This synthesis will be of interest to geotechnical engineers, highway designers, construction engineers, planners, and others interested in constructing or widening highway embankments on problem foundations. Information is presented on site investigation and testing and on the various construction alternatives that are available when a highway must cross a problem foundation site. Construction over problem soil areas requires extensive site investigations and comparative design analyses to evaluate alternatives. This report of the Transportation Research Board updates and expands synthesis 29, which was published in 1973. It discusses the treatments and construction procedures that can be used to construct highway embankments over areas of soil that would otherwise not support such embankments. It describes site investigations, design analyses, and the kinds of treatments currently being used, including where they are applicable and the advantages and disadvantages of each.  The report for this topic can be purchased at https://www.trb.org/news/blurb_detail.asp?id=3410