Results of measurements of both the direct and the residual effects of heavy-vehicle loading of an arch with a 12-m (39-ft) span of corrugated metal and soil constructed as an overpass are presented. Both in-plane stress and vertical deflection of the arch are reported for 70-tonne (77-ton) and 290-tonne (319-ton) trucks positioned at various locations over the arch. The residual effects are shown in terms of a graph of cumulative deflection versus construction and service history. The heavy vehicles caused considerably more permanent deflection of the arch crown than did the 2.1 m (6.9 ft) of soil cover above crown level.(Author)