The Story of the Car Part 3: Accelerating

The Accelerator

The accelerator controls the supply of fuel to the engine and hence the speed or the power of the vehicle.

The vehicle itself is at it most stable (normally the safest) when under a constant acceleration in a straight line.

Acceleration sense is the driver’s ability to control their vehicle without using the foot brake in response to changing conditions. It should be a vital part of your driving plan. This sense is very closely linked to what is observed both inside your vehicle and outside. 

  • Outside by regulating your road speed you can improve safety, fuel economy and traffic flow.
  • Inside by glancing reference to your instruments you may maintain safety and legality.

Some factors affecting your acceleration sense.

Your speed will rise and fall with the gradient of the road, increasing down hill and decreasing up hill. The context of the road, moving from a fast moving road to a slow moving one will give a false sense of a safe speed. A wide road will seem slower than a narrow road because your points of reference are further away.

You must allow for other road users who share the road. For instance cyclists will get free speed going down hill.

Factors affecting acceleration

As you accelerate the weight of the vehicle is transferred from the front wheels to the rear wheels.


With front wheel drive vehicles:

  • Excessive acceleration can lead to front wheel spin.
  • This loss of traction when coming out of a junction may leave you in the path of an oncoming vehicle or other dangers.
  • It may also possibly lead to a condition called understeer on bends.
  • This is when your vehicle is going wide due to no grip from the front wheels.

With rear wheel drive vehicles:

  • The weight transfer when you accelerate on a rear wheel drive vehicle will initially help acceleration.
  • But harsh acceleration will result in wheel spin and the associated problems.
  • A loss of grip from the rear wheels when on a bend will result in oversteer.
  • This is when the rear wheels have lost grip and your vehicle spins out of control.

Use of the Accelerator.

Its use should be smooth and balanced with the other controls. As you increase or decrease the pedal pressure you will increase or decrease your vehicle speed.

As your speed increases you need to move up through the gears trading power for speed. By removing your foot from the accelerator there is a gradual slowing down of your vehicle. This is called engine compression and the lower your gear the more pronounced its effect.

Harsh use of the accelerator will lead to skidding by causing loss of traction due to wheel spin.

On an incline you may need to increase or decrease the pedal pressure to maintain a constant speed. If you are going up hill more pressure or down hill less. It is important to be in the correct gear to get the best response from the accelerator pedal.

Wearing the right foot ware will help you feel the pedal better. A closed shoe will protect your toes from stubbing. Shoe laces need to be done up. A shoelace caught in the door may mean your foot will not reach the brake when needed.

Syllabus For Learning To Drive – Car Controls & Instruments

For use of speed see also:

Syllabus For Learning To Drive – Use Of Speed

Syllabus For Learning To Drive – Dual Carriageways

Syllabus For Learning To Drive – Motorway Driving

Syllabus For Learning To Drive – Country Roads

© Liam Greaney