When the “tram on tyres” or “rubber-tired tramway” technology first emerged in the early 2000s, it was positioned as part of the new Bus Rapid Transit (BRT) concept attracting interest at the time. The argument went that “BRT” was “just like light rail, but cheaper”, and the “rubber-tired tramway” was intended to demonstrate that a “tram” constructed with automotive/bus technology could be “guided” just as a light rail transit (LRT) tramway was guided by its track rails, and able to operate extra-long, multi-articulated buses smoothly and reliably just like the tramcars on LRT railways.
A number of cities have experimented with or adopted the technology, particularly in France, where cities like Nancy, Clermont-Ferrand, and Caen made the “tram on tyres” the centerpiece of their transit systems. Now, plagued by reliability and performance problems, Caen is clearly fed up with it, and has launched a project to convert to a standard LRT tramway — running on bona fide tracks — by 2019.
In France, the designation TVR, Transport sur Voie Réservée, roughly translated as “transport on reserved way”, is used to refer to these rubber-tired guided-bus systems. In English, they’re often referred to as GLT, for Guided Light Transport. As explained in a Wikipedia article, “GLT vehicles bear a strong resemblance to trams, but are actually buses capable of following a single guidance rail or even operating without any surface guidance system.”
Opened in 2002, Caen’s guided-bus system eventually stretched to 15.7 km (9.8 miles), using longer-than-usual articulated buses guided by a flanged wheel running on a center guiderail in the middle of the paveway. While the buses have diesel motors (and steering wheels, so they can be driven to their garage at night), their ordinary propulsion is electric power, via an overhead contact system (OCS) and LRT-like pantographs, with the guiderail also serving as the electrical return circuit. (The dual rails of standard LRT serve this same purpose.)
However, reliability problems with the technology (especially derailments of the guidewheels) reportedly have persuaded Caen’s political leadership and transit management to ditch the guided-bus system. In the new LRT tramway plan (see graphic simulation at top of post), 16.8 km (10.4 miles) of LRT routes will replace (and slightly extend) the guided-bus routes, and tracks will replace the paveways (or be embedded in some sections of pavement). A fleet of 23 trams is projected to replace the BRT buses, with a total project cost estimated at €247 million (currently about $269 million, or about $26 million per mile). Project completion is aimed for 2019.
From its early years, the usefulness of the system, as a substitute for standard LRT, baffled transit advocates and professionals. As John Carlson, one advocate posting to the Eurotrams list in 2004, commented
I found the system at Caen and also the one at Nancy to be a solution in search of [a] problem. While there must be some economies from installing just a guide rail instead of double-railed load bearing track looking at the system in [situ] I would have to ask if the guide rail is needed at all.
The vehicles are long and do turn some sharp corners but I’m still not sure if they would be beyond a competent driver and a well-constructed articulated bus operating without a guide rail.
As time went on, other problems, such as pavement wear, began to emerge. Graeme Bennett, a transit advocate in Melbourne, posted observations about the Caen system in the summer of 2005:
A friend and I recently visited Caen and were shocked, stunned, and amazed as we watched and rode these weird vehicles.
We found they were speedy, but fairly noisy, and seemed to do the job well, although they rode more like a trolleybus rather that a tram, in particular with a lot of vertical perambulations and rear end whip as they rounded corners at speed!!
One point that was obvious is the fact that because the vehicles follow exactly the same part of the road without any deviation for cut in or out, … the road surface in some areas is becoming badly damaged particularly at some of the stops where it was noted repairs have had to be made.
Even the smallest pothole will deteriorate rapidly and every tyre on every bus will hit that spot in exactly at the same place every ten minutes or so.
Bennett also observed what seemed to be an emerging problem in keeping the guidewheels in contact with the center guiderail, reporting that “We noted several “Rerailers” around the system to direct the guides onto the track.”
By 2009, serious problems with derailments were being experienced. At the end of May that year UK transit advocate Simon P. Smiler reported that, days earlier, “there was another derailment in Caen, and now it seems that their TVR rubber tyred ‘trams’ are only providing a part time service.”
Smiler wondered “Will this result in the ultimate death of the TVR as a mode of transport? Caen was looking to getting more TVR’s to expand its system — so what will it do now?”
Caen’s experience re-opens anew some of the considerations we originally raised 15 years ago in our LightRailNow.org article prompted by the very similar new guided-bus system in Nancy (also plagued with guidance reliability problems): «“Misguided Bus”? Nancy’s BRT Debacle Exposes Pitfalls of “Half-Price Tramway”». Asking “Does the ‘guided bus’ really have a purpose in life?” our article pointed out that
They basically will have a system of elongated trolleybuses camouflaged as “trams”, with lots of gadgetry to keep the buses on course. They will have a central slot to deal with in the middle of the paveway (tending to collect rain, mud, etc.). And they will be persistently trying to solve lots of operational challenges over the next months and years to prove the whole thing works. Thus one can safely predict that Nancy will be expending a lot of its planning and administrative energy trying to solve the challenges of making a trolleybus system mimic the performance of an LRT system.
There’s a recurring question: Why bother at all with the guide rail in the slot? it is dubious whether such an arrangement will permit higher vehicle speeds, although Nancy designers seem to think their bus will run a bit faster in a narrow right-of-way if it’s guided in this fashion. One is tempted to suspect that the extra-long, multi-articulated bus benefits from having its axles guided by such a mechanism, possibly minimizing any misalignment of the rear section while in the guideway (which might explain why the vehicle tends to “fishtail” when free-running).
And beyond the question of whether it’s worthwhile trying to imbue a bus with LRT characteristics, there’s another issue as well. Once a transit agency or government entity buys into an entire, specific “guided-bus” technology, its planners and decisionmakers commit to a specialized guideway and technical infrastructure using one form or another of specially designed curbs, below-pavement conduits, special travel lane markings, etc. That might happen after the initial order of vehicles, where competition is alive and well, and the initial bidding environment may be fairly competitive among a number of vendors.
However, the agency then has a stock of specialized buses with a 12 or 15-year life expectancy and capital costs sunk into building a specialized guideway which may work properly with only one manufacturer’s product. When the agency proceeds to expand the fleet or must find replacement buses, it may well find itself “trapped” with only one manufacturer/bidder. Is any vendor going to assure transit planners that its proprietary technology will become an industry standard in the next dozen years? …
In contrast, imagine instead that the transit agency set down a few miles of steel rails with 1435 mm (standard) track gauge with readily available, dependable track switches, and mature signalling technology. The agency buys a couple of dozen light rail vehicles which have a lifespan of 30 to 50 years with trainlined controls so that one operator can control two to four cars. When it’s necessary to expand that system or replace the vehicles, the agency will find at least half a dozen suppliers lined up who can make cars which will work fine with the previous generation. Productivity is better, competition is alive and well, and the technology is mature.
Certainly, in view of recent experience, those comments seem as relevant today as they were a decade and a half ago. ■