Decision making and strategies in an interaction situation: Collision avoidance at sea Christine Chauvin a, * , Salim Lardjane b a University of South Brittany (UBS), GESTIC, Centre de Recherche, rue de Saint-Maude ´, 56321 Lorient Cedex, France b Institute of Biomathematics and Biometry, GSF – National Research Center for Environment and Health, Ingolsta ¨ dter Landstrasse 1, 85764 Neuherberg, Germany Received 9 March 2007; received in revised form 4 December 2007; accepted 13 January 2008 Abstract This paper aims at analysing decisions which are actually made by watch officers onboard ferries in the Dover Strait. More precisely, it aims at characterizing the generic situations in which several courses of actions are available and iden- tifying the strategy underlying an action choice. Relying on the RPD model of Klein [Klein, G. (1997). The recognition- primed decision (RPD) model: Looking back, looking forward. In C. E. Zsambok & G. Klein (Eds.), Naturalistic decision making (pp. 285–292). Mahwah: Lawrence Erlbaum Associates], it points out the critical cues, the goals of actors and the rules they use. Two sets of data were processed: motions of vessels observed from the vessel traffic system and verbal protocols recorded onboard a ferry with three watch officers. Logistic regression models show that different types of ships do not act in the same way: the slowest vessels tend to keep their course and speed, even if they have to move. The faster cargo ships such as ferries alter their course in compliance with the regulations. In some situations, a ferry may nevertheless follow informal rules. Onboard a ‘give way’ ferry, a watch officer may – in some conditions – alter his course to port rather than to starboard to reduce the course alteration and the loss of time. On board the ‘stand on’ vessel, he may perform an action in order to master the situation, even if the rule requires him to keep his course and speed. Ó 2008 Elsevier Ltd. All rights reserved. Keywords: Interaction; Decision making; Strategies; Ship handling; Collision avoidance 1. Introduction Maritime transport and travel has a relatively low death and injury rate when compared to road travel; in 2000, fatality risks assessed on the basis of the distances travelled in a particular mode was estimated at 1.1 for road travel (per 10 8 person km) and at 0.33 for ferry travel in Europe (Mackay, 2000). However, within a 1369-8478/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.trf.2008.01.001 * Corresponding author. Tel.: +33 0297874521; fax: +33 0297874500. E-mail addresses: christine.chauvin@univ-ubs.fr (C. Chauvin), salim.lardjane@gsf.de (S. Lardjane). Available online at www.sciencedirect.com Transportation Research Part F 11 (2008) 259–269 www.elsevier.com/locate/trf