In a bridge project, several alternative design solutions can be functionally equivalent for the designated location. Today’s bridge constructions highly rely on the non-renewable resources, the consumption of fossil fuels, and the intensive usage of concrete. This urges designers to explore the new design options to mitigate the associated environmental burdens. When comparing to the concrete slab frame bridges (CFB), the soil-steel flexible culverts (or soil-steel composite bridge, SSCB) show advantages in ease erection, low maintenance as well as the competitive cost. However, its environmental performance has never been studied. This paper intends to compare the environmental performance of these two bridge types through the whole life cycle, based on 8 selected cases in Sweden. Unlike previous studies only limited to few impact indicators, this study comprehensively covers a wide range of indicators: including eleven types of mid-point impact categories, the cumulative energy demand (CED) and the associated cost. The construction phase, which seldom included previously, is a specific focus in this paper. The results find that: 1) the SSCBs show advantages over the CFBs in most of the investigated indicators; 2) the construction phase, when explicitly evaluated, may take up to 34% of the total life cycle environmental burdens; 3) the environmental performance of a bridge is closely linked with the bridge type selection, multiple indicators in the environmental domain, designers' preference, the construction phase, as well as the time schedule constraints.