[sustran] Re: Road building

[Harun al-Rasyid Sorah Lubis]

That is what the transport planner called : suppressed demand.

Just like a water in a resorvoir, temporarily kept. Once you open the valve,
it leaks to any spare channel (read capacity) added.

In routine consultancy work, i.e. four step transport modeling, they tackle
this through, over-assignment technique, either assuming elasticity on the
demand curve or doing an adhoc technique called matrix capping. I guest in
Canada they do the latter, while in the  UK they use the former. UK  has
formally introduced this in the transport planning practice.

Harun
ITB/Bandung
-----Original Message-----
From: Roger Higman <rogerh at foe.co.uk>
To: sustran-discuss at jca.ax.apc.org <sustran-discuss at jca.ax.apc.org>
Date: Sunday, July 30, 2000 11:39 PM
Subject: [sustran] Re: Road building


>
>> I am urgently looking for material that will establish the
>> point that additional road building does not really help in
>> the long run since the additional traffic that it generates
>> soon clogs the new roads as well as the old one.
>
>The classic UK reference is:
>
>Standing Advisory Committee on Trunk Road Assessment "Trunk Roads and the
Generation of Traffic" December 1994 (London: HMSO)
>
>This found that: "the economic value of a scheme can be overestimated by
the omission of even a small amount of induced traffic".
>
>It said induced traffic is "of greatest importance in the following
circumstances:
>
>- where the network is operating or is expected to operate close to
capacity;
>- where traveller responsiveness to changes in travel times or costs is
high, as may occur where trips are suppressed by congestion and then
released when the network is
>improved;
>- where the implementation of a scheme causes large changes in travel
costs."
>
>Roger Higman
>Senior Campaigner (Climate and Transport)
>Friends of the Earth (E,W+NI),
>26-28 Underwood Street,
>London, N1 7JQ
>
>Tel     + 44 171 566 1661                       Fax   + 44 171 490 0881
>Pager     07654 663772
>E-mail  rogerh at foe.co.uk                        http://www.foe.co.uk
>