The demand for urban transport is complex, but the two most important considerations, usually, are time and money. The speed of transport and the cost of providing transport are closely related.

(a) Draw and explain an appropriate economic model(s) that illustrate(s) the trade-off between time and money in urban transportation and why it is so difficult to generalize the transportation options.

(b) Explain the considerations that can modify an individual's demand for urban transportation.