The relationship between motorised private and public transport networks in Australian cities
In 1987, UK transport planner Martin Mogridge hypothesized that the average speed of road traffic in cities is set by the average speed of alternate parallel public transport networks. Mogridge reasoned that because public transport networks operate to fixed-schedules, or timetables, the marginal cost of trips is also fixed. By contrast, road networks operate to variable speeds because drivers determine their own departure times and speeds can vary given the number of drivers on the network causing congestion. If the marginal cost of travel on the road network increases beyond that of the public transport network, then some individuals will shift from the road network to the public transport network in order to reduce their travel costs, thereby establishing an equilibrium between the two networks.
Mogridge explained this relationship using micro-economic theory, expanding the basic ideas used to account for why motorists shift between alternate road routes in their bid to reduce the marginal cost of their trips until no further time advantages can be achieved.
The Mogridge Conjecture has significant implications for sustainability because it identifies the mechanism by which average road speeds are determined and in the process highlights the key role played by public transport, which is seen as more sustainable than a high reliance on private road transport. Average road speeds are the key performance indicator used by road agencies to gauge their performance. The Mogridge Conjecture highlights the need for road agencies to collaborate with public transport service providers in order to achieve their key service obligations.
ISF invites potential candidates interested in extending our knowledge of the many issues that arise out of the Mogridge Conjecture, suggesting several areas in which a contribution to knowledge could be made.
Research could empirically test the Mogridge conjecture by investigating the relationship between parallel road and public transport speeds in Australian cities under different conditions. Research could examine the use of key performance indicators by government agencies - like average road speeds - and how transport theory like the Mogridge Conjecture is used to inform decision-making. Research could investigate the degree to which professional practitioners and government agencies are aware of the relationship embodied in the Mogridge Conjecture and how it might be used by agencies to better achieve their core business.
For further information about this topic contact Dr Michelle Zeibots
References
Mogridge, M.J.H. 1990, 'The relationship between congestion on the roads and public transport', in Transportation Planning Systems, Vol. 1, No. 1, pp. 11-19.
Mogridge, M.J.H. 1990, Travel in towns: jam yesterday, jam today and jam tomorrow?, MacMillan Reference Books, London.
Mogridge, M.J.H. 1997, 'The self-defeating nature of urban road capacity policy: a review of theories, disputes and available evidence', in Transportation Policy, Vol. 4, No. 1, pp. 5-23.
Mogridge, M.J.H. & Holden, D.J. 1987, 'A panacea for road congestion? A riposte', in Traffic Engineering and Control, Vol. 28, January Issue, pp. 13-19.
Mogridge, M.J.H., Holden, D.J., Bird, J. & Terzis, G.C. 1987, 'The Downs-Thomson Paradox and the transportation planning process', in International Journal of Transport Economics, Vol. 14, pp. 283-311.
