CO2emissions of vehicles
General introduction in figures
On average every car in Belgium covers around 15,000 kilometres (source: FPS Mobility and Transport). That corresponds to an annual CO2emission of approximately 2.8 tonnes. In addition we naturally use a lot of other vehicles. The impact of our method of transport on the total CO2emissions cannot be underestimated and is approximately 20 to 25% (the precise percentage may or may not depend on international aviation and shipping).
Table with the specific CO2emission per method of transport
Method of transport  CO2emission (g/km, tank to wheel)
 assumptions/sources 

Average for all passenger transport (2007)
 118
 Source: MIRAT 2008 
Average for all passenger transport (2002)
 132
 Source: MIRAT 2008 
Average questions
 127
 Diesel, 6.5 l/100 km (= 172 g CO2/km, based on 1.35 passengers)

Average new car
 100
 135 g/km, 1.35 passengers

Average questions, occupation during peak times
 143
 172 g/km, 1.2 passengers

Average standard bus
 75
 Diesel, 40 l/100km, 14 passengers

Hybrid standard bus
 60
 20% fuel reduction compared to standard bus

Average articulated bus
 63
 Diesel, 50 l/100 km, 21 passengers

Average tram theoretical (Ermine)
 23
 4 kWh/km, 60 passengers, 349 g CO2/kWh standard electricity mix Belgium, incl. nuclear energy (source: VITO, Auditconvenant)

Average tram in practice (Ermine, green power)
 1
 De Lijn buys 100% green power, mainly from hydropower stations (20 g CO2/kWh)

Metro
 30.5
 Source: MIVB

Newest hybrid car
 89
 New Toyota Prius, manufacturer's information

Electric car
 38
 15 kWh/100 km, standard mix of electricity in Belgium, 1.35 passengers

Train
 28
 Source: NMBS

Motorbike
 107
 Petrol, 4.5 l/100 km, 1.02 passengers

Scooter
 77
 Petrol, 3.2 l/100 km, no passengers

Cycle/on foot
 0

Methodological comment
The figures above only state the direct CO2 emissions ('tank to wheel' or TTW) through combustion. Indirect ('well to tank' or WTT), more specifically in the fuel production process, also consumes a large amount of energy. So at that time CO2 is also released. Different sources indicate the size of these, namely around 10 to 30% of the direct energy consumption.
Although the total of both sources of emission (WTT+TTW = WTW, or 'well to wheel') is actually the most accurate measure of the CO2 emissions of various vehicles, we have still used the TTWfigures above. For that reason the majority of figures can be found, e.g. on the advertising of car dealers or in different international reports.
Formula to calculate the CO2 saving
Our custom route planner calculates the saving in relation to CO2 emissions of a bus, tram and train compared to an average car.
We do not give any calculation for the CO2 savings for the proposed dialabus route.
After all that saving greatly depends on the occupancy of the bus, which varies greatly from trip to trip. In this way big differences may result in the distance to be covered and the route that a dialabus will cover during a trip.
Bus
We always use an average CO2 emissions of 70 g/km for a bus in our calculations. The routeplanner cannot know beforehand what type of bus will be used (standard bus, articulated bus, hybrid bus,…).
We take the CO2 emissions of an average car (127 g/km) and deduct the CO2 emissions of an average bus (70 g/km) from this. The number calculated is multiplied by the number of kilometres the passenger will travel by bus.
For instance if a passenger travels 12 km by bus, the calculation is as follows:
(12770) x 12 = 684
So a passenger saves 684g CO2 by travelling their 12 km by bus instead of by car.
Tram
We take the CO2 emission of an average car (127 g/km) and deduct the CO2 emissions of an average tram (1 g/km). The number calculated is multiplied by the number of kilometres the passenger will travel by tram.
For instance if a passenger travels 21 km by tram, the calculation is as follows:
(1271) x 21 = 2646
So a passenger saves 2.6kg CO2 by travelling their 21km by tram instead of by car.
Train
We take the CO2 emission of an average car (127 g/km) and deduct the CO2 emissions of an average train (28 g/km). The number calculated is multiplied by the number of kilometres the passenger will travel by train.
For instance if a passenger travels 38km by train, the calculation is as follows:
(12728) x 38 = 3762
So a passenger saves 3.7kg CO2 by travelling their 38km by train instead of by car.
How much is 1 tonne of CO2?
The best known way to compensate emissions of the greenhouse gas CO2 is by planting trees. Trees need CO2 to grow. In this process (photosynthesis) they use the carbon to grow: they capture the carbon (C) in Carbondioxide (CO2) in their biomass (wood, plant fibre, roots, ...). As a waste product they again emit oxygen (O2).
In that way trees (and plants) actually purify the air for humans. We actually do the opposite: we breath in air, use the oxygen O2 in it and breathe out more CO2. Daily we breathe about 900 grammes of CO2 per adult per year.
There are also lots of figures about how much CO2 a tree needs exactly to grow. From different sources (e.g. VBV, K.U.Leuven, UGent, …) we have selected the following information:
 1 hectare of woodland (in our climate) absorbs around 10 tonnes of CO2 on average per year or around 27.5 kg/day
 Per hectare of woodland there are about 300 to 500 trees
 1 fullygrown Flemish tree will absorb on average around 65 grammes CO2 (or 24 kg per year per tree)
 1 kilometre by car will take about 2 trees to neutralise the emissions  that is about half of that for 1 kilometre by bus