PRT car designed by Zagato, unveiled recently at the World Future Energy Summit.
The designers of Masdar City, Abu Dhabi's new post-petroleum city, are not bound by the usual set of rules and constraints. Money is not really an issue, and the political leadership is always willing to try out innovative ideas that the rest of the world regards as unproven, unorthodox or just plain fantasy.
One of them is PRT, personal rapid transit, a system of transportation featuring compact, driver-less "podcars." In Masdar, where the streets will be entirely free of automobiles, a network of these compact electric taxis will provide clean and quiet transportation to the city's residents, as well as commuters. The first PRT cars are set to begin running later this year. Admittedly intrigued, TreeHugger sat down with one of the system's designers recently at the World Future Energy Summit in Abu Dhabi to hear more about the project.
Luca Guala is a transportation planner with Systematica, the firm that drew up the plans for Masdar's PRT system. According to Guala, Systematica's planners spent months working with Foster + Partners, the city's architectural planners, to integrate sustainable transport solutions into the city's design.
In addition to PRT, he says, a light rail line will snake through Masdar, most likely running between Abu Dhabi's international airport and the city center, some 20 km away. Although no cars will be allowed into Masdar City, nine multi-story parking lots will be scattered along its perimeter. Residents, commuters, visitors and buses will all have dedicated parking spots there, allowing them to own and use cars outside the city walls.
TreeHugger: Would it be fair to describe PRT as a system of transportation which combines the sustainability of a light rail with the convenience of the private car?
Guala: The PRT system in Masdar City will be a complementary system to the light rail, which will cross the city. PRT is not a system that can move huge masses of people, for that you need a light rail or a metro. A metro can move 60,000 passengers per hour — that's equal to about 20 lanes of highway.
One of the differences between car travel and public transportation is the experience of traveling at rush hour. On the highway, you may be stuck, but you're sitting in the comfort and privacy of your car. Meanwhile, on the subway you're in motion, be you're packed in with hundreds of other people.
Masdar City's PRT system will have no rush hour congestion. When the computer sees that the network is approaching capacity, it will simply not allow cars to leave stations. This will not happen frequently, and when it does happen, passengers will be asked to wait for a few minutes.
Generally we foresee no more than a three minutes wait for passengers at a station, but there may be special occasions when the wait time is longer. If the Rolling Stones have a concert in Masdar, an event like that is bound to create congestion, and you may have to wait for more than three minutes. But we do not expect anything like that on a normal workday morning. You won't be late to work in Masdar City because of traffic.
The PRT vehicles will travel at speeds of approximately 7 meters per second, with the longest routes in the city being perhaps 2.5 km. So let's say you reach a station, wait maybe 1.5 minutes for your car to arrive, travel for 5 minutes if your destination is relatively far away, and then exit the station, which will take around a minute. So the longest trips in the city will be around 7, perhaps 10 minutes long.
PRT cars will move along rights of way, approximately 6 meters under street level. [Masdar City's streets will be raised off the ground, but buildings will be built at ground level, with the first couple of stories serving as basements and space for technical equipment.]
We decided not to build elevated tracks in Masdar. Elevated tracks would put the cars between the first and second floors of buildings, and no one wants to see cars, even silent ones, zooming past their window. Plus a spaghetti grid network might not be so nice to look at from below, and could become a real visual issue in the city's narrow streets.
TH: What will it be like to travel on the PRT system in Masdar?
Guala: Passengers would descend a flight of stairs or an elevator to the station - perhaps an escalator in larger stations, but we decided to use only a few escalators, since they are more energy intensive. Elevators are necessary for the mobility disabled.
You will swipe a smart card through a machine, and a welcome message will appear. One option is that the system will recognize you and greet you personally: "Good morning, where do you want to go today?" Perhaps the system will remember your usual path, and offer it to you as an option. After you click on your destination, the system will say something like, "Your car is arriving in 2 minutes at platform number 3." You may have to stand on a line, and you will be able to identify your car by its number.
The second option is that you will enter your destination into the system when you are already sitting inside a car.
Initially, the system will be very simple, with only a couple of stations. During this period, the system will function kind of like an elevator — you press a button and go to the third floor. Think of it as a horizontal lift. Later on it will be more sophisticated, and passengers will be able to get within 100 meters of any destination.
