OHL Clearance on Croydon Tram

[Dr_Paul]

I was travelling the other day along Kingston Road by Merton Park station on the Croydon Tram and noticed that although there are signs warning that trams are crossing the road, there are none giving the height of the OHL. I've seen signs on railway level crossings on lines with OHL that give a safe height for vehicles, so I'm rather surprised that there weren't any on this busy road.

 

[Chris M]

Paragraph 20.2.1 on page 78 (PDF page 79) of Chapter 4 of the Traffic Signs Manual states

20.2.1. Diagram 779 [...] warns of a place where a road passes under an electrified overhead
power cable. It must always be accompanied by a plate indicating the safe maximum height
vehicle that can pass below the cable [...]
These signs are normally associated with overhead electric railway or tramway cables and
should be used at all such crossings. Because of the high voltage of certain cables, it is very
important to ensure that adequate warning is given even where cable heights are greater than
16’‑6” (5.03 m).

So it seems there should be signs where the road crosses the tramway.

 

[edwin_m]

However the current LRSSB tramway guidance states: http://lrssb.dev.codemakers.co.uk/resource/electric-traction-systems

The height of the contact wire or any other live part of the overhead electric traction supply system must not be less than 5800 mm above the surface of any carriageway at the maximum temperature of the wire. See Electricity Supply Regulations 1988 here. Any proposal to use a lower position (for example, because of an existing bridge) would require express statutory authority or an exemption from the Secretary of State for Transport.
...
Where the headroom below the contact wire is reduced, the safe height should be indicated on road traffic signs as seen in diagram 779 in the Traffic Signs Regulations and General Directions (TSRGD) here both in advance and also at the location of the reduction.

I interpret this as meaning that a sign is only necessary if this clearance is not achieved. Special arrangements are needed if a tramway crosses a designated High Load Route.

This particular guidance wasn't in force when Tramlink was built, but I can trace the same wording back to at least 2006 and I believe it is unlikely to have changed in the 1990s version (the old RSPG part 2 section G).