Situation	Influence sur la consommation	Influence sur l'environnement
first kilometre after cold starting	+ 50 %
urban travel	+ 20 to 40 % more in heavy traffic
under-inflated tires	+ 5 %
(empty) roof rack	+ 10 %
"aggressive" as opposed to "smooth" driving	+ 20 to 40 %
poorly tuned or dirty engine	10 % or possibly up to + 50 %

Driving economically
By driving "smoothly" you will reduce your gas budget and extend the life of your vehicle.
A few tips about smooth and economical driving
The key word in economical driving is anticipation.

	Start out slowly: you do not have to let your car idle for several minutes in order for it to warm up. It is better to start driving slowly, with no sudden accelerations, for the first few kilometres.
	Manoeuvre without jerks: It is of no good to repeatedly punch the accelerator when manoeuvring (when parking, when leaving a parking space or the garage…). This way of driving does not make it easier to manoeuvre and causes over-consumption.
	Anticipate acceleration and braking: quick and sudden acceleration (especially when driving in urban areas) increases consumption. Gradual and anticipated braking is less energy-consuming and easier on the vehicle.
	Use a higher gear at any given speed: The engine will have a lower power reserve with fewer r.p.m. and it will be less consuming. You can gear down if you need more power, for example when passing another car.
	Check your tire pressure: With under-inflated tires (0.3 bar less than required) consumption increases by 5% due to increased friction between the tire and the road and your safety is at risk. Conversely over-inflated (0.2 to 0.3 bar) tires reduce consumption without affecting safety.
	Take care of your engine: Properly working ignition and fuel systems will keep you from consuming more fuel than required. A clogged-up air filter prevents air from reaching the cylinders effectively and results in increased consumption.
	Remove the roof rack when it is not being used: Objects on the roof of a vehicle slow it down (due to wind resistance). Thus roof racks should not be left on the vehicle when not needed.
	Drive at moderate speed: high speeds are a major source of over-consumption, especially when it comes to compact cars lacking in power (the engine revs at high speed), and to poorly aerodynamic vehicles like four wheel drives. If your car uses 8 litres per 100 kilometres when travelling at a speed of 110 km/h then it will use 10 litres to travel at a speed of 125 km/h, which is 20% more.
	Use the air-conditioning as needed: Air-conditioning is a major consumption factor in vehicles because when decreasing the interior's temperature by 8° C consumption is increased by 15% to 25%. In town, these figures can be significantly higher.
	When possible, use alternative means of transportation: Among all means of land transport, private cars are the most harmful to the environment. Overall a person travelling by bus, on a given route, generates 10 times less atmospheric pollution and uses 3 times less primary energy than a person travelling the same route, alone, by car.

Car alternative
Walking and cycling
The bicycle is the easiest and most economical means of transportation. Over a short distance, of a few kilometres, you will sometimes travel faster than by car if you take into account the time required to start out, the time lost due to traffic, and the time spent looking for a parking space which may not even be close to your final destination. Cycling is also an ideal way to exercise, something which an office job does not allow you to do during your working day.
Walking provides the same health benefits, but the distance that one can reasonably travel on foot is, obviously, shorter (around one kilometre).

Public Transportation (bus and train)
Public transportation is a great alternative to the car as well as more economical and less stressful. At times of heavy traffic (rush hours) you will travel as quickly as by car and without the annoyance and fear of an accident. It is worth having a look at the rates charged by public transportation companies for regular users.
In terms of energy efficiency there is a 2 to 2.5 ratio between public transportation and a private car, which means that to transport the same number of people over a given distance the bus would use 2 to 2.5 times less energy.
Being more efficient, public means of transportation pollute less and are more economical.
One could say that by using public transportation the disadvantages (such as lack of privacy, etc.) are individualised and the advantages (less pollution, fewer traffic jams…) collectivised whereas by using a private car the advantages (personal convenience…) are individualised and the drawbacks (pollution, urban congestion…) are collectivised.