Sadly, the number of serious accidents each year in the UK remains high, despite an emphasis on road safety from both our government and the EU, and recent advances in vehicle technology.
One aspect of driving that continues to be a problem area is cornering. But it's not always simply driving round a bend - the physical act of the vehicle being steered in a curved path that is too tight for its speed is the real issue, and that can happen even on a straight road.
One aspect of driving that continues to be a problem area is cornering. But it's not always simply driving round a bend - the physical act of the vehicle being steered in a curved path that is too tight for its speed is the real issue, and that can happen even on a straight road.
Sometimes it's a sudden lane change on a motorway - a swerve. Or a late decision to use an exit slip road - from the outside lane in some cases. But whatever the cause, the driver should always think of the Friction Circle, an illustration of the finite nature of friction and how the Laws of Physics apply to us all.
Even with ESC (Electronic Stability Control) a car is not infallible - the Laws are still there. Each tyre has a maximum amount of friction available, which can be used for cornering, driving and braking, or, as in most cases, a combination of cornering and one of the other two.
This is an extremely important point and it affects all vehicles (although it seems to cause more problems with the drivers of front wheel drive cars).
The friction circle shows that if you are braking hard, you have little or no friction left for cornering. ABS disguises this by extending the braking distance while allowing cornering to continue. Without ABS, the wheels lock and the vehicle goes in a straight line - at maximum braking.
This is an extremely important point and it affects all vehicles (although it seems to cause more problems with the drivers of front wheel drive cars).
The friction circle shows that if you are braking hard, you have little or no friction left for cornering. ABS disguises this by extending the braking distance while allowing cornering to continue. Without ABS, the wheels lock and the vehicle goes in a straight line - at maximum braking.
And don't forget - the Laws of Physics always apply. ABS, traction control and ESC are all limited by nature.
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| 1. The vehicle is cornering hard and the driver, probably realising the speed is too great, applies the brakes. The vehicle pushes out. 2. The vehicle is travelling too fast for the bend and the driver lifts of the accelerator. On this FWD vehicle, friction that was being used for drive is 'given back' to the front tyres, so their cornering ability (relationship between cornering force and slip angle) increases. The vehicle 'cuts in'. Weight is also transferred forward, adding to the cornering ability of the front tyres. At high speeds, this can happen very quickly and the driver's reaction - to counter steer, rapidly - can send the vehicle completely out of control. 3. While approaching the bend, the driver brakes to the correct speed for the bend, selects the right gear for the speed, and then drives through. Tyre friction is being used mostly for cornering with very little needed for drive - perfect. 4. The driver accelerates hard in the bend and the front tyres take friction from cornering - the car understeers out. |
