Wednesday, May 25, 2005

Why public transport can't work

Politicians and environmental campaigners would like everyone to make less use of their cars and to use public transport instead. Their sentiments are admirable but there is one enormous problem... None of the existing public transport systems can ever replace the automobile... "Oh but you're wrong!" I hear you cry. No, I'm not and I'll explain why.

The automobile and all of the existing public transport systems (including trains, trams, monorails, buses etc) are fundamentally different transport concepts.

The automobile is an individual transport technology, that is, it is designed to transport an individual from A to B. All of the existing public transport systems are group transport technologies, that is, they are designed to transport groups of people from A to B.

This may not sound like a big distinction but the consequences of this difference are huge;

A group transport vehicle must stop regularly at stations in order to allow passengers on and off, it cannot be avoided. If you reduce the number of stops then you also reduce a passengers access to transport and fewer people can use it. The consequence of frequent stops is that the average speed of the system is extremely poor indeed as the vehicle spends much of it's time accelerating, decelerating and stopped. The only way to improve the average speed and reduce the journey time is to prevent stops, having a vehicle which has a high top speed doesn't matter because each time it stops the time taken for the journey increases and the performance suffers.

A group transport vehicle cannot take you directly to where you want to go. By it's very nature the group vehicle can only take you approximately in the general direction you want to go. They have to provide an average destination approximately where most people would like to travel. The group transport vehicle must always follow a fixed route. This means that passengers always have to make additional journeys, they must travel to the station or stop and once they reach the route destination they again have to travel to their final destination by other means. Each additional change of route or vehicle imposes additional delays on the passenger and the performance suffers.

A group transport vehicle cannot be used on demand. Because passengers all wish to travel at slightly different times, the group vehicle must be run to a schedule. The number of vehicles on the schedule obviously depends on the probable occupancy, if few people wish to use it then scheduled vehicles will be few and far between meaning that passengers have to wait often for long periods until the next vehicle arrives. This also reduces the performance. If a route is popular then the schedule will be frequent and the wait will be less, but will still be there and the passengers may be required to stand, or even crush on to the vehicles.

A group vehicle must by it's nature be large and therefore heavy in order to carry large numbers of passengers. This size and weight impinges on the underlying infrastructure. In order to support a large and heavy vehicle, the underlying road or rail must be heavily engineered, this means that the vehicles themselves and the infrastructure to support them must be expensive and less than environmentally friendly. Indeed accelerating and decelerating a very large and very heavy vehicle comsumes a lot of energy, far more than a small vehicle meaning that group vehicles are only environmentally friendly when they have many occupants, such as during the rush hours. At off peak times when they are almost empty they are very enviromentally unfriendly indeed.

These are fundamental failings of conventional public transport systems which cannot be overcome by any group transport vehicle. They are inherent in the system.

Cars obviously have their own problems with inefficiency, congestion, cost but they can never be replaced by group public transport systems because they are a fundamentally different concept... They are an individual transport technology.

I put it to you that spending billions of pounds and effort lobbying to replace the car with conventional public transport systems is a futile exercise, the overwhelming majority of journeys will continue to be made using the car until there is a credible alternative which can replace most of the features the car has; On demand 24 hours per day, fast door to door service without the need to know routes or worry about schedules. And this can never be accomplished by conventional public transport.

The solution to replacing the car is to develop a public transport system which makes use of individual vehicles, and not group vehicles. Fortunately, transport researchers have been developing exactly this kind of mass transit system over the last 40 years. It is called Personal Rapid Transit (PRT).

There are a couple of companies started by transport researchers trying to produce working PRT systems. The largest American company is Taxi 2000, their system is called Skyweb Express. The most developed UK PRT system is called ULTra, developed from a University of Bristol spinoff company called Advanced Transport Systems Ltd.
Only one of these systems, or other PRT implementation very much like them can make a significant dent in car usage. Trains, buses, monorails, trams simply cannot make a useful contribution.


At Sunday, May 29, 2005, Blogger Ned Luddington said...

PRT is totally bogus.

Taxi 2000 is suing its founder and former CEO in Court in Minneapolis.

ULTra is unlikely to replace trams or automobiles... Ultra runs on batteries.

PRT Skeptic Site:

At Sunday, May 29, 2005, Blogger Mr. Precision said...

I notice you haven't come up with any technical reasons for your assertion. "totally bogus" just doesn't cut it where I come from as a valid argument and yes, I've seen roadkillbill's site.

Sure, the ULTra system is unlikely to be a large city wide scale system. It's being considered for smaller scale applications, like Heathrow Airport.

