The building of the Wall rendered Peglau’s dissertation useless. He had developed a braking system for the Berlin suburban railway circuit, but this was made redundant by the Wall. Karl Peglau’s life was closely interlinked with history. He spent 30 years working as an executive traffic psychologist for the medical service of the East German transportation system. In this position, amongst other things, he developed analytical procedures for ascertaining roadworthiness, as well as several guidance symbols for regulating traffic flows and for increasing traffic safety.