What is the advantage / reason for many trams being high floored and non-accessible?
- By
- Aparna Patel
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- 22 Jul, 2023
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The general answer is, because rail-borne rolling stock is expensive, it is only rational to expect trams to have a long life cycle. It is not unusual to see trams which are 30 years old, and in some places you can meet trams built in something like the 1930s and still in use.
Thus, because low-floor tram designs are relatively new (introduced in 1980s and only ripened in 2000s), the share of high-floor trams must necessarily be sufficiently high still, even in the most advanced cities.
However, some tramway systems have features that make it impossible to use low-floor cars. For example, San Francisco’s Muni Metro or Düsseldorf’s Stadbahn have underground stretches where stations have high platforms. Unless those stations are rebuilt (which may be prohibitively expensive), they are bound to use high-floor cars.
There may also be less obvious reasons to use high-floor trams.
We might go into further specific details if you tell us about which particular cities made you ask your question.
Update:
The particular cities named were Budapest and Melbourne.
Both cities have very extensive tram networks (Melbourne’s is the largest in the world). Their fleets are numbered in hundreds of cars and can only be replaced gradually.
Budapest, as far as I know, has not been showing a quick progress in this matter because most of their money went into the construction of a new metro line.
There are no special features impeding the use of low-floor trams that I ever heard of.
From an engineering point of view, a tram is a vehicle that takes electricity from somewhere (overhead wires or third rail underneath), use motors to convert this into torque, and spins wheels to move the tram. The obvious solution is put all this machinery at ground level, right next to the wheels, and put the passengers on top. Ta-dah, a high-floor tram.
If, on the other hand, you want a low-floor tram, you’ve got to figure out some way to hide this machinery somewhere else, so passengers can use the space near the ground, but still feed the power to the wheels. This is tricky and expensive, plus the tram can get top-heavy and unstable if you stack everything on top. One mitigation is to fix some of the wheels in place, so they require less space, but then the turning radius of the tram also becomes larger, because the wheels can’t turn sideways.
That said, this is largely considered a solved problem these days, so virtually all new trams are low-floor. However, trams are expensive and last decades, so replacing old rolling stock takes a good long time. And if you’ve attacked the problem from a different angle and built elevated stops to make high-floor trams accessible, the same high stop is no longer compatible with low-floor trams!
Cost, and speed.
Some public transport companies report that low floor trams have 15% higher maintenance costs for the rolling stock, and 20% higher maintenance costs for the infrastructure on average (source in German).
The low-floor designs typically also decrease the speed at which a tram can drive through a curve (usually 4–15 km/h in 20 m radius curve)
There’s also quite a good article on Wiki about Low-floor trams.
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