Breaking Distance,reaction time,visibility

 Factors affecting breaking distance:-(priority wise)

1. Train speed

2. Train Load

3. Gradient 

4. Brake power

5. Types of brakes

6. Condition of Rail

7. Rail/wheel adhesan 

Service Breaking Distance (SBD)

The drivers are normally supposed to apply brakes gradually, so that breaking may not cause discomfort to passengers. The breaking distance obtained with gradual application of brakes is called SBD or Normal Breaking Distance (NBD).

Emergency Breaking Distance (EBD)

When brakes are applied suddenly, the breaking distance required would be less but the rate of declaration may cause discomfort to passengers and in case of freight trains,may damage the consignments.The breaking distance with sudden appliance of brake is called EBD.

SBD is 1.2 times EBD

The inter signal distance is always based on Emergency Breaking Distance (EBD)


Reaction time 

When driver approaches and observes a signal, he can not be expected to instantaneously react to the aspect of signal, but after some time. This time is called Reaction time.

When driver is in process of reacting to the Aspect of a signal, the Train is running at max speed and distance covered during this Reaction time is called Reaction distance (RD).

Reaction distance on Indian Railway is 200 m

Reaction distance plays a crucial role while determining the minimum visibility required for a signal.

Visibility of the Signal IRSEM- 7.1.11

All Stop Signals -200 meters except Distant.

Inner Distant- 200 m

For Distant -400 m

Where it is not possible to obtain 200 m of continuous Visibility of any stop signal ( due to site constraints), then suitable speed restrictions shall be imposed.



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