Without any doubt whatsoever, the worst ever bus I travelled on has to be BZY 821 in 1983. This was owned by Crossons in Drogheda at the time, and it was a former British Ministry of Defence Bedford VAM dating from 1967. It was being used on the day in question on a run from Drogheda to the AnCO (now FAS) centre in Dundalk, and it was a winters day -- yet the driver insisted on driving along with the doors open!!

It was only after a few complaints of coldness that he closed them -- only for us passengers to find that the bus very quickly started to fill with fumes from the engine........