This chapter illuminates ways in which cost-benefit analyses as practiced in most countries tend to depict unsustainable transport solutions in urban regions in a too positive light. The valuation of negative environmental impacts tends to be grossly underestimated, particularly effects such as CO2 emissions. The discounting of future effects aggravates this by seriously diminishes long-term environmental impacts. Induced traffic from road construction in urban areas is often underestimated, especially long-term induced traffic resulting from urban sprawl facilitated by easier access to farther-away destinations. Moreover, environmental impacts pertaining to the construction period are often neglected or underestimated. Due to the method’s tendency of underestimating adverse environmental effects while overestimating travel time savings, cost-benefit analyses tend to legitimize a high spending of society’s resources on road construction and delegitimize environmental opposition against road capacity expansion.