Tollplazas on highway.

Highways toll plazas are based on the principle "economics of scale"

    Which states that percentage change in average cost of production following at 1% increase in output.

    It is the cost advantage that an enterprise obtain due to their scale of operations.

If we consider making a highway it cost a lot of fixed cost. The initial investment is very high. Though government took the initiative and execute the plan in to action.

   Once the highway is made, government started set up toll plazas over it. Which basically collect some amount of money from those who are using those highway.

    As highway are used to set up in those busiest and most populated areas where there is greater chance of people using this highway. Therefore after setting up all those toll plaza government started charging some amount on the basis of size of vehicles passing through the road or highway. This is done to collect the expense made to build the highway.

     Since the user of highway is quite a large number therefore the average cost reduces per people. It bring down the average cost and with the time it reduces to zero.