This paper deals with second-best one-route congestion pricing in case of an untolled alternative. Using a two-link network simulation model, the effects of various demand and cost parameters on the relative efficiency of one-route tolling are analyzed. It is investigated whether the existence of costs of congestion charging may be a reason for one-route tolling to be more "overall efficient" than two-route tolling. Finally, the efficiency of revenue-maximizing one-route and two-route tolling is discussed. © 1996 Academic Press, Inc.