> The problem with a system like this is that it requires us to throw out the existing system and replace it.
Right, because all horses were put down when trains were invented. And all rails were pulled up when cars were invented. And all roads were removed when, um, helicopters were invented, or something. Clearly any any new technology which isn't interoperable with the old requires the total abandonment of its predecessor. To ensure this, PRT stations will need to have some kind of access control mechanism which ensures that anybody who uses roads or cars is excluded from the system, and vice versa...
Sorry for the sarcasm, but this is an argument that I encounter far too frequently, and it's completely fallacious. Nowhere does it say that building new infrastructure requires the abandonment of the old.
Your second fallacy is the assumption that roads are necessarily "existing" or are in any way cheap.
First, in the next 40 years, the world's urban population will increase by 2-3 billion people. For the most part, the transport infrastructure they will use does not exist yet. Decisions on what that transport infrastructure should be can be based on current best practice rather than what is "existing".
Second, even in existing cities, roads wear out relatively quickly and are potentially more expensive to maintain / replace than PRT infrastructure. The balance of which is more cost-effective to (re-)implement is something that has to be looked at on a case-by-case basis, but is not nearly as straightforward as you suggest.
Third, roads are "cheap" only if you ignore the cost of the "rolling stock" (ie the cars people have to buy to use them), and also assume that the underlying land has no value. Note that this is a tremendous amount of land: between 45% - 55% of the surface area in most cities. PRT costs are generally given as inclusive of the rolling stock, and PRT infrastructure uses about 95% less land area per unit of capacity. In medium- to high-density areas, a full-cost accounting of this typically comes out wildly favourable to PRT.
Its two main drawbacks are that it does not handle crush loading caused by large demand fluxes (just like cars, but unlike trains), and that it is not cost-effective in low-density areas (just like trains, but unlike cars). Its natural niche is as an extension to light rail and subway systems (which can handle crush loads during peaks), serving medium-density areas which the mass transport systems could not economically serve on their own.
Right, because all horses were put down when trains were invented. And all rails were pulled up when cars were invented. And all roads were removed when, um, helicopters were invented, or something. Clearly any any new technology which isn't interoperable with the old requires the total abandonment of its predecessor. To ensure this, PRT stations will need to have some kind of access control mechanism which ensures that anybody who uses roads or cars is excluded from the system, and vice versa...
Sorry for the sarcasm, but this is an argument that I encounter far too frequently, and it's completely fallacious. Nowhere does it say that building new infrastructure requires the abandonment of the old.
Your second fallacy is the assumption that roads are necessarily "existing" or are in any way cheap.
First, in the next 40 years, the world's urban population will increase by 2-3 billion people. For the most part, the transport infrastructure they will use does not exist yet. Decisions on what that transport infrastructure should be can be based on current best practice rather than what is "existing".
Second, even in existing cities, roads wear out relatively quickly and are potentially more expensive to maintain / replace than PRT infrastructure. The balance of which is more cost-effective to (re-)implement is something that has to be looked at on a case-by-case basis, but is not nearly as straightforward as you suggest.
Third, roads are "cheap" only if you ignore the cost of the "rolling stock" (ie the cars people have to buy to use them), and also assume that the underlying land has no value. Note that this is a tremendous amount of land: between 45% - 55% of the surface area in most cities. PRT costs are generally given as inclusive of the rolling stock, and PRT infrastructure uses about 95% less land area per unit of capacity. In medium- to high-density areas, a full-cost accounting of this typically comes out wildly favourable to PRT.
Its two main drawbacks are that it does not handle crush loading caused by large demand fluxes (just like cars, but unlike trains), and that it is not cost-effective in low-density areas (just like trains, but unlike cars). Its natural niche is as an extension to light rail and subway systems (which can handle crush loads during peaks), serving medium-density areas which the mass transport systems could not economically serve on their own.