Abstract
This article is a summary of a lecture on this subject by Mr. R.T Johnson of the California Division of Highways completed with further data. A survey is given of the number of lives that have been saved by the construction of motorways in California since 1949. In case of the same number of covered vehicle-miles on motorways the number of fatalities is about the half of the number on other roads. In case of the half of all fatalities errors and physical imperfections of the driver, alcohol usage. By the driver and technical defects of the car had an important influence.