The Skywebexpress system though is being engineered to be able to handle large scale high performance city wide implementations. With linear motors, remarkably few moving parts, short inter vehicle intervals etc. The fact that there are political problems within the company does not change the fact that group based vehicles like trams can never take a significant number of automobiles off the roads. PRT is it.

All train/tram/monorail schemes have blatently failed to deal with the road congestion problem. It's a feature of their design.

At Monday, May 30, 2005, Blogger Ned Luddington said...

The fact that there are political problems within the company does not change the fact that group based vehicles like trams can never take a significant number of automobiles off the roads.

According to a recent new story, Taxi 2000 isn't having "political problems". Taxi 2000 is suing it's founder and former CEO... that's pretty serious.

Most transit advocates don't promise that that rail transit will solve congestion. Transit gives people who don't want to drive or take a bus or a train a choice.

Here in Minneapolis, the Hiawatha LRT is a huge success. People choose to ride the LRT of all kinds of reasons. It's fast, safe, a lot of fun to ride and a lot less expensive than driving and parking a car.

Now that LRT is a huge success, the PRTers are looking like a bunch of crabby people who don't want us to have the same choice of transportation most modern cities have.

PRT aint going to happen any time soon... even the PRTers agree on that.

At Monday, May 30, 2005, Blogger Ned Luddington said...

Transit gives people who don't want to drive or take a bus or a train a choice.

Meant to say transit gives people who don't want to drive and prefer to take a bus or train a choice.

At Monday, May 30, 2005, Blogger Mr. Precision said...

According to a recent new story, Taxi 2000 isn't having "political problems". Taxi 2000 is suing it's founder and former CEO... that's pretty serious.

In America people sue over hot coffee. It sounds like politics to me.

Most transit advocates don't promise that that rail transit will solve congestion. Transit gives people who don't want to drive or take a bus or a train a choice.

Here in the UK they have been promising that congestion can be reduced with the introduction of more trains and trams. Unfortunately the effect has been close to zero, largely because of the features I mentioned in the article.

I know that in the US, tram and train development is minimal but that isn't the case in the UK we have a large and extensive rail network. Despite that, around 90% of journeys are still made by car. The statistic is largely repeated across Europe where they spend even more of their tax revenue on public transport and it comes down to the fundamental nature of the beast:

If you increase access to transit by adding stations, you hurt the performance badly and if you restrict access you improve train performance but lose customers because overall performance falls.

Looking at the Hiawatha LRT system, they appear to have chosen the latter option, relatively distant stations, will give a decent average speed but it means that customers will have to spend a lot of time walking to and from the stations.

They claim 2 mins between stations and an average speed of 40mph, 1.3 miles between stations that's on average 2/3 of a mile walk even if you lived by the line, more if you don't, 13 minutes then you have another 13 mins or so to get to your destination when you get off. So your 2 minute or 4 minute journey between a couple of stations turns into a 28 minute or 30 minute overall journey and I'm not even adding on schedule waits and stops. The car, same journey 5 mins door to door at 30mph. It really isn't surprising that a relatively few 10% or so of people will use the train. "Huge success"? Maybe if you have very low expectations for the money you've invested.

Of course if the train doesn't go where you want to it's no use at all.

I also agree that PRT isn't going to happen soon, transport infrastructure always takes a long time, PRT is at the stage that rail was when Stevenson built the Rocket, being considered for a few specific industrial applications.

At Tuesday, May 31, 2005, Blogger Ned Luddington said...

That "give the inventor chap a break" argument is so old. Invent it with your own money and stop asking to raid the public purse. We got more important things to spend scarce public dollars on than silly pie-in the-sky schmes like PRT.

Check out this blog:

PRT is a Pathetic Waste of Time.

At Tuesday, May 31, 2005, Blogger Mr. Precision said...

That "give the inventor chap a break" argument is so old. Invent it with your own money and stop asking to raid the public purse.

What are you talking about? All of the PRT systems developed so far have been privately financed and are trying to compete on their merits. I think I should point out that the train systems you are so proud of are on the other hand heavily subsidised. They are so undesirable that they simply couldn't exist without subsidy. Your "successful" Hiawatha line gets 8 million dollars per year from the council (50% of it's budget) because it can't be run without it.

No PRT system anywhere has been granted anything like that kind of money and this is expenditure on a yearly basis, not even a one off research and development grant.

In the UK, our extensive rail system is subsidised to the tune of around 3.8 billion pounds per year, yes, that is the equivalent of six thousand eight hundred and forty millon dollars PER YEAR. It is subsidised because rail doesn't, can't work.

We got more important things to spend scarce public dollars on than silly pie-in the-sky schmes like PRT.

