The Q-analysis of road traffic systems

Johnson, J. H. (1981). The Q-analysis of road traffic systems. Environment and Planning B. Planning and Design, 8(2) pp. 141–189.


Traditional methods of describing the road transport system are criticised because they fail when used by planners and engineers. It is argued that a fundamental reason for this lies in road traffic theory being self-contradictory: the dynamic microtheory describing shock-wave behaviour in traffic queues is incompatible with the static macrotheory based on equilibrium principles. Q-analysis can be applied consistently both at the microlevel and at the macrolevel, which are related by algebraic hierarchies. This clarifies the need to make the macrotheory dynamic and begins so by using the recently extended notion of q-transmission. The theory is illustrated at the microlevel with a study of road intersections, and at the macrolevel with a study of a town and a hypothetical property development. A section introducing hierarchical routes shows how the microlevel and macrolevel may be combined in the more general context of land use. In this way it is possible to construct an integrated description of the land-use-activity-transportation system.

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