sentences:  Other causes include the contact of oil with the flanges and rims of wheels, which reduces adhesion with the surface of the rails, and a general loss of traction on steep gradients when pulling heavy loads.Most locomotives are fitted with sandboxes, so that sand or Sandite can be dropped on the rails to improve adhesion.Modern diesel locomotives and electric locomotives are fitted with electronic wheelspin detectors which automatically reduce the power supplied to the wheels if wheelspin is detected.