This paper describes work carried out to improve the design of bridge expansion joints and thus increase their durability. The current Japanese design specifications for joint loading are compared with real data on vehicle loading obtained from measurements on an urban expressway. The impact coefficient and the contact pressure on the joint surface are also estimated and compared with those given in design specifications. Impact coefficient is normally taken to be 1.0. In order to confirm the validity of this value, the effects of road condition, vehicle running speed, and vehicle overloading upon impact were also studied in the laboratory. Field tests were carried out to confirm these findings using a cast aluminium alloy expansion joint installed on a new bridge. Both static and dynamic load tests were carried out using a dump truck with a gross weight of 200kN. The static tests were conducted for two different loads, using the front tyre of the truck. In the dynamic tests, truck speed was increased in stepwise fashion from very slow to 60 km/hour. Once the bridge was opened, the actual stresses in the bridge caused by the traffic were also monitored. The results indicate that the expansion joints used for the test have an appropriate level of safety. For the covering abstract of the conference see IRRD 858334. The French title of this paper is:- Durabilite des joints de dilatation des ponts. The German title of this paper is:- Dauerhaftigkeit von Fahrbahnuebergaengen.