RULE 58. STARTING TIME.  (a) For regular helper service assignments a three-hour period shall be designated within which the assigned helper engineer may be called on duty at any time, payment for the trip to begin at time required to report for duty.  

(b) When regularly assigned helper engineers are called to report for duty after the designated three-hour period, payment for the trip shall be computed from the expiration of the three-hour period.

(c) When regularly assigned helper engineers are called on duty in advance of the designated three-hour period, the service shall be considered as an extra service trip for which a minimum day will be paid. When called on duty in advance of the designated three-hour period and the time on duty extends through and beyond the three-hour period, the extra service trip will be considered as ending and the regular trip as beginning at the expiration of the designated three-hour period. When the extra service trip in advance of the three-hour period is completed prior to the beginning of the three-hour period and no other service is performed on that date Rule 57 shall apply. 

(d) The designated three-hour period may be changed at any time upon 48 hours’ advance notice. 

(e) This rule shall apply only to regular helper service assignments.