Automatic Block Signal (ABS) rules apply only where designated by?

• A. Timetable or Bulletin Order
• B. Form D line 2
• C. Interlocking
• D. Bulletin Order or Form D line 7

Answer: (A)

Automatic Block Signals are in effect only in the sections that the timetable or a Bulletin Order designates. That official designation tells crews exactly where ABS rules apply, so you follow ABS in those blocks and use other applicable rules outside them. The designation isn’t determined by an interlocking or by temporary instruction forms alone; an interlocking governs moves through junctions and may include ABS, but the official scope of ABS comes from the timetable or a Bulletin Order. Temporary forms (like Form D lines) can convey instructions, but they don’t establish the regular ABS territory.