Thanks to those who responded to my poll (below). Interesting responses
received so far, but more would help to enlarge the sample.
Respondents to date made little (if any) distinction between the predictive
accuracy expected for tolled versus toll-free roads. So we can perhaps
collapse the questions (making it even easier/quicker to complete).
All I need is seven numbers (percentages). Simple replace the question
marks below. What level of forecasting accuracy would you regard as being
reasonable for:
Existing ('brownfield') Projects:
Next day = +/- ?%
1 Year = +/- ?%
5 Years = +/- ?%
20 Years = +/- ?%
New ('greenfield') Projects:
1 Year = +/- ?%
5 Years = +/- ?%
20 Years = +/- ?%
And simply post your reply back to me at [log in to unmask]
Thanks again,
Rob
www.robbain.com
-----Original Message-----
From: Universities Transport Study Group [mailto:[log in to unmask]] On
Behalf Of Robert Bain
Sent: 22 March 2011 15:08
To: [log in to unmask]
Subject: [UTSG] What is reasonable?
*** APOLOGIES FOR CROSS-POSTING ***
Hi
I've published on traffic forecasting accuracy in the past, and I'm
currently researching for a new, updated piece.
Most studies of predictive accuracy have compared point-forecasts with
outturn figures. This is a very harsh (unreasonable?) test. Perhaps we
should establish what is 'reasonable' in terms of forecasting capability?
This is a line of enquiry that I'm exploring.
I have a little spreadsheet (which is very quick to complete) in which I
present two scenarios: one for an existing ('brownfield') road and the other
for a new ('greenfield') road. What level of accuracy do you think is
reasonable for, say, a one-year traffic forecast? Or a five-year one?
The UTSG list will not accept attachments so contact me directly on
[log in to unmask] and I'll send you the spreadsheet. You simply insert your
responses in the appropriate yellow boxes. Eg. +/- 10%, or +/- 50%. It's
very quick and I'd really appreciate your views.
I've given two options in the spreadsheet. One for a toll road (in green)
and the other for a non-tolled ('regular') road (in blue). You may - or may
not - feel that tolling per se changes the level of accuracy which
might/should be expected.
I'll compile my results and will share them with List Subscribers when
complete.
If anyone knows of any similar research, related guidelines etc., please
draw them to my attention.
Many thanks,
Rob Bain
Visiting Research Fellow, University of Leeds
www.robbain.com
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