Personal Rapid Transit: Driverless Pods of the (Retro) Future

in #transportation2 years ago

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The future of transportation was a lot of things before it was driverless cars. Many of them more or less the same concept, but designed around the limitations of that era. PRT, or Personal Rapid Transit was principally an attempt to bring driverless public transport to the masses in a form factor similar to a taxi.

The advantages were numerous on paper. Railways need to be able to support the entire weight of the train at any point along the track. So, elevated rail has to be built to a very durable standard, which costs a tremendous sum per mile of elevated track.

This is not (necessarily) true for PRT: The train, in this case, is chopped up into dozens or hundreds of bite-sized four person pods. The track can then be built to support the weight of the pods, which will be distributed across the whole network.

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I said “network” rather than “loop” or “line” because PRT pods also differ from trains in that they can take you almost directly to your destination. The track branches off as needed so pods can go to specific destinations, which don’t have to be on a main loop like they do with light rail.

The pods can also take a short detour off the main track to stop for passengers at PRT stations, so they don’t hold up other pods, which are free to pass on by. The track can be standard elevated rail, even overhead rail with the pods suspended from it as with the Skytran concept, but most often it’s just a guideway and the pods move along on regular pneumatic tires.

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The relatively lightweight, insubstantial track infrastructure makes it possible to integrate PRT into urban centers where (for example) light rail or a more traditional suspended train would be too obtrusive. This has made PRT popular in a few niches like corporate campuses, colleges and airports, where a full blown train would be overkill and occupy too much space.

PRT as a concept has been around since the sixties. Most people’s first, and maybe only, experience with PRT was riding the Disney World Transit Authority People Mover. It was among the first PRT systems actually built and put into regular operation.


Relatively primitive pods, but the propulsion system is purely magnetic with no moving parts except the pod wheels, which are unpowered. The track itself is essentially a linear motor, which cut down on wear and tear so much that it’s among the park’s most reliable systems, all these decades later.

This system was also meant to be the sole public transit solution for Epcot, in its original form as Walt Envisioned it. You can see the elevated tracks in any of the models commonly featured in Youtube documentaries about Epcot. Cars were not to be permitted within city limits.


The 70s film Logan’s Run also depicted PRT as the sole form of public transit within the domed city where much of the narrative takes place. It was a popular idea back then, which explains in part how the Morgantown PRT got built.

Developed by Alden StaRRcar and built by a consortium led by Boeing Vertol, the Morgantown PRT was derided at the time as a taxpayer funded boondoggle costing 3–4 times the original estimate. However it eventually proved its worth as a reliable, low cost automated transit solution.

Opening in 1975, the network had just three stops to start with. It was expanded in 1978 to five stations, still the full extent of the network today. Two maintenance depots service the 70 vehicles in current use.

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While for most of its operational life it boasted a 98% uptime, eventually things began wearing out and the Morgantown PRT reputation started to sour. So it underwent an extensive reburbishing in 2012 which replaced all the vehicles, central control system and other infrastructure.

Morgantown PRT may have served as something of a cautionary tale to other schools and small towns considering PRT at the time. It resurfaces as a concept and potential urban transit solution every few years but typically gets passed over in favor of light rail, more lanes, or expanded bike paths.

Economies of scale is partly to blame. Light rail is commonplace around the world. There are lots of manufacturers making trains. There exist almost no companies making PRT pods and their support systems. One of the rare exceptions is UltraPRT, which makes the pods used in Heathrow Airport, and Masdar City:

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Opened in May of 2011, the Heathrow PRT system shuttles customers 2.4 miles between the business parking lot and Terminal 5. The next airport to get an UltraPRT system will reportedly be Chengdu Tianfu International Airport, as announced in 2018.

It’s planned to be considerably more extensive than Heathrow’s, with 6 miles of guideway, 4 stations and 22 pods, connecting airport parking to two terminal buildings. Masdar City is another example of a PRT project the developers went all in on.

Masdar City is an ecological design showpiece for the United Arab Emirates, located in Abu Dhabi. It’s powered purely by renewables, grows much of its own food and cars aren’t permitted. You guessed it, like the Epcot that never got built, Masdar City relies entirely on PRT for public transit.

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Subterranean PRT at that. Which to me seems like a subway with extra steps, but I digress. The UAE government has so far been impressed with the system’s performance, signing another contract with Ultra in 2017 for a PRT network to be built in Ajman City.

A proposed PRT system is also in the works for Gurgaon, India and the Heathrow network is planned to be expanded when the budget permits to include Terminals 2 and 3, as well as connecting to nearby hotels with over 400 pods.

Clearly PRT can work in certain niches where a train is too much, but the distances are unreasonable to traverse every day on foot. But nor are they the one size fits all wonder solution to the world’s public transit woes that was envisioned in the 60s and 70s.

PRT was devised in part as an answer to the problem of how to make driverless cars before computers and software were up to the task. Nowadays that’s no longer an issue, and PRT is a solution without a problem. The low speed driverless pods now seen around Shenzhen and Denmark bear more than a passing resemblance to PRT however:

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This compromise leverages most of the advantages of PRT, but falls down in that it doesn’t separate the pods from pedestrian or automotive traffic (depending whether the system in question uses streets or paved bike paths). Part of the promise of PRT was the elevated guideways, moving light traffic up off the streets and sidewalks into its own transportation channel which would theoretically reduce both sidewalk and road congestion.

Had we moved ahead full steam with PRT when it was in vogue, those elevated rail or guideway networks would’ve been built and would still exist for PRT to use today. But we dragged our feet on that aspect of it, perhaps for the best judging by the ultimate cost of the Morgantown PRT network.

Is PRT doomed to forever be a niche solution, only seen at airports, theme parks and college campuses? Does the steady improvement of driverless electric cars threaten PRT’s raison d’être? Or will the growing transportation needs of urban centers, along with the drive to reduce road congestion, finally give PRT its day in the sun?

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That remains to be seen. I for one hope they find wider adoption as a more comfortable and dignified alternative to light rail in cities. One which doesn’t require passengers to spend their journey immersed in the BO of a hundred strangers, or packed in like sardines during their morning and evening commutes.

If we had it to do over again in Portland, I’d prefer a suspended PRT rail network in place of the streetcars we got instead. Having to contend with light rail sharing road space with cars could’ve been avoided. I can also scarcely think of a more pleasant way to tour the city, back before it turned into what it is now anyway.

What do you think of PRT? If you live in a city, can you envision it working well for your commute? Do you frequent an airport where it would make a more convenient solution to getting from the parking lot to the terminal than shuttle buses? Do you foresee PRT enjoying expanded use in the coming years? An idea whose time is yet to come, or one best left in the history books?