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We have spent some time discussing the basics of The System of Car Control, and in the last issue of One Way we moved into the advanced phase. One advanced aspect that associates often find difficult to grasp is how fast to go into a bend: they either go in too fast and have to reduce speed during the bend, or slow right down beforehand and crawl through it. To get this right, you have to consider the basic safety rule and the limit point.
The basic safety rule in driving is:
Always be able to stop on your own side of the road in the distance you can see to be clear.
That means that you have to approach a bend at such a speed that you could stop safely if there was an obstruction, such as a broken-down vehicle, a fallen tree or even a small child, in the road just round the bend. If everyone always observed that basic rule, there would be far fewer ‘accidents’ (or crashes, as the police now term them to indicate that there is very rarely anything ‘accidental’ about them – they are nearly always the result of driver error).
The other thing to bear in mind in a bend is the Limit Point – that is, the farthest point along a road to which you have an uninterrupted view of the road surface. It could be caused by a bend, and is then the point at which the two verges appear to meet. Sometimes it is caused by the brow of a hill, and it is then the false horizon where the road disappears beyond the brow.
The need to be able to stop on your own side of the road in the distance you can see to be clear determines how fast you can go. The more distant the limit point the faster you can go because you have more distance to stop in. The closer the limit point the slower you can go because you have less space to stop in.
Let us consider the approach to a left-hand bend on a single-carriageway country road. As you approach the bend, the left and right-hand verges appear to meet at some point ahead of you. You therefore reduce speed, using acceleration sense and braking if necessary. You might also position the vehicle towards the centre of the road for maximum view to the left, being alert to the possibility that an approaching vehicle might drift over the centre line towards you. Continue to reduce speed as the limit point moves towards you. At some stage, the limit point will stop moving towards you. When it starts to move away at the same speed as you are travelling, you have exactly the right speed for the bend – the limit point will be at a constant distance from you as you move through the bend. Eventually, as the bend straightens out, the limit point will appear to move away from you. You can now accelerate gently, and then more vigorously as you enter the straight road after the bend, until you reach a speed limit or another bend.
The same principle applies for a right-hand bend – this time you might choose to position your vehicle close to the nearside verge for a better view into the bend, and to avoid drifting over the centre-line into the path of oncoming vehicles.
For a series of bends, you apply the limit-point method described above to each one in turn. Select your position in the road, reduce speed until the limit point stops getting nearer, match your speed to the limit point and remain at that speed through the bend, accelerate gently as the limit point moves away, and do it again for the next one. For maximum flexibility, you need to choose a gear that gives you the best control – perhaps third gear, or even second, in a five-speed manual gearbox, and a low gear hold (third or second) in an automatic. Otherwise you will find yourself having to brake hard for each bend, and that can upset the balance of the car.
If you know a road with a series of bends you can use it for practice. Chose a time when there is little traffic and drive through the bends using the limit-point technique. Then drive back in the other direction. You might want to experiment with different gear selections, especially in an automatic if you normally leave the selector in the Drive position – D. You will probably find that if you have the right gear you can negotiate the series of bends using acceleration sense, with very little braking at all, and it’s very satisfying when you get it right. On an unfamiliar road you can often use cross views during the information phase, to detect the line of the road and the direction and severity of the bends. Bend warning signs (with a red triangle) and black and white ‘chevrons’ also give an indication of the sharpness of the bends – they tend to be relative, so that a chevron sign before a particular bend indicates that this bend is sharper than the previous one without a sign.
For hump-backed bridges and brows of hills, use the same method. Slow down on the approach so that you can observe the basic safety rule, and accelerate again only when you have crested the hump and can again see the road ahead.
Roadcraft
covers the whole topic of limit points in Chapter 8, Cornering, and there is a
good series of diagrams of the limit-point technique on pages 116-117. The
Roadcraft
video also shows several examples of this technique in operation, with the usual
detailed commentary to explain what is happening. It’s rather easier to
do than it is to describe.