Would have been the driver. ATO will only ever restart between stations when stopped at a red signal/block marker board
A slip can be an act of unintentional sliding - so I think so, yes.
When there's poor adhesion in braking the wheels start slipping and if nothing is done, will stop and the wheels will slide. The point if wheelside protection (WSP) is to keep the wheels turning unless the adhesion is terrible. It makes the most of whatever adhesion is available, although stopping distance will be extended. Adding sand tends to improve adhesion, so sanding is triggered by the WSP to help stopping performance.
No, the wheel doesn't lock momentarily. There is significant potential energy in a rotating wheelset, especially if it's connected though a gearbox to a motor. Thus, a braked wheel on low adhesion takes time to stop rotating (i.e. lock) giving tome for the WSP to do its job. "Repeated momentary locking" might have been observed with primitive WSP, but not with modern systems or unless the adhesion is really bad - eg a coefficient of friction in the 0.01-0.02 range.Indeed, but of course the "start slipping" is presumably the wheel repeatedly locking momentarily - it isn't rotating against the railhead, as it would if slipping when under acceleration - the forces are of course the wrong way around for that! E.g. a train may "slip to a stand", when failing to gain traction under acceleration, but would "slide past a signal" etc when under braking.
I'm being pedantic here I realise, but seeing as it was brought up, I would contest that "slip" is essentially wheelspin, and therefore an acceleration issue, while "slide" is a deceleration thing?
I am growing a beard and perfecting my nasal tones as I type....
