Contrary to popular belief, riding a bike whilst intoxicated is illegal.
However, there is no set limit like there is for driving. Recently the Scottish Government reduced the level from 35 micrograms of alcohol per 100 millilitres of breath to 22 micrograms of alcohol per 100 millilitres of breath.These strict alcohol limits for drivers do not apply to cyclists but The Road Traffic Act 1988, section 30 states;
30. Cycling when under influence of drink or drugs
(1) A person who, when riding a cycle on a road or other public place, is unfit to ride through drink or drugs (that is to say, is under the influence of drink or a drug to such an extent as to be incapable of having proper control of the cycle) is guilty of an offence.
(2) In Scotland, a constable may arrest without warrant a person committing an offence under this section
Various studies have found that inebriated cyclists are much more likely than sober cyclists to be severely injured or killed. In 2012, 41 of the 118 cyclists who were killed on Britain's roads were tested for their blood alcohol level and of these 24% had some alcohol in their blood and 15% were over the prevailing drink-drive limit. See DfT. Reported Road Casualties Great Britain 2013. Sept. 2014. Table RAS51009
Although no statutory limit for alcohol levels applies to cyclists, clearly, when using the roads with the inherent risk that brings from interaction with heavier moving vehicles, the advice must be don’t drink and cycle.