agricultural vehicles such as a tractor with a trailer or other  fixed equipment, will obscure your view of the road ahead  and there may be another slow-moving vehicle in front  highwaycodeuk.co.uk 87  165. You MUST NOT   overtake  ● if you would have to cross or straddle double white lines  with a solid line nearest to you (but see Rule 129)  ● if you would have to enter an area designed to divide traffic,  if it is surrounded by a solid white line ● make sure that you have enough room to complete your  overtaking manoeuvre before committing yourself. It takes  longer to pass a large vehicle. If in doubt do not overtake  ● not assume you can follow a vehicle ahead which is  overtaking a long vehicle. If a problem develops, they may  abort overtaking and pull back in. 