In an age of concern about climate change it is important to understand the induced traffic to be expected following the building or extension of a road. A review of international literature was undertaken on induced demand, along with an examination of the very limited evidence available in New Zealand. A search was also made for an induced demand tool suitable for use within the early stages of business case development – that is, before more extensive projects are defined and transport modelling sought. The few tools available did not incorporate the contextual information that the international research revealed as important, so a tool was developed by the project team. Important findings included that key determinants of induced travel are the travel cost reduction achieved by new lanes and the base road network used to infer VKT growth. The tool combines a lane-km elasticity with a cost elasticity approach to guide the user through the logic and calculations to indicate a potential range of induced VKT to expect from the proposed additional road lanes. Rules were applied to indicate the scale of land use effects on VKT.
BYETT, A., J.J. LAIRD, J. FALCONER and P. ROBERTS (2023) BYETT, A., J.J. LAIRD, P. ROBERTS and J. FALCONER (2021) Induced Traffic Assessing induced road traffic demand in New Zealand. Waka Kotahi (NZ Transport Agency) Research Report RR XXX (to be published)