I believe GP equates "safer" with "no hobos, gangstas, creeps, drunkards or other people creating a nuisance for fellow travellers", and he is absolutely correct on this.

Public transport has the downside of being public, and given the rise of homelessness and the fall of noncommercial venues where e.g. youth can hang around, it's inevitable that they end up in public transport - and create a feeling of unsafeness for other users.