Economic principle Optimal use of a transportation facility cannot be achieved unless each additional (marginal) user pays for all the additional costs that this user imposes on all other users and on the facility itself. A congestion toll not only contributes to maximizing social economic welfare, but is also necessary to reach such a result. (Vickrey, 1967, 1969; Carlin+ Park, 1970)Economic principle Optimal use of a transportation facility cannot be achieved unless each additional (marginal) user pays for all the additional costs that this user imposes on all other users and on the facility itself. A congestion toll not only contributes to maximizing social economic welfare, but is also necessary to reach such a result. (Vickrey, 1967, 1969; Carlin + Park, 1970)