The Western Approach road cuts a huge swathe through towards Lothian Road with 3 heavy rail connections & land that can be re-worked especially where the Slateford stabling sidings are & the original Caledonian Rqailway trackbed was still providing road access to The Slateford Yard along the original Caledonian Railway lines from Carstair/Shotts &c to Princes Street Station
I need to do some checking on the tangle of embankments and old station sites that weave all over the West side of Edinburgh
The residual embankment that parallels Russell Road still has the potential to restore an overbridge of the main route at the exit from Haymarket Depot and with the advantage of light rail/trams to use far more severe curve radii both horizontal and vertical and rail alignmemts & profiles plus lower axle loads (8-9 Tons vs 25 Tons for rail) The detail of flange and tyre profiles, was the topic of research in 1990 by Manchester Metropolitan University but this is equally reflected in how a heavy rail line needs to be modified and the tram wheelsets also modified to run tram trains
The tram derailment at Eastfield Avenue (on EDI site) after the collision with the long stay car park shuttle bus highlights an issue here, where tram tyres have reduced conicity, and larger back to back distance on the flanges. The 2008 Croydon tram crash (bus driver collided with tram becuase the changed traffic signals (from 1 day earlier!) had not been properly risk audited, and bus driver read a green signal on opposite side the tram track rather then the red signal directly ahead of the bus. RAIB has a report but not a formal investigation. The bus derailed the tram wich cuased it to run away and crash into a shop, The bus crashed into another shop & a passenger died when ejected through the window of the upper deck in 2008 this highlighted the hazard of buses & coaches having toughened glass windows rather then laminated glass, and this was a major factor in the death toll from the 2016 Croydon tram crash when the windows fell out & passengers were ejected
This means that points and check rails for tracks shared between trams and trains, need to have extension plates to engaage with the added thickness that has to be specified for the wheels on all trams, so the trams used for any tram train will need new wheelsets of these can be fitted to the current fleet
The other issue is that trams are operated by line of sight rather than block signalling with minimal regulation of movements, and other heavy rail operations can include approach release speed control plus the brake and power shut down as the right side failure when drivers fail to respond to vital signals
The lack of block section signalling & related protection saw 2 tram collisions in close succession at St Peters Square in Manchester, and I've been slightly concerned when looking out from the rear of trams in Birmingham and Manchester to see the following tram powering along at 50mph and only relying on the tram driver to stop before ramming into the tram I was on
In June 2016 the lack of a central control system with 3 separate bus operators on the Dunstable busway saw a 50mph rear end crash that put 19 people in hospital after a Centrebus driver failed to stop before hitting a Grant Palmer bus that had broken down, and shoved that bus 30 metres with the impact
So there will be many details to deal with when running trams on heavy rail systems. Not impossible but with the greater delivery of competent risk management for the railway compared with that clearly not (yet) seen with a road transport culture we have some big shaking up to deliver
For the best action the entire on street section of the original tram route, between Haymarket and Waverley should use the gound survey cor logs from the Caledonian Railway's project to build a 2-track railway UNDER Princes Street, which @arellcat helpfully researched. This can be delivered without having to close any of the roads for extended periods by using the system used in 1963 when Oxford Circus Tube station was built under the cross road (Oxford Street/Regent Street) as traffic continued to run over a steel umbrella
By running the trams under Princes Street the delays & conflicts with other surface level traffic are eliminated and the connections for the radial network connections made much simpler.with a multi track junction alongside Waverley Market to emerge in the centre of Leith Street Eliminating the messy detail around Picardy Place and going over, or under the London Road junction near Elm Row
The spur to the South can rise up in the centre of North Bridge before the historic span over Waverley Station
Much more to describe in detail elsewhere
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