Lead: 
The distance between the source of availability of material and the construction site is known as Lead. Lead is measured in km. The cost of conveyance of material depends on lead. The environment lead on the metalled roads are arrived at by multiplying by a factor as follows: 
For Sandy Tracks – Lead × 1.4 
For Metal Tracks – Lead × 1.0 
For Cartze Tracks – Lead × 1.1