Mm. Interesting reading the links but I think there’s a distinction worth remembering. It does seem there’s been civil cases bought forward by claimants holding their employers liable for personal damages.
To stay on track, keeping it simple and, for the purposes of the question the OP asked. I still think think it worth re emphasising the law lot hold a driver responsible. So work outwards from there.
For instance quite common for a fatal RTC for at least one driver to be quickly arrested on suspicion. Work from there and keep yourself right.
I see it unlikely you’d escape some sort of legal attention if you caused a crash by nodding off or were reported for the offence of driving without due care and attention. Of course, the employer could perhaps also be persued by the authorities but you’d have to be whistling a pretty good tune for your employer to cop full responsibility for driving offences.
The dual persueing is perhaps more common in companies associated with road transport such as hauliers and coach firms holding O licences. The DVSA and Police are particularly energetic at perusing companies in that regard alongside their drivers.