I am a long time lurker on pprune and would never dream about commenting about anything that I have no knowledge about. I am a train driver in the UK and we have a drug and alcohol policy which is based on the Transport and Works Act 1992. For alcohol we are allowed nothing in the 8 hours before signing on. From 24 hours before signing on until the 8 hour cutoff you are allowed to have 7 units of alcohol. A pint of 4% lager is 2.3 units. All medication including over the counter must be declared and if there is any doubt it has to be cleared by occupational health department.