I've been doing a lot of thinking about the issue of Personal Rapid Transit as of late. As a middle-school nerd, I was fascinated by the ideas of science fiction writers who predicated a world of the future where you could go anywhere you wanted by pneumatic tube or other similar, futurist versions of PRT. As a adult, I'm still fascinated by the concept but realize that it actually doesn't fit with how historical development occurs.
There are two types of development, in terms of how technology develops. The first is linear development, where innovation leads to bigger and better versions of the same thing (e.g., automobiles now versus automobiles in the 1940s). The second is when a disruptive technology undercuts an existing product with a completely different product that serves a similar function (e.g., 3.5" floppy disks versus USB key drives or even CD-ROMs).
Here on Third Rail we often compare PRT to automobile use, because they serve similar functions - carry a few people (who generally know each other) from point A to point B. PRT is generally different from regular transit, which carries a large number of people (who generally don't know each other) from somewhat close to point A to somewhat close to point B. Therefore, I'm comfortable equating PRT with automobile use - people who take PRT are the people who would otherwise drive, but don't want to deal with the hassle of parking, paying insurance, etc.
The point of the argument, then, is this. PRT is not designed to replace mass transit (subways, light rail, and trains). It's designed to replace automobile use.
For PRT to successfully replace automobiles, it would have to be a disruptive technology, meaning it would have to have a major benefit over automobiles that would so undercut the automobile market that everyone would switch to PRT in a short period of time.
The reality is that PRT does not and cannot do this -- and the reason is that the linear development of automobiles will negate the need for PRT.
We know that automobile manufacturers are already working on systems to remove a human driver from the equation. In twenty to thirty years, people won't need to drive their own cars - they'll be able to push a button on their dashboard and have them driven for them.
Which basically means, automobiles will ultimately develop into what current activists are calling PRT. And they're better suited to do so. We don't need to construct obtrusive elevated rails for PRT. We already have millions of miles of rubber streets which are prepared to handle the traffic. We already have auto manufacturers who can build the cars to individual specifications. We already have federal and state funding massive focused on paying for roads and street infrastructure.
All-in-all, we already have a system designed for PRT. It's just that PRT won't be in the form of elevated rail and individualized cars, because it won't be necessary. PRT doesn't have the added benefit to be a disruptive technology; its functionality will simply be incorporated into the automobile, bringing all the benefits of PRT without a major overhaul of the existing system.
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amg | 02:06 PM |
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Unfortunately your argument fails straight away.
PRT is designed to replace both the automobile and mass transit, by taking the best aspects of both and creating something with more advantages than either.
PRT is a disruptive technology - because it is perfectly possible to construct and operate it today. All it needs is a little willpower and money and you can have a 100% functioning system that will provide a very effective and efficient transportation system for the same cash people are more willing to spend on costly and unprofitable mass transportation and highway networks.
Why wait another two decades or so for automobile manufacturers to try and reinvent something that could be up and running in less than three years, and work better too?
Hold your horses, DA. Even if we thought it was a good idea, it's not like we have the money to buy it. Best take your snake oil to Brockville, Ogdenville or North Haverbrook. By gum, you can put them on the map!
Because, DA, what you're missing is the infrastructure investment. For PRT to be a disruptive technology, it would have to be less costly and appeal to the vast majority of people. Unless you plan on implementing a country-wide network of PRT systems, people will not abandon their automobiles, as they want to be able to drive to places not accessible by PRT. And that's not feasible, as we've already poured billions of dollars into roadway funds. If people aren't willing to sell their cars, there's no way PRT can be a replacement for them (nor should it be, anyway, because it makes no economic sense to use it for long-distance travel). Ipso facto, PRT is not a replacement for the automobile.
And the point you're missing is that it won't ultimately be profitable, because to make it profitable you'd have to have such a high per-ride cost (once real construction costs are figured in) that people would rather drive. For moving small numbers of people, cars are more efficient; for moving large numbers of people, mass transit is more efficient.
Sorry to burst your bubble, but PRT doesn't fit into the picture.
The question is not that of car ownership, but car use. And in fact using the most appropriate form of transport depending on the trip you wish to make.
If a local PRT system is constructed to provide blanket coverage of a specific urban area, then within that area people will have a choice between continuing to use their automobiles, existing mass transit system or the new PRT system.
The existing proposed PRT systems have been designed to be relatively cheap to construct and operate within very specific parameters, and thus would be able to offer a more of a profit and a quicker return on investment that traditional transit schemes.
You might have poured billions of dollars into roadway funds, but has that been money well spent? And is anyone making a profit on them?
If you had researched the existing PRT proposals, you will also have found that their business plans allow for no public investment at all, and in fact favor funding entirely by private investors.
