. . .
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
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 <firstname.lastname@example.org>:
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.
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.
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