Leadsled
What I also remember was that the ARB factors were smaller than CAB/FAA figures, and the bottom line was that the final figures wound up being very similar
For our aeroplane(s) the ARB distances always came out a bit higher than the factored FAA distance, which was a marketing disadvantage so we ended up doing both if we wanted certification in other than the UK.
But the FAA couldn't have been altogether happy with their distances or they wouldn't have gone to all the expense of their DBV programme I think?
Which, since they never changed anything, prompts a question as to why? Possibly better brakes and more reliable reverse thrust have given better statistics (and yes I know you can only get credit for that if you can show it to be reliable - but that is for certification distances not the reality of everyday operations).
OTOH aircraft still go off the runways from time to time so it can't be all sweetness and light ...........
Cheers