Generalised cost
In transport economics, the generalized cost is the sum of the monetary and non-monetary costs of a journey.
Monetary (or "out-of-pocket") costs might include a fare on a public transport journey, or the costs of fuel, wear and tear and any parking charge, toll or congestion charge on a car journey.
Non-monetary costs refer to the time spent undertaking the journey. Time is converted to a money value using a value of time figure, which usually varies according to the traveller's income and the purpose of the trip.
The generalised cost is equivalent to the price of the good in supply and demand theory, and so demand for journeys can be related to the generalised cost of those journeys using the price elasticity of demand. Supply is equivalent to capacity (and, for roads, road quality) on the network
In a basic form, the generalised cost (g) is composed of the following:
In a congestible system, every traveller imposes a small delay on every other traveller, increasing the journey time for all travellers. The generalised cost function can be expanded to reflect this congestion delay.
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