Not quite, it could be best described as a 125mph capable OLE system; attainable with subtle modifications.
The OLE on the MML was one (if not) the first installation of auto-tensioned Mk3B in the UK. The system has the correct contact and catenary wire tensions (11kN/11kN) and does not need re-tensioning if single pantographs of the HSP or HSX type are used. Its issue is that where STC's are in situ these the steady arms are of the shallow curve type, and not the deep curve type predominantly seen on headspans. The shallow curve type (when fitted to STCs) provide insufficient uplift for anything greater than 110mph; these would be an issue around the Ampthill Tunnel area where the HST speed is 125mph on both the Down and Up Fast Lines as alluded to elsewhere in this thread. There are also several other issues on the MML:
- Bridge grading and clearances at fitted overbridges, it is assume that these were setup for no more than 100mph when installed - records are unclear!
- Clearance from the contact wire to the lowest spanwire, which is substandard in certain headspan areas
- Presence of split span wires between the Fast Lines and Slow Lines - a case in point is around Stewartby
- A general drift away from the correct heights and staggers for anything more than 100mph.
The ECML uses STC's with drop brackets and deep curve steady arms. When correctly setup these can accommodate >125mph operation and have 250mm - 300mm uplift - whereas the shallow curve type only give something like 150mm.
West of Stockley Viaduct Series 1 is installed, this can be operated at up to 140mph with the correct pantograph types, but not where any overbridges use the fitted GFRP bridge arms - these are limited to 125mph to avoid forming hard spots in the contact wire.