Go and get your facts right before you dare talk to me about "scarce public dollars", "pie-in-the-sky" and rail in the same breath.

At Tuesday, June 07, 2005, Blogger AaronP said...

That's enough.

Let's all stop bashing each other's favorite form of
transportation. It's an apples and oranges arguement, and it doesn't get anyone anywhere. That very, very old debate just demonstrates how people aren't really good at anything but blathering at each other without getting anywhere. Surely, we can do much better.

I am a big fan of PRT. I can't help talking about it
everywhere I go. But, you know what, it's not that "rail can't work". It's not even that it doesn't work
as well as PRT. It's that rail works differently than
PRT which works differently than cars, which work
differently than airplanes, boats, bicycles,

If you're for PRT, you should be FOR the technology in its own right, and for ways to use it intelligently.
Rather than try to beat out other options (useful or
not), we ought to play FOR its introduction and
development (and improvement), not AGAINST other
technology. That's a ridculous and losing way to
think about how technology serves civilization.

It's also old.

And boring.

Instead, let's all talk about ways to creatively use
technology smartly to improve our lives and
communities. In fact, what about the fact that PRT's
principles of low-impact and individual service lend
itself well to INTEGRATE with all other forms of
transit, SAVE on precious publlic and/or private
resources (natural or otherwise), and really BENEFIT
THE RIDER...who ends up with many options, rather than just one or the other.

You can't fix things with only one tool in your
toolbox, but you do have to pick the right tool for
which ever thing needs fixing. And a brain.

Enough. Really.


PS These opinions are my own, and do not necessarily reflect the position of Citizens for Personal Rapid Transit.

At Tuesday, June 07, 2005, Blogger Mr. Precision said...


I agree with your sentiment, hell I even agree rail has a place in an integrated transport system. However, I live in a country with a large integrated rail network, we've had it forever, to the point that it's part of the national consciousness but it cannot solve the problems that the politicians and the environmentalists want it to solve. We're literally throwing 3.8 billion pounds(GBP) per year at the system to try to get it to solve those problems with even higher subsidies on the way, and it just isn't working. To give an example of the size of the UK rail system, if it was scaled from the UK's ~50 million people to the US ~250 million people, the US government would be subsidising it to around 35 billion dollars per year and that only covering a fraction of the running costs.

Yes, you're right, it is old and it is boring. I would love to simply point out the advantages of PRT, and I do where I can, but unfortunately positive campaigning is far less successful than negative campaigning, ask any politician or any environmentalist for that matter. This means that it isn't enough just to sing the praises, we also have to point out to the politicians, environmentalists, everyone that they are trying to hammer a square peg into a round hole. The systems they keep buying simply do not function the way they think they do, can't function the way they wish they could.

Sorry, and regards.

At Tuesday, June 21, 2005, Blogger David Maymudes said...

As you express an interest in PRT, you might be interested in a new video animation of what PRT would look like if implemented as a corporate campus shuttle. The setting is Microsoft HQ in Redmond. The video and related information are on a URL set up by the Seattle PRT group at

At Monday, July 04, 2005, Blogger ben said...

With a bit of thinking public transportation can be made much better. Delays due to frequent stops can be offset by tying the bus into the traffic light system so that they never get red lights (I've heard this is done in Ottawa, Canada).

A bus weighs about 17500kg, 30 people driving a smart car would be 30*790kg=23700kg, so almost the same if everybody were to drive a smart car...which they're not, so I'm not too convinced that a bus would do that much more damage than 30 smart cars.

I'm surprised that the PRT is so cheap. I doubt that any government would want to give up the investment that they've made in roads though. Maybe PRT is the answer. Is each individual vehicle some type of plug-in electric vehicle until it reaches the rail? Another similar concept is to take a bike with you on a bus. The city busses where I'm from all have bike racks so that you can bring your bike with you while on the bus.

Keeping cars on the road is definitely not the answer though for many reasons. Cars in the US use 26% of all the energy that the US uses (oil makes up 40% of energy used in the US, cars use 2/3rds of that oil), and US cars use 16% of the worlds oil...and China will soon have even more cars than the US. Then there's the pollution problem, in Canada health cost of air pollution is higher than that of road accidents (not too sure how much of that air pollution comes from cars, but it must be a significant amount). Where I live there's now a smog warning "until further notice".

As long as you live in the city then there should be no reason to own a car because public transportation actually does work in the city. At least where I am.

At Wednesday, October 05, 2005, Blogger Livenwealthy said...

This comment has been removed by a blog administrator.

At Friday, October 07, 2005, Blogger Dennery said...

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