2 Understanding travel demand and travel behaviour
Given an initial endowment and income, people are expected to make rational economic decisions after evaluating the costs of the different options they have to meet a particular need, e.g. weekly commuting travel. Their actual travel behaviour will not only reflect this personal economic evaluation but also their preferences.
2.1 Traveldemand
Travel demand refers to the amount and type of mobil- ity that people would choose in a particular situation.
This reflects their ability and willingness to pay (see Box 3), and therefore the value they attach to specific travel activity, such as a particular trip or mode. This value can be highly variable: some trips (such as commuting and visits to healthcare services) are important so people take them even if their price is high, but others (such as impulse shopping and some recreational trips) are lower value and so people will only take them if they are cheap. This is illustrated in Graph 1. As a result, the number of trips people take tends to increase as travel costs decline, making lower-value trips seem cost effective.