Notes and comments Applying activity-travel data for the assessment of vehicle exhaust emissions: Application of a GPS-enhanced data collection tool Carolien Beckx a, * , Luc Int Panis a , Davy Janssens b , Geert Wets b a Flemish Institute for Technological Research, Boeretang 200, Mol 2400, Belgium b Transportation Research Institute – Instituut voor Mobiliteit (IMOB), Hasselt University, Wetenschapspark 5 bus 6, B-3590 Diepenbeek, Belgium article info Keywords: Automobile emissions Travel behaviour Global positioning system Personal digital assistant abstract This paper describes the development of a global positioning system, enhanced data collec- tion tool for the assessment of vehicle exhaust emissions. This involves the collection of activity and travel data on a personal digital assistant with built-in global positioning sys- tem receiver. By converting the second-by-second global positioning system based travel data into emissions, estimates are made of the exhausts produced by individual vehicle trips. Differences in travel behaviour and vehicle emissions were examined by gender and trip purpose. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction National and local policymakers are increasingly recognizing the importance of source-related measures to reduce the environmental impact of transport. Unlike technological measures, source-related measures intervene in an earlier stage of the problem, an approach that is in accord with the current policy of the European Environment Agency (1999) where increasing attention is given to the ‘driving forces’ of environmental problems. Regarding road traffic air pollution, focusing on the source of the problem means concentrating on the travel behaviour of people. Why are people traveling by car? Which type of activity or person is responsible for producing most of the traffic air pollutants? Good qualitative information about people’s travel behaviour should be able to provide the answers to this kind of questions to policymakers and enable them to assess the impact of a policy intended to change travel behaviour on traffic related air pollution and to establish a source-related policy. This paper considers a data collection tool that gathers detailed information about the travel behaviour of people and indirectly provides information on the vehicle emissions that are produced during every vehicle trip. The approach combines the use of an activity diary on a personal digital assistant (PDA) with global positioning system (GPS) receivers to gather detailed travel information from respondents in a travel survey. 2. Background on the use of travel data for emission assessments Travel data can be collected for multiple purposes and on different scales. While either a macroscopic or a microscopic approach can be used to calculate the emissions from vehicle trips, here we only focus on the latter. On a microscopic scale vehicle emissions are calculated based on instantaneous vehicle parameters including speed and acceleration. The approach is therefore able to assess the impact of changes in driving behaviour on emissions. Examples of the microscopic emission models are MODEM (Jost et al., 1995), the VT-micromodel (Rakha et al., 2004) and the VeTESS 1361-9209/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.trd.2009.10.004 * Corresponding author. Tel.: +32 (0) 14335958; fax: +32 (0) 14321185. E-mail address: carolien.beckx@vito.be (C. Beckx). Transportation Research Part D 15 (2010) 117–122 Contents lists available at ScienceDirect Transportation Research Part D journal homepage: www.elsevier.com/locate/trd