Am seeing both sides to this.
The problem here is that the railway authorities treat all types of incidents as "safety of the line" (SOL) incidents, irrespective of the outcome. We've had these arguments many many times in various messrooms that a failure-to-call (FTC) has not compromised safety, so how come it's classified as an SOL incident? Well it just is, as a colleague of mine discovered.
As such, if you have any sort of SOL incident the management response is likely to be the same whether it's an FTC, station overrun or a SPAD. You are likely to be relieved of duty, possibly medscreened for intoxicants (a definite in the case of a SPAD) and interviewed by management to try and understand the causes and factors that lead up to the SOL incident. You may be off the road for a few days and will almost certainly have some manner of action plan to help you avoid a repeat of the mistake. So in that sense, an overrun is treated in exactly the same way as a SPAD.
The other thing is that these sorts of "lesser" SOL incidents are often precursors to something more serious. A DM once told me that the stats show that drivers with more than one FTC or overrun are at much higher risk of going on to have a SPAD than those with one or fewer. These other SOL incidents could be indicators of poor cab discipline, bad driving habits or a lack of concentration. Even routine monitoring using OTMR downloads have shown where poor driving technique has almost resulted in an SOL incident or shown up a particularly high-risk behaviour. Using all these indicators can help management to identify those drivers most at risk of having an SOL incident and to help them avoid having them.
**EDIT**
You can indeed claim that a contributory factor in an SOL incident is poor brakes or a faulty speedo, but the effectiveness of doing so is questionable. If you overran your very first station stop then there might be a case, but if you're on your third round trip on the same unit and then you suddenly slide through one it might not be quite so effective. Likewise, you don't get very far before carrying out a running brake test which should highlight that the train has a poor brake and you would modify your driving style accordingly to allow for it.
Faulty speedos can be a bit harder to diagnose, but not massively so. If a train seems to take an age to reach linespeed and then you arrive at the next place early after nearly overrunning the platform, then there's a good chance it's the speedo. Maybe it's just me, but I've got a pretty good nose for these things and can usually identify them within a couple of station stops. However, in common with poor brakes, these are the kinds of things that drivers will report and, if the train is to stay in service, will advise their relief of.
But the real test will be what the OTMR says about the brake, which goes back to the first point in my edit. You would need to be pretty certain of yourself if you were going to try and use poor brakes as a mitigating factor, because if the OTMR shows you were perfectly fine on the brake leading up to the incident and then demonstrated poor technique or a late brake application they won't be inclined to pull the unit for inspection.
Either way, if the train was faulty in some way that contributed to the SOL incident the driver would almost certainly still have had to wear at least part of the blame.
O L Leigh