TRAMWAY
The modern tramway is a guided transport system which runs ground level (on reserved lanes or in mixed road traffic); in comparison with the traditional tramway, the moder one assures higher commercial speed and higher capacity, thanks to the protection of its lanes (ofen segregated) in order to reduce the road traffic and pedestrians interferences.
The modern tramway track is based generally on standard gauge rails (1435 mm).
Tramway global market has benn characterized, in the last years, by politique of industrial concentrations, that have made emerge (in Europe) four main producers:
Alstom
Ansaldo
Bombardier
Siemens

Each of them tried to razionalize its production (which needed to armonize the different standards got from the assimilated companies) by the development of the so-called "tram standard", a modular kind of vehicle easy to be adapted to the particular requests of each purchaser. The tram standard percentage over the total tram production is currently about 70%.

One of the distinguishing elements between the different models is the floor heigth as far the rails.
Some of the modern tramways (partial low floor) are infact more similar to the traditional ones, with the bogies able to rotate regards the car-body. In the traditional trams floor heigth was up to 900 mm, in the modern partial low floor trams it's about 600 mm over the bogies, while it's only 350 mm in the rest of the vehicle.
A more innovative concept characterizes the full low floor trams, which floor is about 350 mm in every part of the car; this result has been possible thanks to the adoption of particolar bogies fixed to the carbody; the insertion of the vehicle in the curves is obtained thanks to some of the cars which are suspended between two cars on bogies.
Partial low floor trams maximize the cinematic performance and the cars durability, while full low floor trams assure a whole easy approachability in every part of the vehicle.

Every model offers the double option of the mono and bi-directional type; the latter are more flexible as far the track design (central and side platforms stops are both possible) but they must renounce at some seats in both side of the doors.

As said before, modern tramways generally adopts standard gauge rails (1435 mm), even if some variations (like the metric gauge) are not infrequent, when required by the purchaser.


Links to the producers sites:
ALSTOM
ANSALDO
BOMBARDIER
CAF
SIEMENS
SKODA