In message
-sept
ember.org, at 09:47:58 on Mon, 2 May 2016, Recliner
remarked:

And was it based on 1985 service levels and fares, or today's?

Fares were adjusted for inflation, but used current passenger numbers.
Back when the line was built all the passengers were going to T123,
whereas with today's figures only about half of them are. Putting some
numbers on it, Heathrow was handling 30m passengers when T4 was being
built, and latest figures (2015) have T123 handling 32.6m [T4+T5 is
40.8m].

So you need to reduce the volumes by about 10%, for the average in the
1977-1986 period?

I wasn't going to bother estimating second order quantities. For
example, I've ignored the passengers abstracted from the Piccadilly Line
by HEx.

Very few, I suspect. Not many potential Tube pax would be prepared to pay
HEx fares.

HEx is there to abstract from the taxi trade, but there are still people
who would pay HEx fare who previously wouldn't have paid taxi fares and
thus would have used the tube.

Also, I wonder how much of that traffic was simply displaced from Hounslow
West, which previously provided the less-satisfactory Heathrow link?

That's accounted for by me using the very low figure of £2 extra fares
(at today's prices) being put in the kitty. The rest of the fare goes
towards funding Hounslow to Central London.

You really need to compare fares and traffic in the 1977-1986 period with
the 1977 investment.

All monies have been adjusted for inflation, and I'm not sure that T123
tube station is now that much busier than in the early 80's for the
reasons I've given. Heathrow has always had a relatively high percentage
of passengers using public transport - 34% in 1995 is one figure I've
managed to find. And that report mentions 12 million passenger and 3
million staff using the Piccadilly Line. Compared to shade under 10m
for T123+T4 today.
--
Roland Perry