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Tool 13 - Calculating Air Pollution Near Roads Using CAR-International Model
CAR International is a simple to use air quality dispersion model. This model has been developed by the Dutch Institute Environmental, Energy and Process Innovation (TNO) in cooperation with the Netherlands National Institute of Public Health and Environmental Protection (RIVM). Although CAR International is no longer supported, it is still helpful in calculating concentrations of a number of air pollutants such as:
- nitrogen dioxide (NO2)
- carbon dioxide (CO)
- benzene
- lead
- black smoke
The model, CAR International, is contained in this CD-ROM. Please read the instructions for installation and the guidance notes for CAR International.
Results of CAR International
The level of pollution of a given pollutant near roads is calculated
at a distance to the road axis ranging from 5 to 30 meters. The following
concentrations of the above-mentioned five pollutants can be calculated
with CAR International:
1. Average yearly concentration in µg/m3
2. 98 percentile of average concentrations over 1 hour in µg/m3
3. 98 percentile of average concentrations over 8 hours in µg/m3
4. 98 percentile of average concentrations over 24 hours in µg/m3
Average annual and peak concentrations of CO, NO2 and benzene can subsequently be compared with the (WHO) air quality guidelines in order to identify potential air pollution problems.
The model
This version of the CAR International model requires Microsoft Windows
operating system (95, 98, 2000, XP).
Please extract the car_int.zip file
and click on start.bat. Please also refer to the quick
manual.
The following window will open.
Table 13.1 Entry pages of Car International
Input Data:
The model is very easy to use, as long as the necessary parameters and input data are available. It requires few data, as follows:
Table 13.2 Factors That Users Can Change
| PARAMETER | UNIT |
| Emission Factors for CO, NOx and Benzene | µg/m/s |
| Fraction of Directly emitted NO2 | --- |
| City/ Regional Background Concentration (CO, NO2 and Benzene) | µg/m3 |
| Yearly average wind speed (at 10 meters height) | m/s |
Table 13.2 above presents those factors that users can change. These factors have been fixed based on an average Dutch situation. In case of developing countries, the factors have to be adopted locally, especially the emission factors.
The following tables give the necessary parameters that have to be fed
into the model in order to calculate the pollutant concentrations.
Given below are the specifications:
1. Speed Types: CAR International uses four speed types
| Type | Average Speed (Km/h) | Description |
| A | 100 | Representative for the average speed of vehicles in a roadway |
| B | 44 | Representative for the average speed of vehicles on a road with a maximum speed of 70 km/h |
| C | 22 | Representative of the average speed of city traffic |
| D | 13 | Representative of the average of stagnating traffic, due to stopping for traffic lights or road crossings |
2. Tree Factor: The tree factor represents the influence of trees on the dispersion of air pollutants. There are three options described as below:
| Value | Description |
| 1.00 | A road through an open field lined with very few or no buildings within a distance of 100m from the traffic lanes |
| 1.25 | Trees on one side of the street |
| 1.50 | Trees on both sides of the road, with the tops touching each other |
3. Road Types: CAR International Distinguishes between five road types
| Type | Description |
| 1 | A road through an open field lined with very few or no buildings within a distance of 100m from the traffic lanes |
| 3a | Roads lined with buildings on both sides. The buildings are more than 3m high and the distance between them and the center of the carriageway is less than 3 times the height of the buildings |
| 3b | Roads with buildings on both sides. The buildings are more than 3m high and the distance between them and the carriageway center is less than 1.5 times the height of the buildings |
| 4 | Roads lined with buildings on one side. The buildings are more than 3m high and the distance between them and the road axis is less than 3 times the height of the buildings |
| 2 | All roads differing from types 1, 3a, 3b or 4 |
Table 13.3 Results
The TNO Environmental Sciences developed the CAR International computer programme. For further information on this programme, please contact TNO-MEP, Department of Environmental Quality, P.O Box 6011, 2600 JA Delft, The Netherlands. Tel +31-15-2696035, fax +31-15- 2616812, Email: O.Weinhold@mep.tno.nl
Using the Spreadsheet
The following example from Dar es Salaam is based on a speadsheet which uses the same parameters as the above model. Air pollution concentrations for five streets in Dar es Salaam are calculated:
- Getting the Data of Dar Es Salaam as Input Data for CAR International (like number of cars passing and the average emission factors)
- Illustrating an easy way of adapting CAR International to local situation
by changing the the emission factors (as these are default Dutch currently).
The input data of that sheet have been used in CAR International (for
example in Dar es Salaam).
