Fact-Checking the "PRT Boondoggle" Blog
A project of the PRT NewsCenter

Tuesday, August 30, 2011

Statistics For Luddites

Mock Journalist, Part XII

What does Ken Avidor do when a PRT system is getting lots of positive media exposure? You wait for the imprecision that inevitably creeps in when downstream news outlets pick up the story.

So it was with the New York Times story about the new podcar system at Heathrow Terminal 5. Jim Witkin's August 5 post in the paper of record's Wheels blog has been picked up by dozens of general news websites and environmental, energy and design blogs. It has also spawned hundreds, if not thousands, of tweets.

Of course this means Avidor needs something he thinks could blunt* this publicity. It came courtesy of the August 12 Airport International News.

NY Times 'Wheels' blog
August 5, 2011
Airport International News
August 12, 2011

Pod Cars, Moving Silently at Heathrow's Terminal 5


LONDON — Travelers passing through Heathrow Airport have an opportunity to experience the not-so-distant future of airport transportation systems in Terminal 5, where a curious row of pod cars connects the terminal’s two business parking lots.

Since Wheels featured this personal rapid transit system in September, BAA, the company that operates Heathrow, and ULTra PRT, the manufacturer of the pod cars, have completed operational testing. Passenger service began in April.

Starting from the second level in Terminal 5, I recently took the pods for a chaperoned test drive — or more accurately, they took me. The electric cars have no visible accelerator or steering wheel; rather, they are completely automated and travel along a dedicated guideway. My only input consisted of a button push, which indicated my destination.

Quiet and comfortable were my first impressions of the five-minute ride between the terminal and parking lot. Onboard, the only sound over the familiar whirr of the electric motor was the recorded voice announcement from the iPad-like control panel inside the car, assuring me that I was “almost there.”

Several pod cars making the trip in the opposite direction whizzed past. Top speed is about 25 miles per hour. Alicia Griffiths, the BAA spokeswoman who rode along with me, assured me that the system had not experienced any accidents.

From an operational perspective, BAA is declaring the system a success, according to Ms. Griffiths. Two diesel-powered buses that used to make 216 trips daily along this route were removed from service in June, and now 22 pod cars [sic] shuttle nearly 800 passengers every weekday over 2.4 miles of track. Each car can carry four passengers and luggage. The cars have had very little down time for maintenance or repair; reliability has been above 95 percent, Ms. Griffiths said.

Energy efficiency is improved not only by replacing diesel vehicles with electric ones, but also because the pods move only on demand. Rather than making constant, endless loops between the terminal and parking lots, irrespective of passenger load, the pods operate only when travelers request them.

Passenger feedback also has been positive, Ms. Griffiths said, with many satisfied passengers using Twitter and YouTube to document their experiences.

Sharing one’s pod is optional, but I managed to climb aboard with one nattily dressed business traveler who, while acknowledging the technology’s gee-whiz factor, expressed his reservations.

“It seems to operate fine, but I wonder if this is just for PR value,” he said. “Would it work at the other, busier parking lots carrying many more passengers?”

BAA is betting it would. It has taken a financial stake in ULTra, convinced that these systems would have applications outside the airport in places like office campuses and dense residential and commercial developments. Both companies plan to continue promoting the technology to customers in Europe, North America and India, according to Ms. Griffiths.

Heathrow's ULTra PRT Robot Taxis Now In Service

Posted by Airport International's UK Correspondent

The ULTra PRT (Personal Rapid Transit) electric robot pods, previewed by Airport International back in August 2009, have now entered full operational service at the UK's flagship airport, London Heathrow.

Commissioned by Heathrow's operator, BAA, and developed by the ULTra PRT firm, the system's comprised of 3.86 kilometres of track and 22 individual pods.

The pods, which are entirely autonomous, link a pair of parking lots with the airport's newest passenger facility, Terminal 5, and they're available around the clock. That's not to say that they run 24/7, but that a passenger can ‘hail' one any time he/she likes.

In the absence of a constantly-running service, the system reportedly saves energy, compared to older transport methods. There are other environmental features, too, including the batteries that power them, which are recycled once they've been worn out.

Heathrow Robot Taxi

The frame of each Heathrow robot taxi is constructed from a plastic/steel mixture, making it fairly lightweight, while tubeless 13 inch tyres run between the underside of the pods and the track. The track itself is two-way, allowing multiple services to be run at one time.

Each pod is capable of accommodating four passengers plus their luggage and, at present, they're used by something like 800 passengers on a daily basis. The speed of these airport robot pods peaks at about 25 miles per hour and, since the fleet became operational, they've shown themselves to be pretty reliable, with a five per cent failure rate.

The Personal Rapid Transport concept is not unique to Heathrow Airport but nowhere else has it been implemented on the same kind of scale.

ULTra PRT Airport System

Research is now taking place into expanding use of the ULTra PRT airport system into other parts of the hub, potentially involving additional Heathrow terminals.

Airport International News did a good job of cribbing from Witkin-- or at least got the same information from BAA Media.

But when you paraphrase things, things get, well, paraphrased. Thus, the New York Times'--

"reliability has been above 95 percent"

--in Airport International News magically becomes:

"they've shown themselves to be pretty reliable, with a five per cent failure rate"

Amazing! A range of 95-99.999% has been transformed into a flat 95%, and eligible to be introduced into Ken Avidor's revolving door of talking points.

But let's go even deeper. When Avidor tweets the Five Percent Distortion and repeats it in his blog he's either showing his monumental ignorance of statistics, or counting on his readers being ignorant.

For even if a vehicle has a 5% unavailability rate, it doesn't mean there's a "1 in 20 chance" of missing your flight. For that to happen, all 22** of the Heathrow podcars would have to become unavailable at the same time.

Not 5%, but rather the chance of one unavailability times the chance of a second unavailability times the chance of a third unavailability, etc.

That is a probability of 0.05 ^22 = 0.0000000000000000000000000000238418579101563

* Ken's middle name is blunt
** There are really 21 pods, but the error doesn't affect the point of this exercise 

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