The ultimate light rail concept

[monsoon]

If we can't believe those who analyze transit characteristics for a living, who can we believe?

That isn't a qualification for believing someone's numbers on whether this is a good technology or not. And I am very doubtful these systems can be built and operated for lower cost than traditional mass transit. The maintenance of thousands of cars in a large system is going to be very high, the energy claims are not realistic, and it simply can't handle the number of people as a LRT or HRT.

[prtsupporter]

The maintenance of thousands of cars in a large system is going to be very high, the energy claims are not realistic, and it simply can't handle the number of people as a LRT or HRT.

On what are you basing these claims?

Through testing, ULTra has been shown to use less energy than other forms of transit: ULTra PRT Environment

This page calculates system capacity of a PRT system and how the same math used for LRT can't be used for PRT.

[GRDadof3]

On what are you basing these claims?

Through testing, ULTra has been shown to use less energy than other forms of transit: ULTra PRT Environment

This page calculates system capacity of a PRT system and how the same math used for LRT can't be used for PRT.

prtsupporter -

Are you in any way affiliated with skywebexpress (or another PRT developer)? If so, you're getting dangerously close to breaking the rules about advertising your business (hocking your product) here.

[prtsupporter]

prtsupporter -

Are you in any way affiliated with skywebexpress (or another PRT developer)? If so, you're getting dangerously close to breaking the rules about advertising your business (hocking your product) here.

No, I am not affiliated with any business or company that produces, designs, or in anyway is associated with PRT.

I believe PRT has great potential to provide great public transit service in cities. I'm just frustrated by unfounded dismissive claims of the technology like "it will be a maintenance nightmare", "high energy usage", and "low capacity". Since so much research has already been done throughout the world and many of the results are available on the internet that show the feasibility of the concept, I can't just let these obviously wrong statements stand.

[Rizzo]

I am sorry, but if this was such a superior transit mode, it would have been implemented atleast somewhere... I still see LRT and BRT implemented time and time again, why not PRT? Probably because after 40 years! the concept and design dosen't work. If it did, wouldn't it have been implemented! 40 years! c'mon... Lets debate PRT in GR rather then the entire concept, or drop it for that matter, this my last post to the thread.

[foo_gr]

The problem I see is people getting to where they want to go. For instance, say I want to go to the local grocery - I should walk, could walk, but it is cold so I'll drive. A hop on and off of one of these will take too long.

Alternately, say I want to go to work - that would be cool, but I work in the 'burbs. Even if I can get close, how do I cover the "last mile."

In GR, we think of trips in terms of cars. In a denser city, where cars are impractical, the mind set is different - trips are though of in terms of how to use public transportation to reach the proximity of a destination.

I think urban sprawl has much to do with the (im)practicality of public transportation in GR, but I would really like to see something that works. Imagine if you had this type of system, and could tear up roads, and put down grass and bike/scooter paths - that'd be great.

[prtsupporter]

if this was such a superior transit mode, it would have been implemented atleast somewhere

PRT History

PRT History 2

Computer technology has come a great way in the last 10 years, now at the point where small, cheap, fast, redundant systems are realistic. Other technologies have similiarly matured. These kinds of advances make a PRT system practical today.

Additionally, any large public transportation system needs significant government support. Due to political inertia and ties to existing transit modes, as well as a lack of a proven system in operation, many government officials fail to give technologies like PRT a reasonable chance.

[monsoon]

The vast majority of cost of implementing a transit system is not in the technology of the system but in right of way acquisition. PRT has no advantages there in fact it is at a distinct disadvange compared to certain kinds of rail as it can't go onto shared tracks with freight. The fact of the matter is you cannot build a public transportion system these dayw without government funds, and the government has some very strict rules on how this money is parceled out. The PRT people have to first get their system approved by the FRA, or there simply won't be any systems built in the USA.

In regards to the other claims that I have made, anyone will tell you that a system with thousands of moving parts compared to one with dozens is more complicated, more expensive and will use more energy. Its engineering. It is incumbant on the PRT developers to prove otherwise and research studies on paper are not going to do that.

[prtsupporter]

The vast majority of cost of implementing a transit system is not in the technology of the system but in right of way acquisition. PRT has no advantages there in fact it is at a distinct disadvange compared to certain kinds of rail as it can't go onto shared tracks with freight.

