There are reasons that PRT has not gone far in this country. PRT can probably be a good solution for a self-contained activity center like a big mall, where it would function like a big sideways elevator. But outside of that narrow application it's hard to see how it can make sense.

It has potential advantages compared to cars -- it's electric (non-polluting), it could theoretically have high capacity if it manages its pod thingies effectively, and it's bound to be safer -- but it's basically a solution to mass transit that aims to replicate the utility of cars. It has the downside of requiring intrusive overhead structures everywhere, as well as space for loading stations.

But the biggest challenges are these: that the road system provides complete network access, and most of the costs of the car system are borne privately. People put a ton of their own money into the car system, buying cars, operating and fixing them, and paying for insurance. (People also absorb the external effects of the car system, including many deaths and the pedestrian-free landscape that so many live in today). And having paid for all this, people are heavily invested in the system. They like being in their own car with their own music and their own mess.

The biggest effect of a PRT system would be to shift all of these costs from the private column to the public one. It would require a *massive* public investment to achieve a network sufficient to provide a critical mass of destinations to allow a neighborhood or city to be free of supporting two sets of expensive infrastructure that deliver basically the same utility. When we can't find the will to pay to keep our streets and highways from crumbling, is it reasonable to assume we could afford the cost of building and financing yet another parallel transportation system on top of the old one? Especially when the street system will remain our primary means for walking and biking and shopping and moving freight for as long as we can look out? If we can find the money, shouldn't we be putting it into making our streets work for all of those things rather than abandoning them for an even more socially isolated high-tech future?

I'm still trying to figure out the relationship of the WVU-Morgantown PRT and "two decades". Maybe that date reflects completion of the inter-campus system?

In 1968, 42 years ago, Boeing and UMTA posters outside my newly-built Towers Dorm declared that the PRT was coming soon!! Apparently, it took longer than expected ...

The system was designed to replace both a fleet of diesel buses that moved students between two core campuses AND to reduce the need for parking at both locations. Based on my last visit to the area, I'd say it's worked in some ways (parking is restricted; dorm residents have easy access to campuses), not others. Absence of strong land use restrictions has compromised its utility.

It's a gimmick concept. In an existing urban setting there are so many flaws it's almost not worth the effort to debunk. Starting with capacity, the potential for choke points, the difficulty of emergency egress from PRT vehicles unless you have a walkway their entire length (which you might have to)....

As the article allude, it can work in certain places. Theme parks are good because PRT can be fun, it's inherent inefficiencies are lessed by the fact that people tend to move in groups rather than individually, and there aren't competing transportation choices except walking.

@Rob Fellows

"Replicating the utility of cars" is way down the list of PRT features. In addition to the electric/non-polluting advantage, the other main reasons so many people are getting interested in it are 1) automation means potential of 24/7 operation if desired, 2) high energy efficiency, in that there is low vehicle weight per seat, and pods only move when needed, 3) high degree of accessibility if stations are placed close together, combined with on-demand service.

You're leaping to the conclusion that planners -would- try to put PRT everywhere. Maybe you're even assuming PRT would displace LRT and bus. Gung-ho PRT advocates would want that, but they don't set policy.

It's much more realistic that a PRT technology that becomes proven would be deployed in niches as a complement to rail and bus. Imagine sections of the city that need rapid transit, but don't have the densities or surface ROW to make light rail economically feasible. A PRT system -could- do it at a realistic cost. With the right cosmetic design an elevated system might even be aesthetically attractive.

Land use-wise, I think PRT in the toolbox gives us another option.

And if you go to Morgantown, you're going to find their PRT is not socially isolating.

Well, ignoring the fact that Disney World is thousands of miles away from Anaheim, California, this is an issue that Walt Disney himself thought a lot about. Anyone who wants to see a real urban planning visionary pitch his scheme should watch Disney's video about (the original) EPCOT. The first of three parts is here (if this link works). It really gets into the meat of it in the second part.

What Disney realized, and which few others seem to have grasped in the intervening 35 years, is that it's very difficult to graft such a transit scheme onto an existing city. Disney's solution was to design an entire city, EPCOT, around the transit plan. That's fine if you, like Disney, own all the land. It's much more difficult to impose such a plan on individual property owners without seriously disregarding the US Constitution.

Disney died only months after this film was made, and EPCOT was never built. It would have been a fascinating experiment - and it would have been done entirely with private money.

Well, the "a href" link didn't work. Part one is here:

http://www.youtube.com/watch?v=dkT2iLetCTc

Heathrow is about to come on line with a PRT to service the parking garages and terminals. So within a year we'll know whether this technology is just a gimmick or worth building anywhere else.

As has been mentioned the small tracks can be an issue if the cars are hung from them, or wrap around it like a monorail, no egress in case of fire, but the Ultra system is mounted on a flat bed, so that's not a problem.

But as you say, the up front cost of building a duplicate to roads has been the major objection.

