Incorrect statement I'm afraid. The ORR's position on not installing more third rail is purely on Health & Safety grounds. The existing system does not confirm to the Electricty at Work Regulations (1989) in that the live conductor is exposed to touch. Systems that may have shrouded conductors with bottom or side contacts could be deemed compliant but to change part or whole systems would be cost prohibitive.
And yet the Electricity at Work Regulations declare traction supplies to be out of scope.
The ORR has decreed that there will be no third rail simply because they decree it.
Just like they tore up the 25kV standard because they decreed it should be so.
They are not interested in running an economic railway, they want a "proper" one.
(Paragraph 116 of the Regulations states that tramway and railway operators have developed techniques and safe systems of work which meet the requirements here, and Paragraph 119 describes that such warnings can include signs and the like where physical isolation is impossible)
Also, give the state of the 25kV programme, a shrouded third rail system would still be cheaper than desperately trying to resuscitate it.
Agreed it, they reckoned 3rd rail is about 7-8x more problematic than OHLE for electrocutions.
A third rail installation of the current type is.
However there are numerous ways to reduce the risk substantially without abandoning backwards compatibility.
And even with those risk levels, given the ludicrous costs of 25kV...... the risk may still be ALARP.
EDIT:
Every day that electrification does not occur, people die from air pollution, and more carbon dioxide is emitted that we cannot afford to be emitting.
The ORR has conducted no work on ways to improve the safety of third rail installations and has simply decreed that there is to be no further installation.