Yes, it's true that PRT probably wouldn't share track with other systems. Because it won't, it won't be affected by anything that happens on those other tracks. We know what happens to auto traffic when a long freight train crosses a road: traffic backs up. Since PRT would be on it's on captive guideway, it would always be able to provide consistent service.

PRT systems are expected to usually be completely on elevated guideways that require only one support post every 60 or 90 feet of linear track. The post, in some designs, would be about 2 feet in diameter at the base. A series of posts along an existing road is much less land to acquire than nearly every other type of rail system. Look at a conceptual drawing.

anyone will tell you that a system with thousands of moving parts compared to one with dozens is more complicated, more expensive and will use more energy. Its engineering.

I don't understand your argument here.

The design for a Taxi2000/SkywebExpress vehicle has only 14 moving parts, including the door. Propulsion is provided by a linear induction motor, which has no moving parts, but uses magnetic fields. This is existing technology used in other areas already. The guideway would have no moving parts -- the switch would be in the vehicles.

Non-stop motion uses less energy than acceleration/deceleration. This is physics. A PRT vehicle would travel non-stop from it's origin to the destination. Buses and trains stop at every stop any passenger wants to get on or get off. Those vehicles are so heavy that accelerating from a stop uses a lot of energy.

Per passenger mile, ULTra has shown by measurement on their prototype vehicles that they would use less energy than other existing forms of transit. Here is the link again.

[snoogit]

I'm sorry but to me this is just something I'd expect to see at Disney World, and not in an urban setting.

Its a nice idea, but if you propose it to anyone, thats likely going to be their first impression as well! I don't want to see GR look like a circus, but want it to feel more like a city that is vibrant, and gets along with its neighbors, and doesn't need to be seperated into little amusement park-style "pods" because little jimmy will spill his milk if he rides with another passenger thats not his mommy.

The ultimate system is one that wont require all new parts, LRT and BRT do that. (although I also admit BRT even has a disney-world esque feeling to it, but not nearly as much.)

[dtown]

this doesnt sound like it would work because you would need thousands of cars to transport all the passengers(with a friend or two in the car with them) i think light rail would be the best option for GR

also...think about this; 30 people are riding by themselves and all want to get off at one station..thats alot of cars..you would have to build big stations to hold all theese cars without causing back ups on the rest of the track..to me, that seems like a waste of valuable land in the downtown core

with LRT or BRT all thoose 30 people could be on one car and the station wouldnt have to be huge to only have one or two cars at it at once

just seems like it would be better to me

[prtsupporter]

this doesnt sound like it would work because you would need thousands of cars to transport all the passengers

According to The Rapid Ridership Report, the average weekday ridership for April, 2005 was 22,505. If it continues to increase around 18% every year, it will be around 50,000 per weekday by 2010.

Let's figure that a single hour of "rush hour" accounts for 10% of total daily trips, and let's use the same calculations as on the same page as mentioned above. The demand between 8AM and 9AM for GR would be 5,000 people. Working backwards, we see that 4166 vehicle trips would be needed (1.2 passengers/trip), which equates to 764 PRT vehicles needed (4166 trips / 5.45 trips per vehicle per hour).

For more explanation about PRT capacity, see this Get There Fast page.

think about this; 30 people are riding by themselves and all want to get off at one station..thats alot of cars..you would have to build big stations to hold all theese cars without causing back ups on the rest of the track

But, the 30 people wouldn't arrive at exactly the same time. A 3 berth station could handle 12 vehicles arriving per minute (each berth could handle an arrival every 15 seconds), so 30 vehicles could be handled in two and a half minutes.

Using the numbers from the "Capacity Measures" page again, if 5,000 people are arriving in downtown every hour, 21 people would be arriving every 15 seconds (the time to deboard). Seven 3-berth stations would be able to handle this amount of traffic. There would probably be more than 7 stations, or very popular locations would have stations with more than 3 berths.

with LRT or BRT all thoose 30 people could be on one car and the station wouldnt have to be huge to only have one or two cars at it at once

This page says about PRT: "A typical 3-berth station would require 10' per berth for the platform, plus an extra 10' on the end for the elevator. This gives a total station size of 40' in length, by about 10-12' in width."

Light rail stations for the Phoenix Valley Metro light rail system are "approximately 16 feet wide by 300 feet long". Each light rail vehicle is "approximately 90 feet long", so even a 6-berth PRT station (70 feet) is smaller than the smallest light rail station, since the light rail station would need to be the entire length of at least one car.

