[sustran] Re: [tmip] System dynamics in transport policy analysis

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From: Juan de Dios Ortuzar <jos at ing.puc.cl>
Subject: Re: [tmip] System dynamics in transport policy analysis
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Harun al-Rasyid,

Incorrect models or models incorrectly used have problems. I am convinced
that consistent equlibrium models (which are available in some places
nowadays) perform better than what you describe (for instance, building
more roads does not necessarily lead to less congestion, on the contrary,
as mode choice may change with the improvement, a new equilibrium is
reached where more people use cars and congestion may even end being
worse). The trouble is if you use inconsistent models (as most available in
practice) or if you do not have the ability or experience to interpret
correctly the model output (which is often not simple at all to judge).

One problem that current models do have though is that the sequence of
dcecisions does not matter (according to the model) while it certainly does
in practice. Think about implementing road pricing before or after
implementing substancial improvements to the public transport system.

Cheers,

J de D Ortuzar

A 06:04 PM 2/06/99 +0700, Harun al-Rasyid Sorah Lubis escribi=F3:
>From: "Harun al-Rasyid Sorah Lubis" <halubis at trans.si.itb.ac.id>
>
>Most  applied model in transport are non-structural and lack of feedback
>mechanisms.
... quoted stuff deleted .....


Juan de Dios Ortuzar        e-mail: jos at ing.puc.cl
Departamento de Ingenieria de Transporte
Pontificia Universidad Catolica de Chile
Casilla 306, Cod. 105, Santiago 22, Chile
Tel: 56-2-686 4822  Fax: 56-2-553 0281