Where did all the PRTs go?

PRT, or Personal Rapid Transit, a system where a small automated vehicle will take you from the origin station to the destination station non-stop, seems like the future of public transit but have existed for a long time in concept, prototype, and product. They simply haven't taken off.

There are a lot of sources on the history of the PRT, but since they were written by people who invested heavily in them, they are slightly biased. If you want a comprehensive history, check out Some Lessons from the History of the PRT.

The first PRTs were conceptualized in the 1950s when automatic control technology matured enough for PRTs to become technologically feasible. Numerous prototypes were developed in the 60s, and the Urban Mass Transportation Administration (precursor to the DOT) conducted numerous studies assessing the benefits of PRTs. The resulting HUD studies (some done at Stanford) developed numerous ideas for the future of transportation (which were listed in the 1968 report to Lyndon Johnson) and supported them with convincing urban movement simulations.

In late 1970, new PRT system in Morgantown, the site for University of West Virginia, was proposed. Developers put an unrealistic goal of having the system complete by the October 1972 (politically driven). "As a result mistakes were made that caused the system and its costs grow by a factor of four, which was almost the only fact reported by the press. The result was a major black eye to PRT generally and a loss of confidence in PRT in Congress as well as in foreign governments."

The Morgantown People Mover nevertheless was completed and opened for passenger service in 1975. "While some do not think it is a "true" PRT since the vehicles and guideway are so large and not all of the rides are non-stop from the orgin to the destination... Certainly, it is as close to a "true" PRT as has been achieved in the U.S. to date."

"September 1974 was a turning point for PRT development. People interested in PRT could no longer get federal grants, yet the interest would not die because an unmet need existed and it was well understood by people working on PRT that the reason was not technical unfeasibility but turf protection."

Conclusion

While many reasons can be attributed the failure of PRT, technical limitations is not one of them. However, the perception of technical limitations could have been a factor in the minds of decision makers and investors (this could explain why light rails are being developed in the 90s and 00s in the US). The designers and engineers heavily invested in PRT seem to blame politics and the lobbying power of the automotive industry as the main culprit, but could that have been the case for every single developed country in the world? Perhaps the Catch 22 of Infrastructure sums it up best: "The industry only builds what is already being demanded by the public authorities, and the public authorities only demands what is already being built by the industry." I once heard a professor in Biomimetics say that evolution is far from optimal. That seems to be the case for transportation too.

Dualmode

"Dualmode transportation concepts feature vehicles that can be driven on conventional streets and can also operate on a high speed automated, usually electrified, guideway under computer control" (More in-depth discussion here). The concept has been discussed for ages and simulations have been proving their benefits over the last few decades. However, prototypes have been developed recently, and the most refined of which may be the Danish RUF (acronym for Rapid, Urban, Flexible).

Vehicles can be personally owned (cars) or publicly owned (buses), and are 100% electric. CNN has a overview article from 2001 that doesn't mention any of the other failed attempts at PRT in the past. Personally I see Dualmode facing the same infrastructure problems as PRT and never hitting critical mass. Railways would have to be laid out before cars become rail compliant, but enough cars would have to be rail compliant for railways to be justified. I think Automated Highway Systems has a lower barrier to entry than Dualmode, something I'm going to investigate next.