Adhesion sheet
In the railway sector , one speaks of an adhesion track (also friction track ) when the drive is solely via the static friction of the wheels . In the case of railways , the friction or adhesion between the railroad wheels of the vehicle and the rails of the guideway is low. There are only few frictional losses . For steep inclines, aids such as rack railways or funiculars are required to avoid sliding. Otherwise large differences in altitude could not be overcome.
Not only the limitation of the static friction in traction of high loads proves to be problematic, but also the addition of frictional forces acting downhill and the gravity components when driving uphill and when braking on the downhill drive. If the friction limit is exceeded, the wheel begins to slide. The work area can be enlarged by sanding the track, while wetness reduces the work area of static friction.
Main lines are usually built with a gradient of up to 30 ‰ . Higher gradients are possible on short stretches, for example 135 ‰ on the tram in Lisbon . The steepest adhesion railway on a longer route is the Pöstlingbergbahn in Linz , which is laid out with a gradient of 105 ‰ for almost the entire route, in particular there is a continuous section of 1315 m in length with a gradient of 105 ‰. The maximum gradient is 116 ‰ on Hohen Damm . The steepest standard gauge adhesion railway in Europe with 85 ‰ is the south branch of the U15 line of the Stuttgart Stadtbahn ; Before the conversion of this former tram line to standard gauge, the Uetlibergbahn in Zurich held the record with 79 ‰. The 60 km long Bernina Railway , which is 2253 m above sea level. M. rises, has a maximum gradient of 70 ‰ and is considered the highest adhesion railway in the Alps.
Main lines with a gradient of more than 25 ‰ and secondary lines with a gradient of more than 40 ‰ are considered steep sections in Germany .