Helen Deborah Vecht wrote:

I think the only thing that would stop graffitti / etching /seat
slashing is the presence of enough staff to prevent such actions. This
is expensive.

So is replacing windows. The economics are not as clear-cut as the
operators might like to believe.

If the rate of window scratching were as much as one window per bus
per day, preventing it would probably pay for an extra employee shift
per bus per day.

Colin McKenzie