Anticipate traffic flow
- Read the road as far ahead as possible and anticipate the flow of traffic
- Act instead of react – increase your scope of action with an appropriate distance to use momentum. An increased safety distance equivalent of about 3 seconds to the car in front optimises the options to balance speed fluctuations in traffic flow – enabling steady driving with constant speed (see also additional explanation #1).
- Make maximum use of the vehicle’s momentum. Three different techniques are applicable (within 2 categories: (i) in gear; (ii) in neutral) – consider details of the car’s manual (see also additional explanation #2)
Additional Explanation #1:
Systematically increasing vehicle-to-vehicle distance within traffic flow significantly improves overall road safety. Increased safety distance equivalent of around 3 seconds to a vehicle driving ahead optimises options to act instead of only react and reduces risky situations. Key action: Step off the accelerator if traffic flow is slowing down to keep safety distance. With this simple action speed fluctuations in traffic can often be equalised and gently managed. As a result (strong) braking – while wasting built-up kinetic energy – can be often avoided as well as the need to accelerate after too hard deceleration.
Additional Explanation #2:
Making use of vehicles’ momentum means to use built-up kinetic energy of the car most efficiently. The overall goal is letting the car roll and driving steady speed whenever possible instead of braking and subsequently accelerate. Using vehicles momentum three different techniques are applicable – classified in two categories. It is important to consider specific advices of the individual car’s manual as well as strictly follow national legal requirements.
Using momentum can be realised within two different categories of driving techniques:
(i) in gear, (ii) in neutral – resulting into three specific advices.
(i) “using momentum in gear”
Driving technique #1: Let the car roll in gear. The speed of the vehicle will reduce due to the engine’s braking effect via mechanical friction (as gear engaged). Using the right gear unintended acceleration (e.g. while driving downhill) can be avoided. This technique is beneficial to saving fuel if the respective engine has a fuel cut-off mode and also while driving at higher speeds (consider advice for engine’s fuel cut-off).
(ii) “using momentum in neutral”
Driving technique #2: Let the car roll in neutral (no gear engaged with idling engine). The technique rolling in neutral with no gear engaged (with idling engine) makes better use of a
vehicle’s kinetic energy because there is no engine braking effect. This is beneficial for situations like approaching an obstacle or an identified stop (red traffic lights; Stop-sign). Thus, a relative long distance can be driven at quite constant speed without additional acceleration. While rolling in neutral the fuel consumption is defined by the idling engine alone. Especially for cars without engine fuel cut-off mode this is a good technique to use vehicles’ kinetic energy. But also for cars with fuel cut-off the option to letting the car roll without gear engaged can save fuel at typical low speed driving in cities (esp. when “stop-and-go” or only little faster). Engine’s fuel cut-off does not work at low RPM (check with the car’s manual for details), and is activated beyond a specific engine speed for the individual car. For safety reasons while driving downhill it is important to always stay in the right gear to avoid unintended acceleration.
Driving technique #3: Letting the car roll in gear, but with clutch engaged This technique is advisable in situations when it can be assumed that the ride can be continued soon in the same gear, and the use of the engine’s fuel cut- off and engine braking effect is not useful for good fuel efficiency.
Consider: Make use of the engines fuel cut-off whenever useful
It is important to know that inner mechanical friction (of engine/ transmission) wastes more kinetic energy than letting the car roll without traction (no gear engaged or clutch engaged). Engine fuel cut-off (if available for a specific car) operates only at certain speed range and revs area which differs from car to car. It is useful to know the car’s specifics as from the owner’s manual. At low RPM and low speeds (below 50 kph) – as typical for driving in cities – the use of the engine’s fuel cut-off is not always possible and useful. Especially for city driving it can be extremely difficult and distracting – safety risk! – to identify the right gear for making best use of the engine’s fuel cut-off. Relevant for safe driving is the fact that some modern cars accelerate automatically if the car falls below a specifically defined (engine) speed. This effect – if unintended – should be avoided because it raises fuel consumption and may lead to driver’s irritation (road safety issue). Older cars mostly have no engine fuel cut-off mode.
Note: All three techniques are to be applied strictly following the guideline “Safety First”.