Samenvatting
In the period 1975-1978 an intensive o/d survey was carried out among passengers on buses and trams of the Rotterdam Public Transport Company RET. The study resulted in a report on origins and destinations of trips, trip lengths and purposes, and connections where people have to change. About 250000 people boarding public transport vehicles were examines which boils down to 50% of the patronage. This was the reason of the interviews being spread over 4 years. The article gives a statistical justification of this procedure.