DL - Driving in difficult conditions

In Finland we have a short summer but a long winter. Even in October the roads can be slippery and the darkness also makes driving difficult. It is important to know how to adjust your driving speed to suit the situation. The driver must be able to stop the vehicle in all foreseeable situations within the visible distance. If visibility is limited due to bad weather or darkness, you must drive at a sufficiently low speed.


The importance of driving speed

The stopping distance of a car consists of a reaction distance and a braking distance. The length of the reaction distance is affected by the driver's driving condition. A tired driver cannot react as quickly as a refreshed driver. Normally, the reaction time is 1 - 2 seconds. The length of the braking distance is affected by the slipperiness of the road surface (friction), the condition of the car's tires and brakes. However, the driving speed is the biggest factor affecting the car's braking distance. When you slow down your driving speed by a quarter, the braking distance is almost halved.

Driving speed 80km/h
Braking distance = 27 meters
 Driving speed 60km/h
Braking distance = 15 meters
Experiment and compare how speed affects the stopping distance of a car on different friction surfaces with the traffic safety stopping distance animation.extrat.liikenneturva.fi/pysahtymismatka-auto/




Driving on slippery surfaces

In the middle of winter, it is clear that the roads are slippery, but the slippery condition can surprise you even before winter. Black ice forms when the weather is damp in the evening and the temperature drops close to zero degrees in the morning. Test the road surface for slipperiness when you walk to your car. In addition to slipperiness in winter, falling snow, snow accumulated on the road and snow piles plowed along the edges of the roads can cause problems. Traffic signs and road markings can be difficult to see.



Winter tires must be installed under the car from November to March whenever the weather requires it. If necessary, winter tires can also be used at other times. Most drivers drive with studded tires in winter. Studded tires offer good grip on icy roads, but on dry asphalt they damage the road surface and the studs also wear out. You can use studless winter tires (so-called friction tires) without restrictions, but friction tires are not suitable for summer weather. On wet roads, the grip of a soft winter tire is not sufficient.



The minimum tread depth of the main grooves of the tires is 1.6 mm for summer tires and 3.0 mm for winter tires. Also remember to check the tire pressure regularly and increase the air pressure when the car is fully loaded.

ABS brakes, traction control and stability control

ABS brakes make it easier to control the car during difficult braking. The anti-lock ABS brake system does not actually shorten the braking distance, but it allows you to brake even when cornering. Without ABS brakes, braking and steering at the same time would be impossible. If the yellow ABS brake light comes on, you can continue your journey, but have your car repaired as soon as possible.

The TC/ASR traction control system reduces tire squealing when starting off. The system brakes the driving tires or cuts power. The ESP/ESC stability control system aims to reduce steering errors made by the driver in close-range situations. The stability control system uses several sensors to monitor the car's position, tire rotation and attitude. If the road is slippery, the assistance systems do not turn winter into summer.


Driving in the dark

The driver must make sure that they always use their headlights when driving in the dark, at dusk, in fog, in snow or in rain. Lights must also be used in tunnels. Cars now have DLR daytime running lights as standard, so the rear lights may not be automatically on.

1. Headlights off
2. Front and rear lights (parking lights)
3. Headlights (low beam)
Always use your high beams when driving on dark, unlit roads, when there is no oncoming or preceding traffic. You can turn on your high beams by pushing or pulling the indicator lever. Using your high beams will give you a range of around 100-150 metres. Using your low beams will only give you a range of around 50 metres.




If you have to stop your car on a dark road, turn on your parking lights. Also turn on your hazard lights if you have to stop, for example because of an accident. Place a warning triangle about 100 - 200 meters away from your car.

You can use your hazard lights to warn other traffic if you have to stop your car in a dangerous place. For example, on a motorway, it is a good idea to turn on your hazard lights shortly before stopping.

Reflector

Remember to use a reflector or several reflectors whenever you are driving on a dark road. It is also important to use a reflector on a lighted road. Try out visibility in the dark and the benefits of a reflector:






DL_FREE book is freely available for driving studies and includes linked videos. Copying the book and its parts is prohibited. The book is provided to driving school students by DL Oppimaterialit and SG-IAF.