The above temporary Redcliffe Flyover, near Temple Meads, shows how traffic can hop over tram lines under construction.
The Edinburgh track as is well known was very expensive and disruptive to install because what was chosen was essentially a standard heavy rail type track system, which required full removal and re-location of buried services, and which then necessitated a 450 mm depth slab to be cast. After the thick concrete base 450 mm was laid, tied sleepers placed on that, and these encased in more concrete.
Difficult to see how worn track will be replaced, but meantime Siberian iron-ore trains could probably be supported along Princes Street. This installation method also required all the services ( in unknown positions) to be moved – which is why the massive 450 concrete base was used to fill the void so created. This is potentially not necessary with some other track systems below. However apart from option (0) and (1) below, these have yet to be proven apart from the sleepers on sand approach. With all these approaches it is hard to see why services need to be diverted – at the very worst trams can simply stop at any new ground opening, and shuttle back and forth on each side of the excavation which is what happens in Zurich, and no doubt other trammed cities.
An alternative to closing tram tracks during service acces is to divert the tram using temporary tracks – click here
Potential alternatives to the heavy rail approach as used in Edinburgh:
Note: most of these alternatives are likely to require fewer buried utility diversions, and can safely bridge fragile vaults such as in Bath, unlike buses that damage them, as they create a much lower bearing pressure than a bus.
Also the lives of buried services is prolonged for the same reason.
(1) This is highly successful and proven in practice. TIG/m low insertion depth track – can be as little as 180 mm (7”) depth x 11 ft groove
(2) Succesfully demonstrated for 30 years in Sheffield. LR55 – low impact track
Full presentation of LR55 – http://www.lr55.co.uk/
LR55 has lower ground pressure under the rail than a bus: https://bathtrams.uk/8152-2/
The track shown below can be installed very quickly, one track at a time and does not disrupt traffic, by the machine shown below cutting a groove in the road in Bath. The patent holder is willing to share the technical and test data that supports LR55 claims, including testing up to 80 tonne axle loadings, and since 1996 in Sheffield operation without the need for maintenance.
The above type of machine, pictured in Bath, can cut one groove at a time without disrupting traffic and without service diversion.
The machine above cuts two grooves, one at a time, ie on separate days, with a plate covering the groove temporarily. Later the precast track is inserted and concreted in place, again covered with a plate while it sets. Then the plate is removed. Thus a small area of road about 6 m long , which rapidly progresses along the road is sterilised Wholesale road closure is not required and it can be done outside peak hours as above in Bath. Furthermore, utilities do not in general need to be moved as they are a) below the level of the track, b) access can still be gained through the two tracks, c) the track prolongs the life of buried services due to lower pressures from passing HGVs
Cross section of LR55 tracks which can be installed one at a time at night, minimising traffic disruption
Details of installation process
A single pass excavator creates a trench 400mm wide and 200mm deep. Pre-cast concrete foundation troughs in 6m lengths for straight tracks, are laid directly onto a bedding layer compacted to line and level. The troughs are initially linked together by ‘hairpins’ between adjacent ends. The troughs are then sealed into the pavement. The LR55 rail, welded into long strings, is laid in the trough, either using wedges of pre-cured PU grout, or clamp stands, to achieve line and level. With the achievement of line and level as a two-stage process, much higher precision can be achieved than with sleepered track. The final bonding grout is then injected under the rail to ensure full adhesion between the rail and trough, and between troughs. The exposed surface of the PU grout can be sprinkled with an aggregate to improve skid resistance for road vehicles using the same alignment.
Troughs are laid in advance of the rails and temporarily plated over until the rails are ready to install. By this means a complete installation of four rails for a double track can be completed at the rate of about 400m or more per week. By the use of several track installation teams a 20km route can be completed in less than 6 months, if there are no road traffic management issues.
Other utilities are usually 400mm or deeper, and access to them is possible between rails. The track is self-supporting over trenches 1m wide, allowing utility companies to lay new under across tracks without disrupting services.
