Asian Transport Studies, Volume 3, Issue 4 (2015), 362–377. © 2015 ATS All rights reserved 362 Decision Principles for Routing Strategies: Games against Nature and Demons Jan-Dirk SCHMÖCKER a , Achille FONZONE b a Department of Urban Management, Kyoto University, Kyoto, 615-8540, Japan; E-mail: schmoecker@trans.kuciv.kyoto-u.ac.jp b Transport Research Institute, Edinburgh Napier University, Edinburgh, EH10 5DT, UK; E-mail: a.fonzone@napier.ac.uk Abstract: In this paper we firstly review general decision principles under uncertainty and apply them to route choice decisions. Risk-averse behaviour leads to the description of route choice a game. The difference between games against demons and nature are pointed out by distinguishing when disruptions on the chosen route might be related to the traveller’s behaviour or not. It is argued that in many cases the traveller has some (limited) information about the connection between attack likelihood and routing, meaning that pure games against demons are rare for practical applications. The paper therefore extends the game theoretic literature on route choice by formulating a generalised model. The model allows for games against multiple demons and consideration that some links might be safer than others. It is shown that games against nature and the Bell (2007) model can be derived as limiting cases. Results are illustrated with an example network. Keywords: Risk-aversion, Game Theory, Route Choice, Incident Information 1. INTRODUCTION Decision making under uncertainty is a topic of wide interest, from philosophical questions to mathematical problems with a very diverse range of applications (e.g., Binmark, 2008; Gilboa, 2010). Applied to transport, and more specifically route choice in a network, uncertainty arises as travellers and dispatchers often have to consider a number of risks when choosing a route. There might be congestion, accidents, vehicle-break downs or natural disasters. These risks could result in delays or, worse, loss of goods and life. Therefore the nominally shortest or most attractive route may no longer be chosen if the fear of such incidents dominates decision maker’s concerns. The more a traveller is unwilling to experience such risks the more “risk averse” he is considered. Whereas a risk-neutral traveller would try to balance the potential risks and the risk-independent minimum operational costs of a route, for an extremely risk-averse traveller the possible consequences of incidents outweigh the fixed costs. The strategy of the traveller to counter the risk will therefore depend on the feared consequences as well as the likelihood of the incidents. In particular, he has to judge whether the likelihood of incidents will depend in any way on his route choice. If he/she assumes that this is not the case, route choice under risk can be considered a “game against nature”. The fear of natural disasters or generally unpredictable events are examples. For such games against nature different decision principles have been proposed, in particular aiming to  Corresponding author.