Personal Rapid Transit (PRT)
Construction
Intro How it Works  Construction   Economics  Point-To-Point Transport  Capacity   Concerns  PRT and the Environment SF Bay Area Further Information

Construction

. . .

PRT construction is far less disruptive than putting in new sewers or resurfacing the streets.  Again, light is the key concept.  Guideway construction is easy compared to LRT or BART because the parts are smaller and lighter.  A hole is dug for the supporting pole.  The pole is inserted.  The track is laid across the top and a wiring crew hooks up the power.  Installation is straight forward with minimum disruption to normal activity in the area. The support posts and 60-ft. guideway sections install easily.  Modular manufacturing makes guideway components both inexpensive and simple to interconnect.  This leads to a system that is affordable to modify/expand/re-use as needed.

Ports (stations) can be tiny, modular and easily sited almost anywhere! Minimal land requirements for ports and guideway supports reduce conflicts with existing infrastructure: underground utilities (water, sewer, storm drains, gas, electric, cable TV, telephone, fiber optic cables), trees, private property rights, sidewalks, etc.

Here's the bad news from Charl du Toit <charl@ihug.co.nz>:

Foundation engineering is an inexact science because nature does not play according to nice uniform rules.  On the same street there will be half a dozen different soil conditions.  The worst will be found right where you need to put the footing of a load-bearing pylon. One of the reasons for this is that everybody who has built around the place before, has avoided the spot because it's too difficult to build on.

Generally foundation engineers are hugely conservative because no one thanks them for cutting 0.1 cubic meter of concrete out of a footing if there is a chance the building cracks as a result. A mass-produced system such as you envisage would have to cater for the lowest common denominator along the route as well - you would hardly do an individual design for each support pole. So unfortunately you end up with a bigger and more expensive solution than you really need.

In the urban environment as you point out there is the complication of underground services. These are always where you don't want them, and never where the utility company says they should be. There is no way around the problem - literally. You would have to find and identify services all along the route. This is not trivial; a road widening project I was involved with used 35% of the total budget for services relocation. In your scenario this cost could easily exceed the foundation costs.

Here's what you would do:

1. Choose single-pole footings, better in the urban environment because you have less chance of hitting a service.

2. Along the route, you would go along to all the utility companies, and regional services authorities, and the local municipal authority, and get service plans.

3. Get a service detection specialist to physically walk the line, marking services encountered. They use several methods of detection, including metal detectors and subsurface radar. The more sophisticated the method, the more they charge.

4. Dig trial pits at each pylon to locate services. It's better to break the service at this point and have time to plan a fix, ahead of your main  construction.  I have tried an innovative waterjet-powered method which is non-destructive and seems more promising than the digger bucket method of finding stuff underground.

5. Report back to the service owner on what you have found.  Then eat up whatever preposterous demands they make regarding protection of their service (never mind that it is in the wrong place).  Often they will not permit any structure to built over them, and the service will have to be moved.  Generally the utility operator will not permit you to touch the service, and will charge you whatever they feel like to do it on your behalf.  They also do not operate on the same timescale as you do. If it is not possible to move the service, you have to design a costly structure to bridge it, including allowance for future access to it.

6. Cities require building permits for this kind of structure, so you would have to present the final design for approval.  This generally would be subject to public consultation.  If you thought the utilities were bad, try addressing a public meeting consisting solely of those who are there to stop you building something in front of their bedroom window.  When you've changed the design to suit everybody you will know for the first time what your final guideway cost is likely to be.


About Us || Contact Us