Abstract: Making use of Yin and Graham’s 1-D elastic visco-plastic model which can predict both the primary and secondary compression, the formulae of calculating the long term settlements at the end of the road operation period and/or during road operation period induced by the trapezoidal periodic loading are theoretically deduced. The theoretical results show that the permanent 1-D settlement of road embankment under period loading can be calculated without regard to the solid-fluid coupling when the condition of ground drain is improved by some ground treatment. The formulae show that the long term and post-construction settlements are not only related to both stress states and stress history such as initial effective stress and over consolidation ratio, but also related to physical indices such as swelling index and compression index and creeping coefficient. In the cases, the total settlement of road embankment at the end of its operation period is numerically evaluated by making use of the long term settlement formulae provided in the paper, and the critical settlement of road embankment at the start of its operation period is further determined, which can provide the reasonable settlement standard for determining the start time of road pavement construction in expressway road.