Gawnsoft ) gurgled
happily, sounding much like they were saying :

It's more like telling someone a helmet will Save Their Life [tm]

True.

Very similar, also, to saying that religiously sticking to a speed
lower than some arbitrary number on the side of the road is safer than
setting a speed based on the conditions.

Of course these speed limits are not completely arbitrary as you
suggest, but vary depending on the conditions.

No, they don't.

e.g. residential urban street 20mph, rural motorway 70mph

residential urban street at 8.40am in ****ing rain - 30mph
residential urban street at 2.30am, clear and dry - 30mph