Explanation: A long vehicle may have to straddle lanes on, or approaching, a roundabout. This is to prevent the rear wheels from going up onto the kerb. If you're following a long vehicle, stay well back and give it plenty of room.
Category: Band 1 road procedure
References: The official DVSA guide to driving: section 8, Highway code: rule 78, Highway code: rule 187, Highway code: rule 188