The aim of our study was to assess exposure to nitrogen oxides in the city of Barcelona and see how the exposure and health effects or the exposure were affected by the introduction of a Bicycle programme (called Bicing)  in the city.

First the exposure to nitrogen oxides was assessed using dispersion modelling. The TNO model URBIS was used. This model combines three models:

1) a model to estimate concentrations caused by traffic on motor ways

2) a model to estimate concentrations caused by traffic in  streets (the CAR model)

3) a model to estimate concentrations caused by area sources (housing etc) and point sources (industry)

The model uses data obtained by measurements to determine the background concentrations of NOx. The contribution by the other sources is derived using the three models described above. The concentration is obtained adding up the contributions of all sources. By doing this the concentration is calculated for every location in the city.

All models above need emissions and other data As an example here it is explained how the contribution by traffic on roads is estimated. This is especially illustrating because the bicing programme will only affect only these contributions

The study focuses on the city centre because this is where the bicing programme will take place. The models mentioned above need the following information:

• Emissions of nitrogen oxides to air by traffic in every street. This data is derived from traffic intensities for major streets provided by the city counsel. To calculate the traffic intensities in the smaller roads an approximation was used based on the relation between traffic density and street width. Emission is derived from traffic intensities and emission factors from the Copert data base.
• The model needs characteristics of the streets to estimate the dispersion. These characteristics include parameters such as street width and number of trees in the streets. These parameters were derived from samples of Google street view.
• Average wind speeds in the city. This parameter may be derived from any wind speed monitor .
• The model is then run and the concentration on each location is calculated. 
  
  
  

  • The quality of the modelled concentrations was tested by comparison with concentrations measured in the city centre using passive samplers on a large number of sites. The comparison was quite well.

  
  

   

  
  

  The impact of the bicing programme on the exposure was then estimated. This was done assuming that every bike would have the effect of taking one car of the street. This leads to a lower concentration of nitrogen oxides. The health impact of the exposure to NOX was estimated for the two situations: without and with the bicing programme.

  
  

  
  

  • a reference to a description of the CAR model (somewhere else in the toolbox)
  • a reference to the case study report (some where else in the toolbox)