In this paper, four frequently cited approaches to future studies are criti
cised. We use examples mainly from the field of transport research. The fir
st approach is the tendency to try to establish cyclic behaviour in socio-t
echnical changes. The second is the view that transport and communication a
re positively correlated. The third is the so-called 'hypothesis of constan
t travel time', according to which, the average daily travel time of a popu
lation is more or less stable. The fourth is the alleged causal relationshi
p between urban density and petrol use.
The use of these approaches is criticised for a number of reasons, among ot
hers for over-simplifying the underlying mechanisms and for being too deter
ministic. In cases where drastic change is needed, current trends must be b
roken, but perhaps through measures other than those indicated by the above
approaches. In other words, the cited approaches may overlook interesting
opportunities and fail to urge necessary action.
Backcasting is put forward as a more promising approach, especially for sit
uations where great change is needed, However, it has been found in this st
udy that backcasting and different forecasting approaches an complementary.
The argument is that backcasting is mainly appropriate where current trend
s art: leading towards an unfavourable state. Therefore, forecasting method
s are necessary because they inform the backcaster when backcasting is requ
ired.
Finally, the paper discusses the use of different models in planning, prima
rily in the context of their role in the path analyses of backcasting scena
rios. (C) 2000 Elsevier Science Ltd. All rights reserved.