2. Basic wheel technology – rail

The guiding and rolling of two flanged wheels on two beams called "rails" is the basis of the railway system, whatever the traction energy. This technology has two essential properties:

• load distribution on the floor ;

• guidance of all vehicles combined to form a train.

A derivative of this technology uses a rolling tire combined with lateral guide wheels, and is used in heavy urban transport, such as the metro (figure 2 ).

It should be noted that the pneumatic wheels are combined with conventional flanged wheels, and the track has two lines...