Interesting, obviously the most serious SOL a driver could have is a SPAD I’m assuming. What are the most common SOLs do you know drivers have? And 24 weeks notice is crazy. What 357 said is probably the most efficient way to escape.
A SPAD generally is the worst although even they can vary greatly in severity and many even result in derailments or possibly collisions. TPWS interventions (particularly approaching a red) are serious as are TPWS activations (the difference between the two being that an intervention is where the Driver hasn't braked, an activation is where the Driver is braking but is exceeding the braking curve).
Station stop shorts, Station overruns, Station fail to calls are investigated and recorded.
Any instances of speeding are recorded and if its deemed excessive, are dealt with severely.
Other infringements could potentially be a buffer stop collision, a collision with a train (permissive working or in depots/sidings).
Rule book infringements could be recorded if classed as a SOL incident