This series charts the specialities, differing best uses, and newer developments of different local rail systems. This part covers light rail.
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Yarra Trams class C tram No. 3008 (low-floor type Citadis 202 of French maker Alstom) in Melbourne; January 24th, 2003. Photo by Stuart Jackson from Perthtrains |
This series can also be viewed as a general guide as to what kind of projects local initiatives could aim for, and tries to give examples around the world that can be used as model for supporters and argument against opponents.
Some general points are valid throughout the series.
Don't think in lines, think in networks -- even if a first line won't grow into a full network in decades. Coordination between different modes of transport, rather than rivalry, is essential. Even just in rail, one shoe doesn't fit them all. Different public transport modes are for differing kinds of travel, and it's best to have them as different levels in a linked-up system, say:
- high-speed rail,
- express rail,
- normal stopping trains,
- rapid transit,
- metro (subway/elevated),
- light rail,
- buses.
Of these, this series covers the four categories of local rail (nos. 3-6 on the list); as well as some ingenious ideas to mix these categories.
This series was inspired by BruceMcF's diary on various local transport modes as potential 'recruiters' for high-speed rail. Jerome a Paris was kind enough to guest-post Part 1 (on 'normal' stopping trains), I posted Part 2 and Part 3. Meanwhile, BruceMcF wrote parallel diaries emphasizing connections to high-speed rail and that buses and trains should be friends, and The Overhead Wire wrote about Transit-Oriented Development.
Light rail/Tram/Trolley/Streetcar
In a city, one may also opt for street-level transport, gaining easier access at the price of lower speed: you have to wait at cross-streets. This idea was first tried in the USA: in New York in 1832. But it really took off in the last two decades of the 19th century, after Werner von Siemens invented electric trains: lack of air pollution and good acceleration were the decisive factors.
The new transport mode, variously called tram, streetcar, and trolley, had some specialities forced on it by streets: rolling gear and body made so that tight curves can be negotiated, cars are narrow, entrances are for practically rail-level boarding, not too high speeds allow catenary on the cheap, and special rails are sunk in the pavements. Also, with no need to be strong enough for long trains, cars could be built lighter, hence the modern name light rail.
Trams evolved for half a century (which I documented with examples from my hometown Budapest/Hungary), but then got stuck. In the USA, the PCC made the revolutionary switch from single axle rolling gear to bogies (which give a smoother ride) in the thirties, but still from the next decade, nothing held up the clearcutting of streetcar lines to make way for buses and cars. Funnily, starting from a PCC license, Czech maker ČKD became the world's biggest tram supplier during the time of the more public transport friendly East Bloc, Tatra tram parts were then even used in New Orleans. Western Europe got as far as articulated trams in the fifties, but then the big cull started there, too, and the surviving systems seemed struck in that age.
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All-weather service: a type T5C5K at Moszkva tér in Budapest, a Tatra built in the eighties. February 13th, 2004. Photo by Ákos Varga from RailFanEurope.net |
That there is now an on-going light rail revival had reasons in technology. The following appeared in trams from the seventies, many of which later found their way into normal trains:
- AC motors: beyond being lighter and stronger than DC motors, they provide continuous acceleration (thus no jerks due to switching between speeds), and by using the motors as generators, they can function as brakes;
- disc brakes;
- rubber and air springs, dampers: smooth ride instead of the classic rumbling;
- air conditioning;
- new automated door mechanisms: you can make entrances that can adapt to platforms of different height.
All these technologies were successfully merged for the vehicles of the Stadtbahn systems in West Germany (covered in the next episode), and also in Japan. There was an attempt in the Oil-Crises-era US too, but, unfortunately, the Boeing-Vetrol-developed US Standard Light Rail Vehicle was plagued by construction problems, so US light rail systems now rely on imports.
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Stylish low-floor trams in Strasbourg (three types: the 7-part/33.1 m and 9-part/43 m versions of the ABB [now Bombardier] EUROTRAM used since the 1994 opening, new 7-part/45.056 m [147.8 ft] Alstom Citadis 403 (2005)), January 2007. Video by YouTube user Roberto Amori |
The light rail revival really took off in the nineties, thanks to another innovation spurt in France:
- size reduction made low-floor trams possible, with most of the electric equipment on the roof;
- lightweight alloys could be used for lighter carbodies (though some manufacturers had big problems with these);
- departing from bland industrial designs, trams with more stylish and aerodynamic fronts made trams hip (see Strasbourg video).
Sometimes politicians treat light rail as if it were an alternative to subways or rapid transit, a cheaper alternative, but that is a bad idea to have. The busiest light rail line in the world, the one along the Grand Boulevard in my hometown Budapest, has a weekday ridership in excess of 200,000, but it is constantly crowded and relatively slow despite extra-long trams every 2-4 minutes.
