scope:

This instruction applies to traction bonding arrangements on a.c. electrified lines where train detection is provided by 

• d.c. track circuits
• HVI track circuits 
• Audio frequency track circuits (e.g.TI21 or EBITrack)
• axle counters
• Reed track circuits

For the purposes of this instruction, traction (i.e. "Non-Signalling") bonds include:

• structure to rail bonds
• traction rail to rail bonds
• impedance bond centre plate connections (on all types of track circuits employing impedance bonds).
• OLE along track conductors, including earth wires, return conductors and associated connections to traction rails
• Return screening conductors and associated connections to traction rails
• Red Bonds

"Signalling" traction bonds may be defined as:

• Yellow bonds
• Impedance bond side leads (on all types of track circuits employing impedance bonds ) and are outwith the scope of this instruction.

It applies to all maintenance, renewal, and project situations (including stageworks).

Purpose

Clear direction is required that attendance of signalling staff and/or the re-testing of track circuits is not necessary when changes are made to the a.c. OLE (whether Classic or Auto- Transformer) traction return system for electrification purposes, which have no effect on the integrity or operating characteristics of the train detection arrangements.