Wildlife crossing structures (WCSs) have been built on every continent, and interest in transportation agencies to mitigate barrier effects on wildlife populations is increasing. Many studies have published the results of monitoring and evaluation of WCS in technical or scientific venues. Yet there are several aspects of WCS implementation that merit examination and synthesis of current knowledge. These aspects include planning, design, evaluation, and policy process and are reviewed. Construction of WCS has surged in the last 25 years. Most WCS research has been conducted in temperate regions and developed nations, while Latin America, Asia, and Africa have lagged behind. Anticipated growth and ongoing highway investments, particularly in developing nations, coupled with resounding concern for preserving biodiversity and maintaining large-scale landscape connectivity, have generated interest in “smart” or green infrastructure such as WCS. Urgent work needed should address demographic filtering, including sex-age class selection of WCS types. There is a need to increase and expand training and capacity building, particularly in developing economies and nations that have less experience and exposure to established biodiversity safeguards. Further work is needed on methods of prioritizing conservation values and transportation investment in selecting WCS locations. Some important knowledge gaps include the quantification of genetic and demographic connectivity at WCS, research on the prey-trap effect of crossings, the utility of before–after-control-impact study designs, and developing engineering guidelines for WCS construction.