the analysis of mistakes and omissions in other projects. The advantages of Sky Taxi are: beautiful cheap guideway, high speed and throughput, safety and comfort, weatherproofness, noiselessness, low electricity consumption, variety of convenient transportation modes (including several cargo modes) and variety of vehicles, adaptability to any type of city/suburb (both Hong Kong and Los Angeles!) and to any part of population. Sky Taxi is based on existing technologies only, and therefore there are no technical risks.
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Old July 9th, 2004, 04:42 PM   #22
Ned Luddington
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Quote:
Originally Posted by SkyTaxi
PRT is a small automated people mover, which go to any destination on light elevated guideway. Dual Mode combines ability to go on elevated automated guideway and on conventional roads. Different projects of PRT and Dual Mode exist in the USA (were subsidized by the Federal Government), Canada, European Union (subsidized now by EU), South Africa, Norway, Russia, South Korea (subsidized now) and many other countries.
Please name these projects and the amount of subsidy.
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Old July 10th, 2004, 12:19 AM   #23
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This proposal was planned for Cardiff in Wales. They built a test track an vehicles and seemed all for it but I think the project was recently scrapped.

http://www.atsltd.co.uk/
http://www.cities21.org/ultra/
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Old July 10th, 2004, 01:19 AM   #24
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I don't like how you can't escape exactly when you want to and how the system would still be very crowded and expensive. The real solution are little flying helicopters for one person. Hopefully over time the price will go down.
http://www.time.com/time/2001/inventions/go/infly.html

Obviously it's a futuristic project that we may have to wait a while for.
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Old July 10th, 2004, 04:04 AM   #25
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Self-navagatable transport.
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Old July 10th, 2004, 04:06 AM   #26
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Monorail like things.
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Old July 10th, 2004, 10:02 AM   #27
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Vehicle size not related to capacity

Quote:
Originally Posted by Shado
I'm not seeing how PRT could carry significant numbers of people without major major infrastructure. This Group Rapid Transit seems much more capable though. Basically just higher frequency LRT that adapts to where people want to go and how often.

Otherwise it looks like it would end up much like a taxi rank, with a long wait for a vehicle.
A key to the PRT concept is that a small vehicle is light weight, therefore its guideway can be small. This small guideway is less expensive per mile because its design is simple (no moving parts), its fabrication requires fewer materials, and it requires less intensive engineering to place in the ground. Depending on the company, cost is anywhere from $1-2 million to $12-15 million per mile. Compare to light rail's $50-200 million per mile, and monorail's $100-$180 million per mile. Thus, it is affordable to build more miles of PRT.

Small vehicles are practical for mass transit. Look at cars-- the vast majority are only carrying 1-2 people, yet cars carry about 95% of passenger miles in the USA. By being on-demand, 1 PRT car can pick someone up from a station, carry them nonstop at 35-40 mph to any other station in the network, then pick up another fare. One vehicle therefore can carry a number of different fares per hour. Imagine one vehicle can make 6 trips per hour-- what could 5000 vehicles do per hour? Per day? It's multiplication, folks.

The other key is that on-demand service means that riders waste little or no time waiting in stations. Big crowds do not develop, so PRT stations can be small. The standard Skyweb Express station ( http://skywebexpress.com ) is about 30 feet long and costs less than $300,000. So you can put a lot of them in a lot of places.

I recently re-estimated a PRT system for Seattle, which is about 79 square miles. Each square mile would have 4-5 stations linked by 2 miles of guideway. The result is 158 miles of guideway and over 300 stations. At $10 million per mile, this system would cost $1.58 billion-- less than the cost of the planned 14 mile, 20-22 station monorail, and with immensely better geographic coverage and quality of service.

Last edited by Mr_Grant; July 10th, 2004 at 10:20 AM.
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Old July 10th, 2004, 10:10 AM   #28
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PRT and the disabled

Quote:
Originally Posted by Shado
To be basically a car replacement you would need it to at least accomodate disabled people and those with some sort of luggage.
PRT designers realize this. The Skyweb system's vehicle and station designs are ADA compliant. If you visit their site, http://skywebexpress.com, there are photos of two people in the vehicle, one in a wheelchair. It can carry 650 lbs including baggage. Each station will have a hydraulic elevator.

The ULTra vehicle also accommodates wheelchairs. Its stations will have ramps or lifts (it's British).

I quote the group SoundPRT:

"PRT is the first transit system that treats everyone equally: no matter who you are or where you live, a city-wide PRT system provides non-stop transit, 24-7. How can it do this? Because there are 4-5 small stations per square mile, everyone is within walking distance of a station, and service is on-demand. Neighborhoods no longer have to compete for routes or service allocations, and service no longer ceases late at night."
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Old July 10th, 2004, 10:17 AM   #29
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Scrapped?

