PONDERING THE 3D REALITIES OF PRT

On September 24, much of the world was thrilled to hear Pope Frances tell the USA to think globally about the impacts of its greed and wars. The PRT world was also buzzed by a NPR (National Public Radio) report on PRT possibilities with an impressive interview with Mike Lester of Taxi 2000.

Explaining PRT and its potential benefits to the general public will no doubt start many productive conversations from coast to coast and overseas as well. The balanced conclusion of reporter Joe Palca’s story held up a countering view from a Minnesota official: PRT is an idea whose time has come and, with smart cars in smart cities, gone. The main culprit is the cost and offensiveness of elevated guideways, intersections and station.

Elevated, Shmelevated

Elevated guideways were highlighted upfront by Lester as a major plus. They free vehicle movements from the clutter and danger of street traffic. They overcome the friction of space. Passengers ride faster and safer.

  

However, the onset of automated road vehicles is creating new solutions. Much of the promise of PRT is that it satisfies local circulation and connection needs. Future next-gen roborcars will be able to do this without exclusive guideways. 

Fixed infrastructure makes up about 70% of PRT capital -- even with elevated guideways that are cheap compared to LRT.  So removing them from a mobility service plan is a big thing. It changes the business model dramatically.

For longer trips, exclusive guideways are needed, but PRT must walk before it runs. Ten- or twenty-station networks were considered within technological reach by MTI’s study team last year.  Why? Because Vectus in Suncheon and 2getthere in Masdar both have only two stations -- not networks at all, let alone complex ones. Ultra at Heathrow has three. Morgantown has five -- where on-demand scheduling and fleet management start to get a little complex.

The problems, costs and non-financial “externalities” (violations of privacy, noise, droppings, shade, blockage of views, etc.) of elevated guideways are real. PRT promoters do themselves a disfavor to minimize or ignore them.

Think 3D

Presenting PRT infrastructure as elevated and only elevated ignores the fact that Masdar isn’t elevated at all.  Parts of Heathrow and Morgantown are at grade. Most metros and older LRTs move up and down in 3D reality - with underground, at grade and elevated sections.

PRT is no different. Certainly it can and in many places should be elevated, but it can be even cheaper at grade - enhanced by bunker-like earthwork, plantings and smarter and smarter security systems. In pretty neighborhoods where real people live and shop and walk and where buildings are close together, the expense of tunneling may be quite justified.

Guideways have vertical dimensionality.

In the end, the future of PRT will not be decided by the optimality of the gadgetbahn, but by the sensitivities and lifestyle preferences of three-dimensional neighbors and lawyers.