Current research on thermal effects on guideways has addressed many aspects of the behavior of guideways using two-dimensional models. The two-dimensional models are acceptable for existing guideway designs, in which cross sectional shapes are uniform along the length of the guideway. However, three-dimensional models are necessary for a modular design, in which the track structures that interact with Maglev vehicles are made separately and are assembled into the support structure, and in which the cross sectional shapes are not uniform. A three-dimensional numerical model of the thermal environment, in which the effect of partial shading is taken into account, is implemented for the study of guideway behavior under various thermal environments. The numerical model of the thermal environment is calibrated to the experimental results under the thermal environment at Austin, Texas, and is extrapolated to predict the behaviors of guideways under the thermal environment in Las Vegas, Nevada, which is one of the candidate sites for the implementation and deployment of the high speed Maglev transportation system. This study addresses the suitability of a modular steel guideway design under such a thermal environment. Characteristics of the behavior of guideways under various thermal environments are identified, and the behavior of guideways under the effect of partial shading is summarized.