AAATHE specified at very low levels so even small amounts of use could be  above the specified limits. The limits for certain medicines have  been specified at higher levels, above the levels generally found in  the blood of patients who have taken normal therapeutic doses. If you are found to have a concentration of a drug above its specified  limit in your blood because you have been prescribed or  legitimately supplied a particularly high dose of medicine, then you  can raise a statutory medical defence, provided your driving was  not impaired by the medicine you are taking.  Law RTA 1988 sects 4 & 5  4.Before setting off  97. Before setting off.   You should ensure that  ● you have planned your route and allowed sufficient time  ● clothing and footwear do not prevent you using the controls  in the correct manner  ● you know where all the controls are and how to use them  before you need them. Not all vehicles are the same; do not  wait until it is too late to find out  ● your mirrors and seat are adjusted correctly to ensure  comfort, full control and maximum vision  ● head restraints are properly adjusted to reduce the risk of neck and spine injuries in the event of a collision  ● you have sufficient fuel before commencing your journey,  especially if it includes motorway driving. It can be  dangerous to lose power when driving in traffic  ● ensure your vehicle is legal and roadworthy  highwaycodeuk.co.uk 46 