Vogel’s Approximation method for a balanced transportation problem starts with
the calculation of penalties (the difference between the second minimum and the first
minimum costs) for all rows and columns. Then it allocates as many units as possible to
the least-cost cell in the row or column having maximum penalty. Then the allocated
row/column is deleted, penalties are revised and procedure repeated successively until all
units are supplied.
Shimshak et.al. [9] propose a modification (SVAM) which ignores any penalty
that involves a dummy row / column. For example, if there is dummy columns in the
cost –matrix, the penalties are ignored not only for the dummy column, but also for all
the rows since the calculation of row-penalties involves the dummy column. Goyal [3]
suggests another modification (GVAM) where the cost of transporting goods to or from a
dummy point is set equal to the highest transportation cost in the problem, rather than to
zero. Ramakrishnan [7] consists of four steps of reduction and one step of VAM.
Balakrishnan [5] suggest further modification in SVAM.
Zero Point Method is very useful for determining an optimal solution for both
crisp and fuzzy transportation problems. This method requires few step by step
procedures to get an optimal solution for the given Crisp or fuzzy transportation problem.
To illustrate this procedure, let us consider the following problem to describe Pandian
and Natarajan[6] method.
We come to know that, it is not possible to solve the above problem using Pandian and
Natarajan [6] method. It means there is no solution for this problem. Pandian and
Natarajan [6] method, has few step by step procedures on that step4 says, check if each
column demand is less than to the sum of the supplies whose reduced costs in that
column are zero. Also, check if each row supply is less than to sum of the column
demands whose reduced costs in that row are zero. Due to this condition this problem as
no solution.
If we replace “less than” in step4 by “less than or equal to” and apply remaining
procedures of zero point method, we get an optimal solution.