The Indian railways are broadly divided and sub-divided into zones, divisions and departments, each controlling a particular function. Each department has staff at various levels. The highest are the Group A officers, while the lowest in rank are the Group D staff members.

Group A
UPSC – Group A officers are recruited by UPSC
Civil Service Examination – Indian Railway Traffic Service (IRTS) and the Indian Railways Accounts Service (IRAS)
Combined exampapers.info/category/engineering" title='Read more about Engineering'>Engineering Service – Indian Railway Service of Engineers (IRSE), Indian Railway Service of Electrical Engineers (IRSEE), Indian Railway Services of Signal Engineers (IRSSE) and Indian Railway Store Service (IRSS)

Group B
Group B officers are directly promoted from Group C.

Group C
Group C officers are recruited through the Railway Recruitment Board (RRB). The 19 Railway Recruitment Boards (RRBs) have been functioning as prime recruiting agencies for all Zonal Railways, Production Units and other extra Zonal units of the Indian Railways. Each Railway Recruitment Board is catering to the recruitment needs of the specified jurisdiction on the Railways.