Rain, fog and floods

By the end of this topic you can

• You can adjust your speed and following distance for wet roads and fog.
• You can choose the right lights for fog and heavy rain.
• You can explain hydroplaning and how to respond if it happens.
• You can decide when to pull completely off the road and how to do it safely.
• You can check your brakes after driving through water.

What you need to know and understand

• Roads are often most slippery in the first minutes of rain, when water lifts oil and dirt off the surface.
• Use low beams in fog. High beams reflect off the water droplets and make it harder to see.
• Daytime running lights are not enough in fog, and on many cars they do not turn on the tail lights.
• Ontario, BC and Alberta require headlights when you cannot see clearly about 150 metres ahead; Manitoba's handbook uses 60 metres.
• Hydroplaning happens when the tires ride on a film of water and lose contact with the road.
• Never stop in a travel lane in fog. Pull completely off the road into a safe place.
• Avoid flooded roads; water can make your brakes ineffective.

Wet roads: speed, space and grip

When rain starts after a dry spell, the road can be greasy for the first 10 to 15 minutes, according to Nova Scotia's handbook. Slow down early and drive at a speed that lets you stop within the distance you can see. Leave more room behind the vehicle ahead; Nova Scotia's handbook suggests four seconds or more in rain, which also keeps you out of the spray.

Make every input small and gentle. Keep your wiper blades in good shape and replace them if they streak. Puddles can hide potholes, soak pedestrians and splash water onto your brakes, so steer around them when it is safe.

If the car starts to hydroplane

You may feel the steering go light, or hear the engine rev without the car speeding up. Worn tires, low tire pressure and higher speed all make hydroplaning more likely, so good tread and correct pressure are your best protection.

1. Take your foot off the accelerator and let the car slow down.
2. Hold the steering wheel steady. Do not brake hard or jerk the wheel.
3. Once the tires grip again, continue at a lower speed.

Fog: when to keep going and when to stop

Ontario's first advice is to avoid driving in fog and delay your trip if fog is forecast. If you are caught in it, slow down gradually, turn on your low beams (and fog lights if fitted), increase your following distance and avoid passing or changing lanes. Use the right edge of the road as a guide, not the centre line.

If the fog becomes too thick, signal, pull completely off the road into a safe parking area and turn on your hazard lights. Stopping on the road itself can start a chain-reaction crash. Do not speed up as soon as it seems to clear, because fog often comes in patches.

• Do: low beams, slow down gradually, bigger gap, clear windows with the defroster.
• Do not: high beams, sudden braking, passing, stopping in a live lane.

Flooded roads and wet brakes

No official handbook gives a safe depth of water to drive through. Treat any flooded road as closed and find another route. If you have driven through water, test your brakes gently when it is safe. Ontario suggests a quick, firm stop from 50 km/h to check that the car stops straight and the pedal feels firm; Manitoba suggests drying them by driving slowly and braking lightly. If the brakes still feel wrong, have them repaired.

Common mistakes

• Switching to high beams in fog to see further. Use low beams; high beams bounce back and dazzle you.
• Relying on daytime running lights in rain or fog. Turn on full headlights so your tail lights come on too.
• Braking hard when the car hydroplanes. Ease off the accelerator and keep the wheel steady.
• Stopping in the lane when fog thickens. Pull right off the road into a safe area with hazard lights on.
• Guessing that a flooded road is shallow enough. Turn around and take another route.

Test yourself: Rain, fog and floods

Answer each question, then read the explanation. Questions come in a random order each time.

Go deeper

• Driving in Fog, Rain and Floods in Canada