Quote:
Originally Posted by Prestonian
This proposal was planned for Cardiff in Wales. They built a test track an vehicles and seemed all for it but I think the project was recently scrapped.

http://www.atsltd.co.uk/
http://www.cities21.org/ultra/

The ULTra project states it has met the technical and cost objectives of its 2003 testing program. It was certified by the UK government to carry passengers.

The reason the program has been stalled-- not scrapped-- is purely political. Although ULTra is mass transit, it is not a bus or a train, so some people with influence who like trains and buses have fought it. See:

http://icwales.icnetwork.co.uk/0750e...l&siteid=50082

http://faculty.washington.edu/jbs/it...x%20Trials.pdf

http://icwales.icnetwork.co.uk/0100n...l&siteid=50082
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Old July 11th, 2004, 05:22 AM   #30
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"The reason the program has been stalled-- not scrapped-- is purely political. Although ULTra is mass transit, it is not a bus or a train, so some people with influence who like trains and buses have fought it."
"The reason the program has been stalled-- not scrapped-- is purely political. Although ULTra is mass transit, it is not a bus or a train, so some people with influence who like trains and buses have fought it."


The PRT proponents always have an excuse for why their silly scheme never gets off the ground.

Another thing they like to do is invade other peoples' message boards en masse. If you are wondering where all these PRT folks are coming from, look here:

http://groups.yahoo.com/group/prt-talk/
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Old July 11th, 2004, 09:05 AM   #31
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Quote:
Originally Posted by Ned Luddington
Please name these projects and the amount of subsidy.
Those projects were bad, and they have discredited the idea of PRT. You'd better see my PowerPoint presentation (see the link in my previous posting).

You can find everything about PRT and Dual Mode here: http://faculty.washington.edu/jbs/itrans/ .
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Old July 11th, 2004, 10:23 AM   #32
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What type of energy do they run on?
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Old July 13th, 2004, 07:53 PM   #33
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Quote:
Originally Posted by Ned Luddington
"The reason the program has been stalled-- not scrapped-- is purely political. Although ULTra is mass transit, it is not a bus or a train, so some people with influence who like trains and buses have fought it."


The PRT proponents always have an excuse for why their silly scheme never gets off the ground.

Another thing they like to do is invade other peoples' message boards en masse. If you are wondering where all these PRT folks are coming from, look here:

http://groups.yahoo.com/group/prt-talk/
When they are unable to find flaws in the PRT concept, the fallback tactic of opponents seems to be to attack those who support PRT.



Quote:
Originally Posted by Taipei101

What type of energy do they run on?
PRT systems run on electricity, so a system itself would not emit pollution. There are currently 3 types of propulsion planned by the different companies: 1. Skyweb: linear (magnetic) motor for propulsion and braking; 2. ULTra and MicroRail: rotary (electric motor turns wheels); 3. SkyTran: passive maglev system called Inductrak.


References: Linear motor explained,
http://www.force.co.uk/page2.html#WHAT

Inductrak,
http://www.llnl.gov/str/Post.html
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Old July 14th, 2004, 03:06 AM   #34
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In urban areas, PRT is more convienent than mass transit. But with so many low capacity vehicles running around, the system would become very congested just like cars on roadways. The energy usage would also be very high compared with mass transit.
Few people would use it in the suburbs, as cars would just be more convienent.
Are there any ridership models/traffic flow simulation data available to prove me wrong?
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Old July 15th, 2004, 11:52 PM   #35
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Re: PRT congestion

Quote:
Originally Posted by alabamaken
In urban areas, PRT is more convienent than mass transit. But with so many low capacity vehicles running around, the system would become very congested just like cars on roadways. The energy usage would also be very high compared with mass transit.
Few people would use it in the suburbs, as cars would just be more convienent.
Are there any ridership models/traffic flow simulation data available to prove me wrong?
Supporters are not prescribing PRT for all communities. For example, in a city with little congestion and a fast bus system with frequent service, PRT would be good but not superior-- nor would conventional rail.

The maximum vehicles/time on PRT guideway depends on the length of the vehicle, average speed and minimum headway (space between vehicles, in seconds). With a speed of 40mph and headway of 1 sec (58.6 ft), and a 10 ft long vehicle, the mathematical maximum # vehicles passing a point on the guideway is 76.9 per minute (4614 per hour).

Furthermore, unlike cars on a road, each PRT vehicle can be reused by many different riders one after the other, many times per hour. Thus, the 4614 per hour would also include multiple trips made by the same vehicle.

Because PRT guideway is configured in a network, vehicles take different routes between different origins and destinations-- vehicles are not confined to exactly the same tracks, as in a train corridor. 4614 vehicles per hour thus would represent a "point maximum", not a network maximum. In a previous post I mentioned a theoretical network with about 160 miles of guideway. It is obvious that it would be very difficult to max-out a system having that much mileage.

