Some More Musings on Dualmode versus Singlemode PRT


Dennis Manning

I have read the DM/SM debate pages with much interest. The majority opinion, so far, seems to be that SM can't provide sufficient service for the long run. However, DM advocates all agree that an interim SM period must precede a DM deployment in order to build the network to a size sufficient to warrant the use of DM (quite a bit of disagreement on cost and length of this period), and most DM systems are envisioned to do both SM and DM at some point. This gives rise to three questions:

1. If SM PRT can't do the job. Who will have the staying power to go through the interim SM only period? (It would seem successful SM is a prerequisite for DM)

2. On the other hand, if SM PRT does prove to be successful, how far will it be developed before the DM is blended in?

3. Should a combination DM/SM system come into being, what would be the eventual balance of use between SM/DM?

My take is that SM will develop much further than most see it. However, I think DM is a concept that eventually should be tried. Then there would be a really fascinating period where system operators would have to choose on a continuing basis whether to put expansion money into SM stations or DM ramps or maybe even stations that are a combination. Place your bets :-)

However things turn out, I believe the focus should be to make the operation profitable, and not get bogged down trying solve the problems of the existing transportation system. It changes the emphasis to providing convenience, speed, access, low cost, etc. and away from pollution, energy savings, congestion relief, etc. The former is what the consumer wants, the latter is what planners want. As Peter Drucker said in his book Managing for Results - "Results come from exploiting opportunities, not from solving problems. All one can hope to do with solving problems is to restore normality. Opportunities, meanwhile, go unexploited."

PRT is entrepreneurial and hopefully opportunistic, ITS/AHS is bureaucratic and wrestles with problems.

Dennis Manning has been a transportation engineer with CalTrans for many years and is now retired. He is the Secretary/Treasurer of the Advanced Transit Association and manager of ATRA's website .

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Last modified: April 13, 1998