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Giant caterpillar: tram No. 2008 (Siemens type Combino Supra) on the Grand Boulevard in Budapest, in front of West Terminus railway station. With a length of 53.99 m (177'1½"), they are only surpassed by Dresden's CarGoTram. My own photo of July 5th, 2007 |
Light rail is the right choice for ten to hundred thousand daily trips, not higher (or lower). With that, it could serve as the backbone of public transport in cities between 100,000 and 3-500,000 inhabitants. Above that, it is best used as feeder/distributor for heavier rail systems. For example, should the (already well-frequented) METRORail in multi-million city Houston expand from a single line to a real city-wide system, and induce a large proportion of inhabitants to switch to public transport, the addition of a proper subway or express railway would become unavoidable.
In major cities, light rail can be especially useful as further-from-the-centre orbital service: traffic volume is usually much less than on radial lines, but most people would need to travel that way at least sometimes. London, Paris, Madrid have/are building such lines. One has been proposed for the US capital too, the Purple Line, to alleviate the one big problem of the otherwise mostly fine DC Metro.
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Map of the current tram network of Budapest (yellow/red), with subway (dark grey, dashed: in construction) and local and commuter rail (thick resp. thin light grey) also drawn in. Note the five concentric partial orbital lines on the East bank of the Danube. Based on map on Villamosok.Hu |
As light rail is street-level, it must also be coordinated with road traffic. Special attention must be given to this in cities where generations grew up without knowing railways. People must be taught that even the lightest light rail is much stronger structurally than a car -- and has a longer braking distance. That is, unless traffic lights are green for you and red for it, rail has traffic priority, always. You need new traffic lights and extensive information campaigns for car drivers to avoid frequent incidents, like during the first few years on Houston's METRORail.
Since light rail can determine cityscape, projects can become prestige objects, with municipalities accepting higher costs. The latter can result from senseless spending on glitch, but also from well thought-through planning, especially in France. For example, while line extensions in Germany cost as little as 10 million €/km (22 million $/mi), Houston's METRORail 43 million $/mi, and Minneapolis's Hiawatha Line (which has a tunnel section!) 60 million $/mi; Paris's 7-moth-old T3 line comes in at around $87 million per mile.
But benefits like commercial development in a more attractive area with more greenery, traffic also reduced by taking 1-1 lanes away from a busy road, while the 304-place trams provide twice the capacity of the earlier bus line at a 38% higher travel speed, made it worth, with extensions underway. And even with such high-cost, high-quality light rail projects, French cities manage to simultaneously expand their bus services (for example Strasbourg).
I close this with two technology innovations from France. The first is light rail without catenary (overhead wire). Bordeaux's new light rail line has a segmented third rail in the middle, whose segments are put on voltage with a radio signal only when a tram is above. Attempts at ground-level power supply have a 120-year history, but after heavy teething problems, this one seems to work.
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High-tech, style, low-floor comfort in one: a Bordeaux tram (an Alstom type Citadis302) on a catenary-free section at Quai Richelieu, August 16th, 2004. Photo by P.Chapar from RailFanEurope.net |
The second innovation demands a category of its own.
Tram-bus
Electric buses (trolley-buses) have the carbody of buses, but transformers and inverters in place of the diesel. They are bound to certain streets by poles having to reach overhead wires, but drive normally on streets. They can get their own special lane, though, and special guiding tracks or fixed route markers an automated system could keep the vehicles to. What they won't have is light rail capacity (whatever US Bus Rapid Transit advocates claim).
Now what if we start with a tram, put rubber tyres on its wheels, and replace its two riding rails with guiding rails? Is that a trolley-bus? Well, it has pantograph rather than poles, has a different and larger carbody, is fixed guideway, and operates just like light rail, though these differences might get further diluted in the future, if a new niche is found. But the only obvious benefit over normal light rail I can see at the moment is not cost, certainly not ride quality, but the ability to climb higher grades.
The described 'off-rail light rail' of French company Lohr Industries was pioneered with a test track in Paris, there are a few applications elsewhere so far.
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Translohr vehicle No. 004 on Binhai Mass Transit's guided-rail, which serves Tianjin Economic Technological Development Area (TEDA) near Tianjin, China since May this year. Photo by Pierre2427 from 2427junction.com |
Another rubber-tyred system will be described in the next episode.
Outlook
The next part will cover newer mixed-mode systems based on light rail: light metros and tram-trains. As the concluding part (to be posted Tuesday, probably by Jerome a Paris), it will also conclude with a view on overall public transport development strategy.