back into the Block Instrument which again restores the total number of tokens to 70.These enables the Block Instruments to be normalized and are now ready to dispatch another train in the block section form either direction.
It should be remembered that before giving TOS to the station in rear, the station in advance shall verify that the train has arrived complete.
Token-Less Block Working on Single Lines:
On single lines which see heavy traffic, token-less block working has been introduced which also uses Block Instruments of a different type and relies on Occupation and release of track circuits to ensure safe working of trains. This type of block working saves time to large extent and in this type of block working the Advance Starter being taken Off constitutes the Authority To Proceed to enter the Block Section.
Disadvantages of Absolute Block System:
As seen from the above example to move a train from one station to another several instructions have to be followed before making a move. This is fine in the sections where traffic density is low but in case of suburban traffic as in Mumbai where there are trains scheduled every three minutes, this system is certainly not feasible.
Possibility of accidents due to negligence on the part of human beings.
To overcome the above shortcomings Automatic Block System is followed in higher density traffic areas such as in Mumbai suburban traffic.