Principles of the staged construction planning on highway.

Staged construction in this study is to be one of the construction methods of roadlanes;generally this planning is applied to final 4- lane highway construction in which the first stage is opened to traffic as two- lane- two way highway, and while allowing through traffic the second stage is supplemented by adding the next 2- lane- roadway.Although staged construction is recognised economical in case of low traffic volume, it brings forth some problems to be checked upon.