AbstractThe problem of placing bridges to alleviate congestion in a heavily loaded local-area computer network is briefly described. It is suggested that the generalization to that of placing transfer centres in other situations in which demand is arranged linearly may also be profitable. In order to obtain a better understanding of the problem, this paper concentrates on models in which demand is proportional (that is, the traffic intensity from one user to another is proportional to the product of their activity rates as measured by the traffic each produces). The results are rather surprising, it being demonstrated that the extent to which congestion can be relieved is severely limited.