Corruption has been reduced a lot due to e-ticketing for the sale of tickets and their purchase by common people for travel. It has been effective at large.
However, there are possibilities of corruption in relation to the establishment, infrastructure, facilities, computers, software, etc. This has to be handled differently.
Corruption is possible when a booking agent or clerk or a ticket inspector can demand money in some situations.
It is possible that agents block tickets in advance and release them at a higher price. There is unaccounted money transaction due to such activities. However, if people stick to proper ways of booking on line through honest agents or official agents, then there will not be corruption.
There is inaccessibility due to lack of infrastructure and cost at rural areas. In such cases corruption is possible. Also, when there are some tickets available on trains and many people ask for allotment of the remaining vacant seats, there is a possibility.
There is an official provision for some allotment of seats by some persons. This is misused by the officials or employees to get extra money (they may call it commission rather than bribe) for allocating those seats.
Due to the awareness of people and their spirit to fight against the corruption can only eradicate it.