Estimation of Annual Traffic Volumes - A Model for Portugal

Abstract

The automobile characteristics in terms of the flexibility of practicable distances, comfort and time schedule autonomy have made it the most demanded mode of transportation. In face of the negative impacts associated with road transportation such as congestion, pollution and road accidents, the quantification of the regular and diversified use of the automobile has become a clear need of our society. The amount of travel in a road network, or in part of it, may be represented by the traffic volume (usually expressed in vehicle kilometres/miles of travel – VKM/VMT) which constitutes fundamental information about the use of a specific transportation system and for the analysis of its efficiency and particular impacts. This paper summarizes a study on methods for the estimation of annual traffic volumes at national level, developed by the National Laboratory of Civil Engineering (LNEC) and the Technical University of Lisbon (IST) in 2007. This study set up the context for the development of a method of estimation for the Portuguese case that may be used on a regular basis. The procedure developed is based on the odometer readings made in vehicle technical inspections. The method was applied for the estimation of the national road traffic volumes for the years of 2004, 2005 and 2006. The results include the first estimates at national level of VKM disaggregated by vehicle category and road type, thus enabling a better understanding of the travelled distances by these key variables, as well as permitting a comparison with previous aggregated estimates.