In message , at 12:13:37 on Tue,
10 Jul 2018, Mike Bristow remarked:
In article ,
Roland Perry wrote:
In message , at 11:15:01 on Tue,
10 Jul 2018, Mike Bristow remarked:
You think that trips made outside the peak are going to be *slower*?

First, sort out in your head the difference between statistical average
speeds, and the average speed for one specific trip.

This subthread started out with you disbelieving the TfL supplied
figures (in , John Williamson quoted
them; in you rubbished them).

"Finding something hard to believe" is a very gentle form of
'rubbishing'.

After some to-and-froing over the basis of your disbelief I gave
an example journey that more-or-less matched the figures of TfL.

Indeed.

At which point you suggest I misunderstand averages.

And you do (misunderstand). Average speed figures are calculated from
thousands of journeys on different roads with different degrees of
congestion (and at different times of day).

The fact you made one journey which 'matched' is simply co-incidence.

I could just as easily have spoken of a trip I did in perhaps 2015 from
Aldwych to Marylebone, about 3.5miles in 45 minutes, and claim that the
8mph figure is therefore wrong.

That was on an unremarkable weekday lunchtime, but anecdata can also be
affected by special events - my most likely reason to be driving in
London these days is traversing Watford and Uxbridge to get to Heathrow
airport because the M25 is closed. I don't expect that to correlate with
any of the published data.

But it can look pretty on a map:

https://scontent-lhr3-1.xx.fbcdn.net...15447893752163
7_7216041464188430701_n.jpg?_nc_cat=0&oh=a39052329 a8fcf074041113eaa72770
c&oe=5BDD14A9

You seem to prefer your own theories over the measurements carefully
made by experts

I was questioning the continued validity of the measurements given the
roll-out of 20mph zones, which are of course a top limit before delays
caused by "weight of traffic", traffic lights, vehicles double parked,
and even road works.

I'd be happier if it was known what radius from the centre TfL's 7.8mph
represented, and thus where 17.4mph kicks in. This 2017 study as London
at 5.13mph (up to 1 mile) and 8.34mph (up to 5 miles):

https://www.aph.com/community/holida...lower-average-
speeds-uks-major-cities-revealed-2017/

Also whether the 8.34mph is for all the traffic within 5 miles, or just
that between 1 and 5 miles. Ditto for the TfL data.
--
Roland Perry