law: Railways Act, 1989
  130. Definitions.  
  In this Chapter, unless the context otherwise requires,- 
  (a) the employment of a railway servant is said to be
  
  "continuous" except when it is excluded or has been declared to be
  
  essentially intermittent or intensive;
  (b) the employment of a railway servant is said to be
  
  "essentially intermittent" when it has been declared to be so by the
  
  prescribed authority on the ground that the daily hours of duty of the railway
  
  servant normally include periods of inaction aggregating to fifty per cent. or
  
  more (including at least one such period of not less than one hour or two such
  
  periods of not less than half an hour each) in a tour of twelve hours duty (on
  
  the. average over seventy-two consecutive hours), during which the railway
  
  servant may be on duty, but is not called upon to display either physical
  
  activity or sustained attention;
  (c) the employment of a railway servant is said to be
  
  "excluded" if he belongs to any one of the following categories,
  
  namely:- 
  (i) railway servants employed in a managerial
  
  or confidential capacity;
  (ii) armed guards or other personnel subject
  
  to discipline similar to that of any of the armed police forces; 
  (iii) staff of the railway schools imparting
  
  technical training or academic education;
  (iv) such staff as may be specified as
  
  supervisory under the rules;
  (v) such other categories of staff as may be
  
  prescribed;
  (d) the employment of a railway servant is said to be
  
  "intensive" when it has been declared to be so by the prescribed
  
  authority on the ground that it is of a strenuous nature involving continued
  
  concentration or hard manual labor with little or no period of relaxation.