The foundation trough sits on a compacted bedding layer about 20mm deep with a CBR of 10%. The trough is bound into the pavement by asphaltic sand or a similar compound. The LR55 rail is fixed into the trough with a polyurethane grout. This has both bonding and resilient qualities, which significantly reduces low frequency vibrations by about 30dB, and noise by 10dB. Because the LR55 rail is continuously supported, a smoother ride is provided for rail vehicles (and passengers), and the formation of rail head corrugations is significantly reduced.
The foundation trough transmits the wheel load into the pavement bearing course at a lower pressure than would be experienced from a passing HGV tyre.
The above track, acts like a heavy military tank track which by spreading the load over a large area means that the pressure below the track is less than that from the single line concentrated pressure from a bus or hgv. The beam acts like a lintel which means the cellar beneath Bath are subject to less force than from a bus or hgv
Transition of LR55 track on the left to conventional sleepered rail on the right. This has been installed as part of the Sheffield Supertram for 15 years.
Full presentation of LR55 – http://www.lr55.co.uk/
LR55 has lower ground pressure under the rail than a busl or HGV: https://bathtrams.uk/8152-2/
(3) P-CAT – low impact track slab
(4) Coventry Ultra Light Rail
The Coventry Very Light Rail project is currently investigating how to create a low cost trackform for the light rail carriages already in development, thanks to £1.5m funding from West Midlands Combined Authority (WMCA), secured by CCC.
Above – Warwick / Coventry track system….
This project aims to revolutionise affordable public transport in towns and cities.
So far in the Coventry Very Light Rail project, Engineers from WMG, University of Warwick have worked with TDI to design a battery-powered light rail vehicle for Coventry City Council. The long term objective is that it will become an autonomous vehicle that can hold 50 passengers and work like the London Underground system, where there is no timetable and people can hop on and off.
The vehicle will be lightweight in design using a multi-material approach. Due to being battery-powered there will be no overhead power supply, which is both costly and unsightly
However researchers are now about to embark on their next venture of the VLR project, as they have received £1.5m via CCC to develop a low cost trackform for light rail. Engineers at WMG will work with Coventry City Council and a major French civil engineering company – Ingerop Conseil et Ingénierie.
The ultimate goal of the track project is to design an affordable trackform that can be easily removed and will reduce impact on utilities, saving hundreds of thousands of pounds digging up roads and moving gas, electric, telecommunication and sewage systems, which is currently the process for building traditional tram systems.
(5) Ultra Light Rail Partners Trackbeam
(6) – Sleepers on sand as per The Hague
Track system below in Den Hag, build on sand to permit easy access to services
The photo above was taken in The Hague, and shows track being worked on while busy tram traffic is underway. The base is merely compacted sand.
HTM is the tram operator in Den Haag (The Hague). They seem to be able to use very simple track construction, ands it works. I have also seen it in Amsterdam. The concrete blocks take the load into the sandy substrate. As the rails are strong girders, they spread the load. They do of course use the traditional tie-bars to maintain gauge. Why do we go for so much more complication? They also don’t bother about track insulation, so why do we make such a fuss? The ride in Den Haag is excellent. Until recently the trams were PCC-based. A great smooth, quiet ride, like floating!
(7) Concrete beam – German city of Kehl, near Strasbourg
The German track system above, appears to be a very cheap, low depth construction method in Kehl, Germany. But it needs a lot of road excavation and will take weeks to install, to allow the concrete to cure. Could Bath cope with that level of disruption – perhaps in certain routes?
|30 Mar 2023, 15:32|
They do in Den Haag! The same sort of construction is used both in-street, and on grassed reservations. I saw it on the LRTA AGM weekend a few years ago. I also saw it in Amsterdam in the 1970s, where the idea of a new tramway being constructed seemed rather wonderful to British eyes!
The thing with Den Haag and Amsterdam, and many other European tramways, is that they have been doing it for years, and don’t start from scratch like we do; and try invent something better! Network Rail typifies our approach to things, ignore what was done in the past, and come up with something as mad as the GWR electrification!
A problem with us is lack of in-house knowledge and common sense, and going out to “consultants”, that seem to have no knowledge themselves!
8) A continental no-gauge bar system
11:15 (7 hours ago)