Selection of external cordon line 

1. The external cordon line should cover the area which is already built up and  also likely to be developed during the design period. 
2. The external cordon line Should contain all area of systematic daily life of the people oriented towards the city center and should effect be 'commuter shed '.
3. The external cordon line should be compatible with previous studies of the area of studies planned for future.
4. The external cordon line should be continuous and uniform in its course so that movement cross it only once. 
5. The line should intersect roads where it is safe and convenient to carry out traffic surveys.