Track facts – Modern light-rail track

by

Kaiserstr

The recently built tramtrain line in Heilbron Germany

There has been much debate about the cost of track laying and the cost for new tracks for light rail or streetcars. The following will hopefully shed some light on how modern LRT (streetcar) tracks are laid on-street. With the interurban, of course, the majority of the route will be shared with other railways and the costs would be to upgrade existing tracks (relaying) and adjustments to switches. Portland Ore. give good insight on modern track laying principles.

The Portland streetcar is laid with girder rail, set in concrete, which is sturdy enough to handle the larger MAX LRV’s. The main problem is that the streetcar line has tighter turning radius, which the larger LRV’s can’t negotiate.

The continued nonsense about relocating utilities has more to do renewing utilities on the back of light rail construction, and making work for municipal employees than anything else.

Many alignments of new LRT systems are increasingly placed in public thoroughfare rights-of-way (on-street). For example:

· Portland – over 28%
· Sacramento – nearly 23%
· San Jose – nearly 56%
· Dallas – over 20%
· Salt Lake City – nearly 19%
· Tacoma – 100%
· Houston – 100%
· Minneapolis – nearly 22%
· Phoenix (planned) – over 95%
· Seattle (planned) – over 32%

As much as possible, construction methods and practices which have significant potential for lowering costs should be considered. For example, in the case of the Portland Streetcar, the shallow-slab construction method (see Figure 3) proved to be a major cost-saving technique for in-street construction. Instead of digging three and four feet deep, disrupting utilities, and rebuilding much of the street in the process, builders use a quick “cut and cover” European-style track system that goes down between 12 and 18 inches and is 6 to 7 feet wide. A pad is laid down, followed by a light layer of gravel, and then a special dual rebar side frame is laid into this shallow trench.

Each running rail is encased in a “rubber extrusion rail boot” to provide electrical isolation as a corrosion control measure. This covers the rail entirely wherever there is ground contact, and is then attached to the specially shaped rebar frame with dielectric fasteners. The boot also provides some basic level of noise/vibration attenuation. The boot-encased rails are held only by the concrete between anchor plate assemblies, which are placed at 3.0-meter intervals on straight track and broad curves, or at 1.5-meter intervals on curves sharper than 300 meters in radius. The fastener assemblies remain separated from the running rails by the rubber boots to maintain electrical isolation of the rails. There are no gauge bars.

A major advantage is the minimization of subsurface utilities relocation. Instead, a kind of “bridge” (the slab, carrying the guidance rails) is installed over utilities. This enables utilities workers to make an adjacent excavation, as necessary, to access under-street utilities for repairs or other servicing.

Slab depths are 300 mm (about 12 in) for the RI 52 girder rail used on streetcar construction for cars weighing about 30 tons empty, and 360 mm (14 inches) for RI 59 girder rail used where streetcar and “interurban” tracks cross. Prudent planning would suggest designing and building for future use of heavier, interurban-type vehicles, since these might ultimately be needed if the original system is successful. It’s far more difficult to upgrade under-designed trackage than to upgrade stations and procure larger vehicles. To accommodate the possibility of heavier, “interurban”-style LRT in the future, a slab depth of 18 inches is sufficient. If the design of the rail line is to be in a raised median, then a depth of 12 inches can be maintained, with the slab, rising in a media, six inches above the roadway.

Seems a whole lot simpler and cheaper than tearing up entire streets and moving utilities, but then, this is exactly what the SkyTrain lobby wants!

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6 Responses to “Track facts – Modern light-rail track”

  1. Justin Bernard Says:

    As a pro-LRT supporter, this is an excellent blog! Keep up the good work!

  2. mrjauk@yahoo.com Says:

    Would you mind commenting on Toronto’s newly proposed 15-km LRT line, which will reportedly cost $950 million? That works out to about $63 million/kilometre. You have previously mentioned that an LRT down Broadway could be built for $10 million/kilometre. Why is the cost so high in Toronto? Do you know if the planned route in Toronto is more/less difficult to build in than the Broadway corridor?

    Thanks.

  3. mrjauk@yahoo.com Says:

    Oops! Sorry for not including the link to the story in my first comment:

    http://www.theglobeandmail.com/servlet/story/RTGAM.20090515.wtransit0515/CommentStory/National/home

  4. zweisystem Says:

    First comment I can make about Ontario’s new LRT is; is it ‘greenfields’ construction and how much engineering is involved? being 3000 miles away I am not familiar with route etc.

    Second comment is; is this the total cost of the project, including debt servicing? As you know, the total cost for SkyTrain (including debt servicing) has never been revealed. In the USA, it is customary to give the total cost of a transit projects, including debt servicing, rather in BC in only giving the direct costs and hide debt servicing costs.

    Obviously, the high cost indicated a lot of engineering and it seems to me that in North America, new light-metro projects are camouflaged as LRT! Seattle is a good example of this.

  5. zweisystem Says:

    I have done some research and as I suspected, the new LRT line has some major engineering including a 1 km. tunnel and a large bridge over CN tracks. Also an expensive curb-separated median that is fully encased in concrete, for use of emergency vehicles is included. Factor these out and the cost comes down to a more reasonable $24.9 million/km.

    The $950 million quoted cost comes in at about $55.9 million per kilometre as there will be about 17 km of track, including almost 1 km of non-revenue track on the surface of Sheppard between the tunnel portal and Don Mills. This still much cheaper than than the $250 million per kilometre for subway construction and it will be in service in half to two thirds the time.

  6. Detroit's M1 Light Rail Line News and Developments - Michigan (MI) - Page 7 - City-Data Forum Says:

    […] […]

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