PRT stations would be less intrusive than light rail stations.

[dtown]

According to The Rapid Ridership Report, the average weekday ridership for April, 2005 was 22,505. If it continues to increase around 18% every year, it will be around 50,000 per weekday by 2010.

Let's figure that a single hour of "rush hour" accounts for 10% of total daily trips, and let's use the same calculations as on the same page as mentioned above. The demand between 8AM and 9AM for GR would be 5,000 people. Working backwards, we see that 4166 vehicle trips would be needed (1.2 passengers/trip), which equates to 764 PRT vehicles needed (4166 trips / 5.45 trips per vehicle per hour).

For more explanation about PRT capacity, see this Get There Fast page.

But, the 30 people wouldn't arrive at exactly the same time. A 3 berth station could handle 12 vehicles arriving per minute (each berth could handle an arrival every 15 seconds), so 30 vehicles could be handled in two and a half minutes.

Using the numbers from the "Capacity Measures" page again, if 5,000 people are arriving in downtown every hour, 21 people would be arriving every 15 seconds (the time to deboard). Seven 3-berth stations would be able to handle this amount of traffic. There would probably be more than 7 stations, or very popular locations would have stations with more than 3 berths.

This page says about PRT: "A typical 3-berth station would require 10' per berth for the platform, plus an extra 10' on the end for the elevator. This gives a total station size of 40' in length, by about 10-12' in width."

Light rail stations for the Phoenix Valley Metro light rail system are "approximately 16 feet wide by 300 feet long". Each light rail vehicle is "approximately 90 feet long", so even a 6-berth PRT station (70 feet) is smaller than the smallest light rail station, since the light rail station would need to be the entire length of at least one car.

PRT stations would be less intrusive than light rail stations.

oh...im still skeptical about it though

[prtsupporter]

The ultimate system is one that wont require all new parts, LRT and BRT do that.

What does this mean? I'm pretty sure all of the major components in most PRT designs are already used in other situations today.

I don't want to see GR look like a circus, but want it to feel more like a city that is vibrant, and gets along with its neighbors, and doesn't need to be seperated into little amusement park-style "pods" because little jimmy will spill his milk if he rides with another passenger thats not his mommy.

The average number of passengers per automobile trip is 1.1. The automobile is still popular because of it's convenience and point-to-point travel ability. An automated public transit system the has some of the same benefits (plus others like non-stop travel and increased energy efficiency) would cause a city to look like a circus??

[Snowguy716]

PRT wouldn't eliminate cars. But PRT would have several benefits over cars in urban areas: Reduced number of accidents due to running on a captive, grade-separated guideway and automated computer control; increased energy efficiency; non-stop travel to the destination station (no traffic jams); no need to find or pay for parking.

Aren't freeways supposed to be non-stop travel to a destination "station" (intersection)? And we see how pathetically backed up those get. And are we really talking about a PRT system that runs by every neighborhood so that a car isn't needed? Or is it more likely that we will need park and ride systems for less dense areas... meaning the parking fee stays?

I could see the system working as a people mover system like what Detroit has or something... but when those become feasible it's more efficient to have cars that can hold 40-50 people.

[Greedo]

The other disadvantage I see with PRTs is ownership. Most people take care of their cars, because they have a person interest in the vehicle.

A PRT pod removes all ownership responsibilities from the passenger, so they could eat and leave their newspapers and other trash on the pods and the only person who would care is the next passenger.

Granted all public transportation systems run this risk, but at least with mass transit you don't have the privacy that PRTs allow.

[Snowguy716]

Good point. Public transportation should remain public. We all know what people would do if left alone in a "pod" that they didn't own.

[snoogit]

The average number of passengers per automobile trip is 1.1. The automobile is still popular because of it's convenience and point-to-point travel ability. An automated public transit system the has some of the same benefits (plus others like non-stop travel and increased energy efficiency) would cause a city to look like a circus??

The first image that pops into my head when I heard of Personal Rail Transport:

I think I speak for many people when I say they have many similar images pop into their head when they hear of PRT. It just sounds like something you would see at a Cedar Point, or Disney World, not in a city with any sort of dignity.

[prtsupporter]

Aren't freeways supposed to be non-stop travel to a destination "station" (intersection)? And we see how pathetically backed up those get.