If PRT fares are set at a level that both attracts customers and makes a profit, there's no reason why it can't be used for either short-, medium- or long-distance travel, given the establishment of a suitable network.
The definitive discussion of why PRT is "a solution in search of a problem" (even if the concept didn't have dozens of "fatal flaws") located at:
www.lightrailnow.org 3rd item on page.
I see you and I are on similar wavelengths here. PRT, as you say, is not disruptive enough to warrant the investment it needs to be a plus in the long term. The evolutionary approach you line out, increasing use of automation in the cars themselves, is in fact a more efficient use of existing technology than PRT's elevated track would provide. The other problem with PRT is that it requires a well distributed network in order to become feasable to most transit customers, and that only comes after massive investment. Any transit system that hopes to compete with the automobile has to do two things:
- Come within very easy walking distance of their front door
- Go within very easy walking distance of where they want to go
In order to effectively compete with the car, you're going to have to replicate the existing road network as an above-grade track. All you are doing is replicating, as in duplicate, as in double the cost of, the existing road network just for a second class of vehicle that is run by a computer. While if $5bn were to fall out of the sky onto a prospective PRT developer, it could be done with today's technology, by the time the thing gets completely built we'll be a lot closer to the drive-by-computer systems that an
at grade PRT system would allow.
An at-grade system, call it a computer-taxi service if you must, can be deployed in stages and can easilly piggy back onto existing highway funding. Before the computer cars are here, we can start embedding sensors into the highway and arterial streets to scan for passing cars. By the time the cars get here we can have some really nice data streams for either the DoT's or corporates to massage into a salable product for avoiding congestion. That by itself will help. Once the drive-by-computer systems really come online, we'll have a nice data stream for them to dip into to create the exact same efficiencies the PRT systems would. And realisticly speaking, at about the same time the PRT systems would be getting to THEIR peak efficiencies (i.e. 15-30 years in the future).
I think your arguments about PRT vs Cars are quite interesting. That said there are some problems about a automated Car system. Your right there have been some attempts at ‘systems to remove a human driver from the equation’ these are currently up market cruse controls ( BMW have an experimental car can even over take).
Firstly PRT has an entirely separate network – this is in fact building cheap new travel capacity into the urban grid. With an Automated Car system your not getting any new capacity. PRT gets a big speed boost by not having junctions ( lines cross over each other), automated cars would not get this benefit. Trying to run all cars on a PRT like mini monorail (called dual mode) would require a *24 increase in track investment (PRT cars are very low weight).
Secondly automated cars would have to share the road with normal drivers. This would make the whole computation process incredibly difficult. So where as it make take 30-50 years to build a computer capable of sharing the road with human drivers. There are some cyber cars which operate with pedestrians present but they do this by going very very slowly. A true cyber car would have to see signs,traffic lights.. Having separate elevated tracks and controlling the kinds of vehicles which run on it means you can have today what an automated car system will have tomorrow.
Thirdly having a separate track means you can constantly supply electricity. This can be supplied by a number of means ( coal, gas, wind, nuclear e.t.c). The automated car would still have to run on oil ( or be a disruptive technology). The automated car would have to survive in an environment of badly driven SUVs and so have to be big, bulky and so use more fuel ( of any sort).
So automated cars don’t seem to offer any chance of reducing travel times, reducing pollution, reducing cost , or do anything for congestion.
Think of it this way.
Your want to build not a city but a single tall skyscraper.
Method A. you install a device called a lift. It operates on a dedicated track working between stations(floors). The ‘lift’ is shared with small number of other people . It operates entirely automatically. All the passenger has to do is select the floor they want. You have 6 or 8 or more lifts depending upon the number of floors. Lifts only stop when someone wants to get on or off. Passengers summon a lift by pressing a button.
Method B. You install a device called a light rail lift. This is similar to Method A. except for safety reasons it is ‘driven’ by a driver. To save costs and increase efficiency you only have one light rail lift per building. Each light rail lift carries 80-100 people. This lift operates to a fixed schedule stopping at every floor. It takes 20 –40 mins to do a round trip. People have to walk if the professional lift driver is ill or the lift is out of service.
Method C. Car. You surround the building in a large concrete spiral. Its heavy noisy and expensive but people drive up all the floors and stop directly at their office. 50% of your office space is not taken up by parking. At peak times you can get stuck in your car as limited spiral road width is taken up by every increasingly big cars. The good news is the cost of the sprial road is paid for by the government.
Method D. Automated Car. Like Method C but you have laptops running windows drive up the big spiral.
Which one would you pick ? Make the skyscraper taller and turn it on its side. Suddenly method A becomes all ‘futuristic and unworkable’.
I’m appalled at the lack of imagination.
