The following plot shows that development of driver, front and back-seat passenger deaths in Great Britain from 1969 to 1984. This plot illustrates the number of road casualties is decreasing for all types of people in the car, driver, front and read passengers

On 31 January 1983 a new law was passed making it compulsory to wear seatbelts. This may be the reason why we see a drastic decrease in driver and front-seat passenger deaths from 1982 to 1983. The boxplots below further confirm this statistical difference between the monthly road casualities before (indicated by 0) and after (indicated by 1) the law was introduced.