I'm not a highway expert, but doesn't this have to do with the buffer zone people need to have around their car to compensate for reaction time, etc? Merging and chaning lanes impacts the buffer zones of all of the vehicles in the near vicinity.

With a fully automated system, the computers have much faster reaction times to events (milliseconds) and have been programmed to generate merge patterns that don't require other vehicles to slow down, etc. One system involves slots where every position on a track that can have a vehicle is a "slot" and the slot is either empty or has a vehicle. Before a vehicle leaves a station, the computer finds a slot that is available for the entire trip, and reserves it. No other vehicles can interfere with that vehicle.

And are we really talking about a PRT system that runs by every neighborhood so that a car isn't needed?

The Wikipedia article mentioned above describes the typical design: "Most systems locate these (stations) about 800 meters (1/2 mi) apart, so that typical maximum walking-distance access is half that, 400 meters (1/4 mile). Average walking distance would be approximately 1/8 mile."

But, yes, in areas of low density outside of the city, it wouldn't make sense to build the infrastructure of the PRT system, so travel to/from those areas would still be by other means.

I could see the system working as a people mover system like what Detroit has or something... but when those become feasible it's more efficient to have cars that can hold 40-50 people.

More efficient how? I already talked about this.

It just sounds like something you would see at a Cedar Point, or Disney World, not in a city with any sort of dignity.

Why does it sound like that? Just because it's unfamiliar?

[Greedo]

Why does it sound like that? Just because it's unfamiliar?

NO, because it looks and sounds like a lame-o carnival ride! Why don't we just make the pods individual tea cups and race them in a circle?

[torgo]

I don't think this would ever work in a zillion years.

Obviously, such a system would need lots of computing horsepower behind it. So what happens when the computer screws up?

Or if you wanted these rail tracks things all over the city, how on earth do you justify the cost of building it? $10 million to build a PRT line that serves a hundred homes? And if you would only have them on the major arterials, then isn't that why we have buses?

And what happens if you have 10,000 cars on the system, but only 4,000 are in use? Wouldn't that require a HUGE place to store the extras?

And if these will be on a seperate grade (i.e. elevated), then wouldn't we be actively taking away from the activity of the street that we strive to create?

And if these things cost $10 million per mile to install, that's not exactly a bargain. Yes, its probably cheaper than running our current highway system, but you couldn't just get rid all the freeways.

We already have personal transportation devices, they're called cars. And we already have the tracks. They're called roads. I'd rather focus my energy on creating walkable, mixed use towns and cities.

[snoogit]

Why does it sound like that? Just because it's unfamiliar?

well in doing a google search, one of the first images that popped up was this:

[prtsupporter]

Obviously, such a system would need lots of computing horsepower behind it. So what happens when the computer screws up?

How would the computer screw up? Hardware failure? If a single node of a redundant system fails, the secondary node takes over and the primary node is repaired when possible... No interruption in service See this paper.

If you're talking about a software problem or logic error... I expect that a system like this would go through enough testing and certification that these kinds of problems would be eliminated by the time it's usable by the public.

The "ULTra" PRT system has been certified by the UK rail safety agency.

Or if you wanted these rail tracks things all over the city, how on earth do you justify the cost of building it? $10 million to build a PRT line that serves a hundred homes? And if you would only have them on the major arterials, then isn't that why we have buses?

As has been mentioned, PRT is most effective and would probably only be built in areas of high enough density.

Buses get stuck in traffic. Buses, like other schedule-based group transit system, require the passenger to wait for the bus and stop everywhere that other passengers get on or off. PRT would be on-demand and provide non-stop travel to the destination station. If buses are sufficient to meet the needs of an area, then PRT isn't needed.

And what happens if you have 10,000 cars on the system, but only 4,000 are in use? Wouldn't that require a HUGE place to store the extras?

Wow, that's a lot of cars. Didn't we already determine that only 764 PRT vehicles would be required to meet the anticipated transit usage in GR in 2010?

Some vehicles would be stored at the stations when not in use. Other vehicles would be stored on "storage guideways", which would just be another guideway rail with a roof, or at an enclosed storage facility, such as the maintenance facility. Since the vehicles are small, the storage facilities don't have to so huge.

Let's say one-third of the vehicles can be stored at the stations. Two thirds, or about 500 in our proposed GR system, need to go somewhere else. If each vehicle is 8 feet long and we use the same logic as here, we would need about 4000 linear feet of guideway, or 2 sections of 2000 linear feet, or ...