As small time savings and losses comprise a large proportion of the effects in many projects, this would make the ERR dependent on the size of the project and would discourage sensible examination of projects on an incremental basis. However, these results may be an artifact of the research procedure as it is more difficult for respondents in SP experiments to imagine adjustment of activity patterns which would allow a small time saving to be put to beneficial use by activity rescheduling, than to see the immediate problems caused by a time loss on an existing tightly scheduled activity pattern. Given also the practical difficulty of using any different convention it is recommended that the same unit values be attributed to time differences irrespective of the size or sign of the difference. Walking and waiting time Walk, wait and transfer times have usually been assigned higher values both in forecasting and evaluation applications. The recent European studies still show transfer times and waiting times with values between one and a third and two times those of in-vehicle times.
Chilean studies show an even higher ratio.
Waiting in inclement conditions in Sweden predictably had a particularly high value. Although the most recent UK study did not show any difference between walking and in-vehicle time savings for commuters this was for car travellers for whom walking times were generally low. The value of non-working time is, in economic terms, a ratio of the marginal utility of time to the marginal utility of money, and hence is dependent on changes in income, changes in the opportunities for spending that income, changes in the amount of time disposable for leisure and changes in available leisure opportunities. A priori theorizing has yielded no conclusion on size or sign of the net effect on the value of time. Recent studies in the UK and The Netherlands suggest elasticities of VoT with respect to income of approximately 0.5.