The system couldn't be maxed-out in reality, because the number of vehicles is set. Suppose you had a PRT fleet of 5000 vehicles on a 160 mile system, and the average journey was 5 miles at 40 mph. Each journey would take 7.5 minutes; add 45 sec at each end to board and unboard passengers, for a total time of 9 minutes per journey. Each vehicle therefore could make 6.7 such trips per hour. Thus, 5000 vehicles could make 33,500 trips per hour.

Is this enough? Consider that bus ridership in King County, Washington averages 13,000-14,000 per hour.

The other opportunity for congestion in a PRT system is in the stations.
The question is, can the stations handle the passenger throughput?

Here's what happens if you want to ride on PRT. You walk to a station; select a destination from an ATM-type machine, pay, get a ticket. It is possible you could already have a card pre-programmed with favorite destinations. Service is on-demand, so a car is usually waiting. You swipe your ticket or card through a reader, the door opens, you get in, sit down, press a Go button, the door closes, you depart. All of this does not take very long; once you select your destination, boarding probably take 15-20 seconds. When you get to your destination, the door opens and you get out.

At 15-20 seconds, a single station berth can handle 3 arrivals or departures per minute, or 180 per hour. Most stations would probably be 3 berths, or 540 per hour. In busy places (office buildings, malls, schools, arenas) there could be up to 12 or 15 berths per station (15 berths is 2700 arrivals or departures per hour). In a 160 mile network with 360 stations with an average of 4 berths each (1440 total berths), the mathematical maximum throughput is 4320 arrivals or departures per minute, or a theoretical 259,200 per hour. This is far more than the demands that could be placed on the system by a 1000, 5000 or even 10,000 vehicle system.

Regarding energy consumption, PRT systems would actually use less energy per passenger than conventional transit. This is because service is on demand, PRT cars move only when someone needs them. Trains and buses must make their scheduled runs with empty seats-- even when they are all empty.

Makers of the Skyweb Express PRT system (http://skywebexpress.com) have done many simulations for prospective clients. There may be some studies on their websites, and I'm sure someone there could provide more information by email. See also the http://skyloop.org organization for an example involving Cincinatti and the old baseball stadium. Skyweb and ULTra http://atsltd.co.uk also have information on their sites about energy usage.
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Old July 16th, 2004, 02:24 PM   #36
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The problem that I can see is that the cars have to load/unload single file. Unlike a taxi rank, where each vehicle can move out individually as they finish boarding, the cars behind cannot move until the cars ahead are ready to go. This would then block the arriving cars, which starts to line up behind the station, then out to the main guideway, then...
Just imagine a city where everyone travels by taxi, but all the roads are exactly one lane wide and there is no passing allowed anywhere......
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Old July 16th, 2004, 05:31 PM   #37
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there is a separate rail just for the station, the other cars bypass teh station on another rail

ie

<---(rail)------------------------------------>
\--------(station)---------/

but there is a disadvantage if only 1 car can unload at a time...
also the card system will be good, get in and out of the car faster, i also like system if some-one is pranking the car will be redirected to the police station.

i personally like this thing being built, but it may cost a fair amount with all the stations and high tech stuff...
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Old July 16th, 2004, 11:06 PM   #38
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Quote:
Originally Posted by Syd-Hk
there is a separate rail just for the station, the other cars bypass teh station on another rail

ie

<---(rail)------------------------------------>
\--------(station)---------/
I understand that the stations are built off mainline spurs. I'm saying that when cars queue up on the spur it will eventually back up onto the mainline. The cars won't actually need to physically be lined up out the spur for traffic jams to occur. 235 ft was quoted as the space needed to decelerate and accelerate in order not to interfere with the 40 mph cars on the mainline. Any time the space remaining on the spur line is less than this, the cars will need to start decelerating out on the mainline, slowing the main traffic flow.

Mr. Grant, you "demonstrated" system capacity by assuming traffic always flows smoothly at 40 mph. With so many stations and complicated flow patterns, local capacity can be exceeded at various choke points (such as stations) and jam up.

The station flow rates also seem a little optimistic. 15-20 sounds reasonable for loading/unloading, but it also takes time for the cars to decelerate in/accelerate out of a berth. It will take, at best, 10 seconds for the next car in queue to pull into position and be ready for boarding after the departure of the previous car. As station lengths increase, it would take even longer for the cars queing at the end to pull into position, further decreasing station flow rate.

One big crowd who's cars arrive at a station at close to the same time (rush hour traffic) would be all it takes to creat a traffic jam at the station and the surrounding area.

The reports I read at the websites provided did not address local flow either, but merely system averages, which doesn't adaquately reflect real flow at peak times.

