A; gives the number of accidents between modes i and j in which i is the victim. It is
assumed not to depend on the number of vehicle kilometres driven by transport modes
other than i and j. a” stands for the willingness-to-pay (WTP) to avoid an accident of
type n. b, is the WTP of the relatives and friends of the victim to avoid an accident of
type n. a” and b” are the so-called ‘warm-blooded’ costs as opposed to the ‘cold-blooded’
cost category c” which consists of the pure economic costs (net output losses, ambulance
costs, medical costs, etc.) which are borne by the rest of society.
The marginal social accident cost (MSAC) of a car is the derivative of the TAC with
respect to the number of car km: