When you are driving, the distance you can see ahead of you changes all the time because of:
- Curves
- Other vehicles
- Weather conditions
- Changes in elevation
- Other obstructions
- Sun dazzle
- Light levels
It’s dangerous if the distance you can see ahead drops below 5 seconds because you need time to react and stop you should come across a hazard in the road. You’ll get used to judging this once you’re an experienced driver, but while you’re learning it’s good to practice seeing how far this is by picking a point on the road ahead then counting 1001, 1002, 1003, 1004, 1005. This is approximately 5 seconds. If you reach that point before you’ve finished counting, you’re travelling too fast.
Curves: As the road curves away from you, you will see the outside corner of it. For right-hand curves, you’ll see further around the corner if you are positioned to the left of your lane. For left-hand curves, you’ll see further around the corner if you are positioned closer to the centre line. As you approach the corner, this vanishing point will appear to move closer to you. At the point where you are around the tightest part of the corner and it starts to open out, the vanishing point will move away from you until you are on a straight piece of road again and you can see to the next corner.
Other vehicles: The closer you follow another vehicle, the less view you have ahead of it. Of course, vehicles also come in the opposite direction. While you are on a right-hand turn, large vehicles coming towards you hide your vision of the vanishing point.
Weather conditions: Sudden fog and mist will reduce the distance you can see ahead. With fog, don’t put your high beam headlights on as the fog reflects the light back at you. Rain has a similar effect of reducing visibility
Changes in elevation: As you come up to the brow of a hill you won’t be able to see over it.
Other obstructions: Signage, street furniture and foliage can restrict your view
Sun dazzle: The sun can be blinding when it’s low. This can cause your to need your sunblind which might restrict your vision to less than 50m ahead.
Light levels: At night, on unlit roads, the features of the road can blur into the verge and your headlights won’t have enough power to illuminate everything for a long distance ahead.
If you experience any of the above and you can’t see, simply slow down until you can see 5 seconds ahead.
Darren is an expert on driving and transport, and is a member of the Institute of Advanced Motorists
