Breaking Distance:

The distance traveled by train after its brakes are applied is known as Braking distance.There are two methods of Application of Brakes

  1. Normal Service application
  2. Emergent application including setting in reverse.
Braking distance depends on :
  • Speed
  • Brake power available
  • Gradient
  • Rollability of wheels
  • State of rails, turbulence of track
  • Wind velocity, weather condition (dry or wet)
  • Type of train
  • Load of train
  • After all tests, it is now decided that for a full load passenger train on the level of the gradient at 65 kmph, the braking distance is 1 km approximately.

The distance over which the most restrictive aspect of a signal is visible from the driving compartment of an approaching train under normal condition of visibility.


It is the distance traveled at the permissible speed during the time taken by the driver to react to the aspect of signals.

Minimum Sighting Distance = NBD + RD

Sighting distance is an uncertain factor – In two aspect signaling – signals are not pre-warned.In multiple aspects, all signals are pre-warned by aspects of signals in advance.

  • Outer – 1200 Mts. Where section speed is 100 kmph and above Warner : (on independent post) – 400 Mts.
  • Home – 400 Mts.
  • Main Starter – 400 Mts.
  • All other Signals – 200 Mts.
  • Distant – 400 Mts. Inner distant – 200 Mts.All stop signals – 200 Mts.
  • Where not possible to have continuous visibility as above, the speed of trains is to be suitably restricted.

Signals are normally located on to the left side of the track. However, for better visibility, a signal may be located on the right side also.

Two Aspect Homes :

Should be located close to the first set of facing points clear of the lock bar. If it is necessary to increase the distance between the Home and Facing points beyond 180 Mts. Other arrangements should be made for holding the route.

Multi-Aspect Homes :

Should be located at 300 Mts. Is (180 + 120 Mts.) from the first facing points. Facility for shunting in face of approaching if provided, the home may be shifted outward. So that block overlap is available between the home and opposing advance starter or shunting limit board. On double line, Home may be located at 180 Mts. in the rear of facing point or Block section limit board.

Starter Signals :

Should be located at the leaving end fouling marks or lines in the case of parallel lines at distance exceeding train length from the signal in the rear. The distance between the homes and starting should not be less than 400 Mts. In the case of LQ signaling and 180 Mts. in case of Multi-aspect Signaling. An alternative location is a signal overlap in the rear of fouling mark. This provides more operational advantages.

Advanced Starter :

On single line at 180 Mts. from the Outer most trailing point. The distance may be increased if required, provided the opposing outer in ‘B’ class station, the home in MAUQ as the case may be can be located at a distance of at least block overlap from the advanced Starter.

On double line, it should be placed at full train length plus signal overlap in advance in Starter signals. But in the present practice, the advance starter signals are being located at 120 Mts. from Outer most trailing points.