The Taiwan High Speed Railway is currently one of the world’s largest BOT infrastructure projects. Due for completion in 2003, the railway runs down the western side of Taiwan linking all the main centres of population. A major constraint on the design of the viaducts is the interaction between the track and the structure during the operation of the trains, in particular when trains must brake to a halt from the 300 km/h operating speed under the service design earthquake. The paper describes a series of studies undertaken by the Authors’ firms to confirm the design criteria and the analysis methods that are to be used for the detailed design of the viaducts. These studies comprised non-linear analysis of the track and viaduct structure system under the actions of temperature variation and traction and braking, and multiple input non-linear time history analysis for the response under earthquake loading.