Abstract: The objective of this paper is to investigate the effect of spatial dimension of roadside structures in landscape design.The method,which is normally used in the architecture and art design research,is introduced into transportation engineering.Resultspresented indicate that when roadside structures are within 50 m beside highway,their dimension is highly sensitive to highway users;when structures are from 50 m to 100 m beside highway,people are relatively sensitive to their dimension;while the distance between roadside structure and highway edge is beyond 100 m,people's sensitiveness is relatively worse.This result is very useful to control space form.