201: You MUST use headlights when visibility is seriously reduced, generally when you cannot see for more than 100 metres (328 feet). You may also use front or rear fog lights but you MUST switch them off when visibility improves (see Rule 211).
Law RVLR regs 25 & 27

202: In wet weather, stopping distances will be at least double those required for stopping on dry roads (see Stopping Distances). This is because your tyres have less grip on the road. In wet weather

• you should keep well back from the vehicle in front. This will increase your ability to see and plan ahead
• if the steering becomes unresponsive, it probably means that water is preventing the tyres from gripping the road. Ease off the accelerator and slow down gradually
• the rain and spray from vehicles may make it difficult to see and be seen.

203: In winter check the local weather forecast for warnings of icy or snowy weather. DO NOT drive in these conditions unless your journey is essential. If it is, take great care. Carry a spade, warm clothing, a warm drink and emergency food in case your vehicle breaks down.

204: Before you set off

• you MUST be able to see, so clear all snow and ice from all your windows
• you MUST ensure that lights and number plates are clean
• make sure the mirrors are clear and the windows are de-misted thoroughly.
  Laws CUR reg 30 & RVLR reg 23

Make sure your windscreen is completely clear

205: When driving in icy or snowy weather

• drive with care, even if the roads have been gritted
• keep well back from the vehicle in front as stopping distances can be ten times greater than on dry roads
• take care when overtaking gritting vehicles, particularly if you are riding a motorcycle
• watch out for snowploughs which may throw out snow on either side. Do not overtake them unless the lane you intend to use has been cleared
• be prepared for the road conditions changing over relatively short distances.

206: Drive extremely carefully when the roads are icy. Avoid sudden actions as these could cause a skid. You should

• drive at a slow speed in as high a gear as possible; accelerate and brake very gently
• drive particularly slowly on bends where skids are more likely. Brake progressively on the straight before you reach a bend. Having slowed down, steer smoothly round the bend, avoiding sudden actions
• check your grip on the road surface when there is snow or ice by choosing a safe place to brake gently. If the steering feels unresponsive this may indicate ice and your vehicle losing its grip on the road. When travelling on ice, tyres make virtually no noise.

207: High sided vehicles are most affected by windy weather, but strong gusts can also blow a car, cyclist or motorcyclist off course. This can happen at open stretches of road exposed to strong cross winds, or when passing bridges or gaps in hedges.

208: In very windy weather your vehicle may be affected by turbulence created by large vehicles. Motorcyclists are particularly affected, so keep well back from them when they are overtaking a high-sided vehicle.

209: Before entering fog check your mirrors then slow down. If the word 'Fog' is shown on a roadside signal but the road is clear, be prepared for a bank of fog or drifting patchy fog ahead. Even if it seems to be clearing, you can suddenly find yourself in thick fog.

210: When driving in fog you should

• use your lights as required in Rule 201
• keep a safe distance behind the vehicle in front. Rear lights can give a false sense of security
• be able to pull up within the distance you can see clearly. This is particularly important on motorways and dual carriageways, as vehicles are travelling faster
• use your windscreen wipers and demisters
• beware of other drivers not using headlights
• not accelerate to get away from a vehicle which is too close behind you
• check your mirrors before you slow down. Then use your brakes so that your brake lights warn drivers behind you that you are slowing down
• stop in the correct position at a junction with limited visibility and listen for traffic. When you are sure it is safe to emerge, do so positively and do not hesitate in a position that puts you directly in the path of approaching vehicles.

211: You MUST NOT use front or rear fog lights unless visibility is seriously reduced (see Rule 201) as they dazzle other road users and can obscure your brake lights. You MUST switch them off when visibility improves.
Law RVLR regs 25 & 27

212: Keep your vehicle well ventilated to avoid drowsiness. Be aware that the road surface may become soft or if it rains after a dry spell it may become slippery. These conditions could affect your steering and braking.