The London Transport Rulebook
The origin of standardized rulebooks is covered elsewhere on this website.
This page relates to how the special circumstances of an underground electric railway were accommodated and how the pendulum swung between the perceived need for specialist publications on the stand alone lines and the need for standardization with the main lines with whom the Underground interworked.
More recently the general feeling of the rulebook approach being unsatisfactory has emerged, with the rulebook now replaced by a working reference manual.
This solution is also not perfect!