The Departmental wagons expressed as a percentage of total wagons was maximum during:

In 2002, the percentage of departmental wagons to the total wagons = $$\frac{9536}{216717}\times\ 100\ =4.4\%$$

In 2003, the percentage of departmental wagons to the total wagons = $$\frac{10718}{214760}\times\ 100\ =\ 4.99\%$$

In 2004, the percentage of departmental wagons to the total wagons = $$\frac{11388}{227752}\times\ 100\ = 5\%$$

In 2005, the percentage of departmental wagons to the total wagons = $$\frac{10964}{222379}\times\ 100\ = 4.93\%$$

Thus, the correct option is C.