The system seems to have very little margin for overflow - it still appears to me it is very easy to jam up, because of its combination of lots of little vehicles on random schedules competing for space on a restrictive and inflexible guideway(s).
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Old July 17th, 2004, 03:30 PM   #39
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sorry i didn't notice that ! but i agree with you now.
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Old July 22nd, 2004, 09:30 PM   #40
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Hi Alabamaken, Syd-Hk;

Since Mr_Grant seems to have taken a week off, perhaps I can help explain the station dynamics some. I have co-founded a PRT advocacy organization (www.acprt.org) and have spent way too much time studying the Taxi 2000 station design and simulation programs. Please pardon me if the explanation seems a bit long - I will try to as concise as possible.


You are right about the queue challenge - If the queued cars back up too far, they would block up the mainline guideway. There are two design responses to this problem that the system implements.

1. The stations are sized to meet the anticipated rush-hour flows so that vehicles can be handled as fast as needed to avoid over-filling the queuing area.

2. In the event that the queue area is full when another vehicle needs to enter the station - it is commanded to 'wave-off' - continue down the mainline and use the first available chance to loop back around to try again. Since the PRT system is laid out as a set of inter-connecting loops, the vehicle can return to the station within a few minutes.

In the Taxi 2000 design, each station has a queuing area on the spur between the deceleration area and immediately before the station berths. This allows vehicles to decelerate, then pause in the queue while the cars in the station load and unload. Since the deceleration area must be kept clear, no vehicles are allowed to enter the siding guideway when the queue area is full.

Before discussing the wave-offs more, I would like to describe the station dynamics that I have observed from the station simulators. For this example, imagine a five-berth station with a queuing area for five vehicles. We can number the berths (from downstream to upstream) as B1-B5 and the queue spots as Q1-Q5. Let's start with all the berths being empty and the queue spots all have vehicle waiting.

Alabamaken points out the it will take about 10 seconds for a vehicle to pull into the berthing spot prior to unloading. This is reasonable, but remember that the vehicles can be moving simultaneously. So in our example, the vehicle in Q1 will pull up to B1, taking about 10 seconds. But the car in Q2 doesn't wait for the first car to finish, it can start moving just after the first one does. So it moves Q2 ---> B2, taking about 10 seconds but starting a second after car 1 does. Cars 3 - 5 do the same, each takes the same 10 seconds to move (since they are going the same distance), but starting about a second after each other. So in this example, five cars will move into position, with the last one starting to unload after 15 seconds.

This last car is the one that generally determines the minimum time the process takes. Since it started loading/unloading last, it tends to be the last one left. If a car in front of it in the berths takes a little longer to load or move out of the station, it simply waits a few extra seconds before moving forward and allowing other cars to enter the berthing area.

While the 5 cars are loading, any cars coming into the station will be pausing in the queue area, waiting their turn to move into the station and unload. So what you see in the simulations is that as the station traffic approaches the design max for the station, cars enter the siding at random times, aggregate in the queuing spots, and move in batches into the station to unload. The cars tend to complete loading in roughly the same order as they entered, since that is the order they stopped. As they finish, each one moves as far forward as it can, with the first in line accelerating up the siding and merging onto the main guideway as it gets a chance. Then the cycle repeats.

So, for this example, the last car takes 15 seconds to move into position and another 10-15 seconds of loading time before moving forward. If we round the total up to 30 seconds, then we have two batches of five cars every minute - or 600 vehicles/hour.


Now, about the station sizing and wave-offs. One of the strong points of PRT (IMO) is that the stations can vary in size from a general minimum of three to a max of around twelve or fifteen berths. The main way to minimize wave-offs is to correctly estimate the requirements and make sure the station and queuing area is sized correctly. Taxi 2000 has suggested the queue contain a number berths equal to the number of station berths, plus an additional one or two spots and that they can hold the number of wave-offs to about 1 in every 10,000 trips.

You can decrease the chances of a wave-off occurring by extending the station queue area or increasing the number of berths, but there is always a chance, no matter how large the station, that some combination of arrivals and departure delays will overflow the queue - so it becomes a cost/benefit and policy decision when deciding how much to spend and where an acceptable level of wave-offs lay.

The likelihood of occurrence and the cost, in extra-trip time, to riders that suffer a wave-off can be compared to the effects of traditional transit bus or rail running late, having mechanical problems, or otherwise suffering a delay. A one-chance in ten thousand doesn't seem too bad when compared to the on-time performance of our bus-based systems.

The extra trip time is also affected by the guideway layout. In areas with a dense network, the time will be shorter than areas with fewer, larger guideway loops. The transit agency my choose to adjust the station size to minimize wave-offs from stations that would incur the greatest time delay.




Chris J. Burr, Co-Founder
Austin Citizens for Personal Rapid Transit
www.acprt.org - [email protected]

Last edited by Chris_acprt; July 22nd, 2004 at 09:33 PM. Reason: Corrected mistyped example B2 ---> Q2
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