Rail adhesion

In the railway sector is referred to as adhesion railway (also friction track ) when the drive is alone on the static friction of the wheels. In railways, liability or adhesion between railway vehicle wheels and the rails of the infrastructure is low, so there is little friction losses occur, but can not be overcome steep inclines without aids as for rack railways or funiculars.

Be problematic not only the limitation of static friction traction at high loads, but also the addition downhill acting friction forces and gravity component turns when driving uphill and braking on the downhill. In the friction limit is exceeded, the wheel goes on the plane. By sanding the track of the work area can be increased by wetness decreases the working range of static friction.

Main lines are usually built with a slope of up to 30 ‰. Over shorter distances, higher gradients are possible, such as 135 ‰ for the tram in Lisbon. As steepest adhesion on a longer route is considered the Pöstlingbergbahn in Linz, which is applied to almost the entire route with a slope of 105 ‰, in particular, there is a continuous stretch of 1315 m length with gradient 105 ‰. As steepest standard gauge adhesion railway in Europe with 85 ‰ applies the southern branch of the line U15 Stadtbahn Stuttgart; before the conversion of this former tram line to standard gauge was the Uetliberg in Zurich record holder with 79 ‰. The 60 km long Bernina Railway, the altitude of 2,253 m. M. rising, has a maximum slope of 70 ‰ and is regarded as the highest adhesion railway in the Alps.

Main lines with a slope of more than 25 ‰ and branch lines with a slope of more than 40 ‰ are in Germany a steep section.