Weighting Different Types of Time
It has been observed that travellers prefer time spent on some parts of their journey over time spent on others. A typical journey can be divided into four parts:
- Walk from the origin
- Wait for the vehicle
- Ride in the vehicle
- Walk to the destination
(All of these apply to public transport journeys; the wait for the vehicle does not generally apply to car or bicycle journeys, and for walk-only journeys, there is no division into parts.)
Typically, although travellers "dislike" all time spent travelling, they dislike walking and waiting parts of the journey more than in-vehicle journey time, and thus would be willing to pay more to avoid them. This results in a higher value of time for those parts of the journey than the main in-vehicle part of the journey. The function u(w) mentioned earlier can therefore be considered to consist of differing sets of valued time.
An alternative approach to applying different values of time to each part of the journey is to apply a weighting to time spent on each different part of the journey which quantifies the level of dislike a traveller has for time spent on that bit of the journey relative to time spent in-vehicle. For example, if a traveller considers 12 minutes' walk to be "as bad" as 10 minutes in a vehicle, then each minute of walking time is equivalent to 1.2 minutes of in-vehicle time. In this manner, all parts of the journey can be converted into their equivalent in-vehicle time.
Once the equivalent in-vehicle time for the whole journey is calculated, this can be converted to a monetary value as described earlier.
Read more about this topic: Generalised Cost
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