The cars will not run on tracks, but will operate within a kind of grid network, and take the shortest paths to get where they need to be. The cars will have wheels, and will be battery powered.
TH: What kind of history does PRT have in practice?
Guala: PRT systems have had problems with things like cost overruns in the past. Few systems have actually been fully built and implemented. The one in Morgantown, West Virginia is the only one currently in existence. There is also one under construction in Heathrow airport in London.
Morgantown was built some 30 years ago, and was extremely expensive. They had to invent many of the components of the system from scratch, including the computer system. It was a prototype in every sense. Today, the computerization aspect is almost trivial. If your laptop had been around back then, it would have been powerful enough to implement Morgantown's control system.
The only pure PRT systems going up today are the ones in Masdar and Heathrow — different systems which work according to similar logic. One of the companies involved in developing the system here in Masdar, 2getthere, has developed a system for transporting freight containers in the Rotterdam port in the Netherlands that works exactly like PRT. In Masdar, cargo will also be transported by PRT, using special freight cars.
TH: How was the system planned out?
Guala: We used the same "predict and provide" models that are used to plan new roads. We had rough data about things like population size, arrival times, etc. We ran a few models and found that a few areas came out congested, so we interacted with the town planners and tried to get the best placement for various land uses.
A schematic representation of a PRT system vs. monorail. Image courtesy of Systematica.
For example, something like a conference center, which attracts a lot of people all at once, could become a local generator of congestion. So we said: let's move it slightly to the side. The end result is a large patchwork of land uses, with none of the city's districts clearly defined by a single use, like offices, residential and so on. That is ideal from a transit perspective, because it diffuses demand [traffic.]
In Masdar, you will be able to live very close to where you work. The districts will be in use at all hours. There will be nodes of activity at the intersections of routes, but the trick is that each nodes does not serve people doing the same thing and traveling at the same time — thus no traffic is created.
TH: How did the specific cultural context in Abu Dhabi affect the planning?
Guala: Well, I am Italian. I bring with me a certain cultural model — namely the good parts of the Italian city. I think it is possible to apply the Italian city model in Abu Dhabi to a certain extent. But you can't just transplant something to another culture and make it work.
The classic Arabic city has many similarities to the Italian city. There was a common way of living in the Mediterranean Basin, in Christian as well as Muslim areas. From a town planner's perspective, the classic Arabic "medina" [dense Middle Eastern city with narrow streets and interior courtyards] and Venice are similar. Masdar City takes its inspiration more from the Arabic medina than from the Italian city.
There are other cultural preferences involved here as well. People in Europe are used to taking public transport. It's not necessarily like that here. Plus there is more sensitivity here to the privacy of the family, which led us to suggest a different kind of system, more suited to the local cultural context.
TH: Is PRT cost-efficient?
Guala: This will be an expensive system. It has to be that way, because it's a prototype. From an energy perspective it's extremely cost-efficient, which is what Masdar [the Masdar Initiative is the corporate body that is building Masdar City] wants. The maintenance of a system like this is more expensive than that of a system based on buses, but the level of service is absolutely unreachable by other forms of public transportation.
The huge advantage of PRT is that it is "on demand," including during off-peak hours. During peak hours, PRT is less efficient than public transport. But PRT is a 24-hour service, just as available during off-peak hours as it is during peak hours. This is much more efficient than running empty buses all night. There are advantages in terms of personal security as well — no long waits in the middle of the night, for example.
I don't really know about the financial aspects in detail, it's not really part of our job as planners. It is technically possible to cover costs with ticket fees. A fee roughly equivalent to the cost of a taxi ride would cover the costs of the system. There is a huge investment cost in a system like this, but after it is prototyped, the costs will come down. The actual cost of PRT is lower than the costs for a light rail of the same capacity.
TH: What kind of prospects are there for PRT in other places?
Guala: There is a lot of interest in PRT right now, especially in new developments. In existing cities it's a bit trickier to make it work. The optimum place for a system like PRT could be in smaller towns and in contained, controlled environments, like hospitals, universities, new business districts, places like that.