Low floor tram

Low-floor tram configurations

Trams traditionally had high floors, and these designs evolved into the tram with a low-floor centre section. Examples of this design are Amsterdam 11g/12g-trams and the Kusttrams in Belgium.

The most common design of 100% low floor vehicles uses short carbody sections for the wheels and longer suspended sections. Examples of this are the Citadis and Combino. A similar, but somewhat older technique is one that has been developed by MAN. In 1990, it was the first 100% low floor tram. These trams are found in ten German cities (such as Bremen and Munich) and in the Swedish city Norrköping. In many other German cities there are trams with low floor between the outer bogies and single axle bogies under the centre section.

"Light rail" type vehicles frequently have a similar configuration but with a centre bogie designed to accommodate a low floor situated under a short centre section. A more radical approach has been adopted for the City Class LRV (Citytram), where the main low floor section is only 300 mm above the rail. The low floor runs right through the articulation of both the 29 m long and 38 m Super Citytram version. In both, the corridor through the articulation is wide enough for seated passengers and a wheelchair to pass through. The City Class has been designed to turn on 15 m radius curves and to climb 10% gradients.

In Austria, the Porsche designed Ultra Low Floor (ULF) Trams can "kneel" at the curbside, reducing the height from the road to only 180 mm.

Some public transport companies have both low floor and high floor trams. They report that low floor trams have 15% higher maintenance costs for the rolling stock, and 20% higher maintenance costs for the infrastructure on average. Among the problems observed is that the missing bogies result in a higher level of wear and tear.

Many low floor trams have fixed bogies which increase track wear and tear, while decreasing the speed at which a tram can drive through a curve (usually 4–15 km/h in 20 m radius curve). The Škoda ForCity and the newest Alstom Citadis X04 try to counter the effect with low floor pivoting bogies while maintaining 100% low floor design. Prior to the new design, pivoting bogies could only be used under high floors, hence such trams could only be part low-floor, with high-floor sections over the pivoting bogies.

Historic examples

The idea of a low-floor tram dates back to the early 20th century when a number of trolley systems began experimenting with various "stepless" designs. Perhaps the most notable is the Hedley-Doyle Stepless car introduced in 1912 for use on Broadway in Manhattan. A number of other cities also purchased Hedley-Doyle Stepless trams after seeing their success in Manhattan. Since these cars had a unique appearance compared to any other trams running at the time, they earned a number of nicknames, including hobble skirt cars, public welfare cars, and sow bellies.

Typical floor heights

To put things into perspective, here are some typical floor heights for public transport vehicles, old and new:

Belarus

Canada

Croatia

Czech Republic

France

Germany

Italy

Japan

Poland

Ukraine

Spain

Switzerland

Russian Federation

Other trams