DVD and DSD in cab safety devices

[Ditop23]

I'm trying to differentiate between these 2 safety devices and their operations.

DSD
You drive with your foot on the peddle. A beep will alert you every 60 seconds. You then lift and re apply the pedal.

But what is, and how does the DVD work.

Thanks

 

[SiTheTrainGuy]

They are sort of one and the same thing.

DSD is the pedal you need to press down when in forward or reverse. Without doing this the train goes nowhere. If left off long enough then it alerts the signaller.

DVD (Vigilance) is the 60 second timer you refer to after no other driving inputs power/brake, horn (in certain trains).

All trains have DSD, not all have Vigilance although most newer trains do.

 

[Harpo]

DSD is the pedal you need to press down when in forward or reverse.

In original format pre-1980s DSD could be bypassed in EO (engine only). After a runaway incident (Carlisle??) a speed sensing switch (SSD) was added which needed the DSD to be held down at all times when moving.

 

[Efini92]

In original format pre-1980s DSD could be bypassed in EO (engine only). After a runaway incident (Carlisle??) a speed sensing switch (SSD) was added which needed the DSD to be held down at all times when moving.

it also had to have the master switch in forward or reverse. If it was still in engine only at 6mph it would apply the brakes.

 

[Harpo]

it also had to have the master switch in forward or reverse. If it was still in engine only at 6mph it would apply the brakes.

No. That only came about with the SSD mod. Prior to that, EO was used to coast at speed.

 

[Stigy]

The DSD is the mechanical device which requires driver input, where as the DVD is the device which operates the timed warning and will put the brakes in if it’s not responded to.

I guess the DVD does all of the work really, since the DSD is essentially just a switch?

 

[Efini92]

No. That only came about with the SSD mod. Prior to that, EO was used to coast at speed.

Oh really? Before my time that. Switching to engine only would dump the brakes.

 

[InkyScrolls]

For example, a 155 has DSD but no DVD. If you get out to check your lights with the direction selector in forward, after 9 secs the brakes will only. After a further 30 secs an alarm will sound in the cab. After 30 further seconds the signalman will be contacted. So on a 155 it's especially important to check the DS before leaving the cab, as there's no DVD to warn you!

 

[D365]

In original format pre-1980s DSD could be bypassed in EO (engine only). After a runaway incident (Carlisle??) a speed sensing switch (SSD) was added which needed the DSD to be held down at all times when moving.

SSF is the speed switch that British Rail implemented in the 80s. Not sure what it stands for though.

 

[Efini92]

SSF is the speed switch that British Rail implemented in the 80s. Not sure what it stands for though.

Slow speed fitted for the merry go rounds?

 

[D365]

Slow speed fitted for the merry go rounds?

No - that’s slow speed control. SSF is the DSD speed switch that was retrofitted by British Rail.

The DSD is the mechanical device which requires driver input, where as the DVD is the device which operates the timed warning and will put the brakes in if it’s not responded to.

I guess the DVD does all of the work really, since the DSD is essentially just a switch?

Not quite. All vehicles with DSD require the footpedal to be continually depressed. What vigilance does is add the timer to ensure the driver releases and reapplies the footpedal at regular (~60 second) intervals if no other driver activity is detected by the vigilance device.

 

[Harpo]

SSF is the speed switch that British Rail implemented in the 80s. Not sure what it stands for though.

I just recall it was ‘Speed Sensing (something).’

As locos got modified the fitment was announced with a ‘SS(something) FITTED’ sign in the cab above the windscreen, good enough warning not to go into EO after powering off as you’d dump the brake.