On constructing urban travel scales for analysing daily travel patterns : the case of the Greater Dublin Area, Ireland

Abstract

Over the last decade the Greater Dublin Area has witnessed significant land use and spatial restructuring. This has forced a distinct change in the spatial organisation of the built environment. Dublin has been transformed from an essentially monocentric city to a more dispersed polycentric city and this has created a new more complex geography of trip making. This research examines the impact of these changes on the journey distance and journey time efficiency of urban travel patterns. This is achieved through the construction of urban travel scales for analysing daily travel patterns. Each travel scale consists of four variables: the average minimum travel cost, the average actual travel cost, the average random travel cost and the average maximum travel cost. The transportation problem of linear programming was used to solve for a theoretical minimum and maximum average travel cost while the Hit-and-Run algorithm was used to simulate average random travel costs for the study area. The scales were constructed for the 2001 peak and off-peak; in order for a temporal analysis to be completed, they were constructed for the 1991 peak and off-peak periods also. Four evaluation measures were derived from the scales to assess the efficiency of trip making. The research found that there is a large difference between the amount of travel required by the minimum solution and the amount that occurs in reality. This implies that significant opportunities exist to reduce the average journey distance and average journey time if more individuals could be encouraged to travel to nearby destination opportunities. The results also found that car users have the potential to minimise journey distance to a greater extent when using the public transport network than public transport users themselves.