A continuing experimental model study relating to the seismic resistance of large multi-span curved overcrossings is reported. A brief description of the microconcrete model, a 1/30 true-scale version of a hypothetical prototype, which was tested on the 20 ft x 20 ft (6.1 m) Shaking Table at the University of California, is given. The response of the model is described for a series of simulated seismic excitations applied (i) horizontally in the asymmetric longitudinal direction, and (ii) horizontally in the symmetric direction, both alone and also with simultaneous vertical excitation. The influence of expansion joint design on the seismic behaviour is the main parameter studied, with emphasis on the need for joint restrainers of adequate ductility, to effectively tie adjacent girders together. However, because of the severe damage caused by impacting at the expansion joints during moderately strong excitation, it is concluded that expansion joints should ideally be omitted from such structures.