Abstract
In this article the relationship between street lighting and traffic accidents at night is studied. The number of accidents at night increases every year. (1955 - 27%, 1965 - 34%) In built-up areas: 25,3%. Outside built-up areas:9,6%. This study is based on the number of accidents happened at night and by day in the Metropolitan Police District. Between 1955 and 1965 the number of accidents at night increased with 6% p. veh./km. in this area. The costs of all accidents in Great Britain in 1965 amount to 246 mil. pounds. (107 mil. pounds for accidents at night). The economic justification of lighting improvement is described.