Also you forgot to mention that even though switching from personally owned to cars to a PRT system is expensive, the benefit is that for a PRT system, the cars are shared and that instead of paying for parking, and parking garages, the track and stations themselves are the storage locations for the cars.

Still a dense city like NYC, a beach front city like Miami could build a PRT system to fix some of their transportation costs for less than adding more roads, or tunnels, or elevated Light Rail.

http://www.xootr.com/kick-scooter_mg.html

http://www.segway.com/

The flat-guideway planned at Heathrow (if I'm understanding that correctly GaryP) is completely different from the dreamer version of PRT. It would basically be an "el" with small routable cars.

Presumably they'll have fairly large stations with plenty of time for people to load/unload without holding thigs up. Some people travel with (apparently) half their possessions, and they can't be allowed to hold things up. Other than that factor, the sort of system this appears to be seems appropriate for airports...Heathrow in particular with its dispersed functional areas vs. mostly centralized functions at Sea-Tac for example. Airports transit doesn't compete with other systems, people often travel together vs. individually, the airport owns all the land, etc.

I haven't been to Morgantown but I have seen it described as not PRT but GRT -- group rapid transit. Their cars are not the tiny pods for individual transport envisioned for PRT but much larger cars built to accommodate small groups. Think elevators. Thus, as Wiseline noted, it's not socially isolating, as real PRT could be.

It's a gimmick concept. In an existing urban setting there are so many flaws it's almost not worth the effort to debunk. Starting with capacity, the potential for choke points, the difficulty of emergency egress from PRT vehicles unless you have a walkway their entire length (which you might have to)....

As the article allude, it can work in certain places. Theme parks are good because PRT can be fun, it's inherent inefficiencies are lessed by the fact that people tend to move in groups rather than individually, and there aren't competing transportation choices except walking..

And cars average less than 1.7 people per car because they travel in groups, right?

How many people have suffered serious harm from being stuck in an elevated vehicle that didn't have a safety walkway? Modern vehicles such as the PRT don't have much combustible material and to the extent they do modern fire-suppression on-board equipment keeps any danger to a minimum.

The capacity is limited by the number of lines in the grid and the number of vehicles. Saying that PRT doesn't have capacity equal to a subway and therefore shouldn't be considered, would be like saying city streets don't have the capacity of a freeway and therefore not worthwhile.

The loading spaces will be offline and won't hold up other vehicles (I do wish they didn't call them Pods)

I'm not sold on PRT but find the red herring arguments counterproductive.

I don't support cars, or even drive, regardless of my advocacy for 99.

The safety measures don't have to make sense. If I have it right, it's US law for any elevated track system. US safety requirements are often way overboard, often lopsided between one vehicle type and another, reflecting poential litigation....the result is that cars can drive at deadly speeds three feet apart in opposite directions, or without guardrails on mountain roads, but public transit is regulated to the nth degree.

Capacity with PRT would be limited on a per-line basis. A rail system with (for example) a capacty of 500 passengers and headways of thee minutes can tranport 10,000 people per hour past a given point, each way. (Many lines do multiples of that of course) I find it very unlikely that a PRT system would do even a large fraction of that. There's no way of having any real idea, because no serious study has been done on anything with significant capacity (so I gather), particularly under US regulations.

So far you haven't identified any red herrings. You'd have an easier time looking at the BS put forth by many PRT advocates. They put out blatantly false pictures of tiny overhead structures and cars that look huge in closeups but look tiny in street renderings. Some even forget the absolutely mandatory need for stairs and elevators at every station with elevated platforms in the US.

Another technology to throw into the alternatives analysis for future urban transportation systems is the combination of privately owned, electric, battery-powered automobiles operating on public streets under automated control. This technology may simply evolve into existence whether we like it or not, beginning with luxury cars.

Electric cars are now a U.S. national priority with lots of government support.

The automation part is being actively pursued by both governments and by segments of the automobile industry, most notably at the moment, Volvo, which is already selling cars with automatic braking when something or someone is detected in the road ahead. See the video at http://ow.ly/2G7yK.

Spoiler alert: there's also nearby to the video I cite an amusing video of a related system not working properly in a vehicle braking demonstration for media. But I happen to think bugs in automatic braking and lane keeping will be worked out and the systems will move into mass market electric cars in the years ahead, leaving PRT systems a specialized application for reasons Rob Fellows describes in the first comment.

I doubt automated cars will exist on streets in our lifetimes. The difficulty of a system that can overcome the chaos of streets at a near-perfect rate is too great.

Freeways are much simpler. No random entrances, no pedestrians, etc. Even then, any initial automated systems will presumably by on barrier-separated lanes at least initially.

This is the future! I have been dreaming of this for years and I am thrilled that SOMEONE is finally putting the pieces togeather. When fully implemented this type of system will; increse the capacity of our roadways two or three times, do away with the expence of road signage, traffic cops, drunk driving, traffic jams. Mostly eliminate private vehicles and have your transport needs perfectly taylored to, on a day by day basis. Redefine our experiace of travel.
Bring it on.