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 

