This chapter of a collective book aims at presenting the basics of decision making under risk. We first define notions … of risk and increasing risk and recall definitions and classifications (that are valid independently of any … representation) of behavior under risk. We then review the classical model of expected utility due to von Neumann and Morgenstern …

Certain areas related to the topics under discussion here lie outside my field; for instance the evaluation of risk … powers to analyse the risk decision-making process over some years now. …

consequences. By properly assessing the outcomes involved - especially those concerning human life - economic theory of choice … under uncertainty is expected to help people take the best decision. However, the widely used expected utility theory values …

Since von Neuman and Morgenstern's (1944) contribution to game theory, a rational decision maker will rank risky … the probability that he wins the bet is given by its expected utility. Probalities are precise objects to model risk, but … the way they do it is incoherent (Dubois and Prade (1988)). A familiar object in fuzzy set theory is the one of necessity …

congested road network. Drivers vary in their degree of risk aversion with respect to travel time. Four information regimes are … ranked in general. Free or Costly information can decrease the expected utility of drivers who are very risk-averse, and with … sufficient risk aversion in the population the aggregate compensating variation for information can be negative. …