The book "Rationality of Urban Road Networks" offers a comprehensive analysis of the planning and efficiency of urban road networks. It highlights the common issues of detours and inefficient routes in cities worldwide, where actual travel paths are often significantly longer than the direct distances between starting and ending points. By introducing various measurement scales, the work enables a quantitative assessment of road networks and identifies potential areas for improvement. The techniques presented have been applied to 14 carefully selected cities, including metropolises like London, Paris, and Tokyo, providing a valuable comparison of network quality among these cities. This specialized book is aimed at urban planners, traffic engineers, and researchers interested in optimizing urban mobility.