Table 1.
Description of evaluated predictor variables
| Source data | Variable name(s)a | Description | Unit | Direction of effect | Buffer sizes (m) |
|---|---|---|---|---|---|
| Building density | BUILDINGS_X | Total area covered by buildings | m2 | + | 25, 50, 75, 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 |
| Population grid | POP_X | Population count | N(umber) | + | 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 |
| CORINE Land Cover b | LDRES_X | Low density residential | m2 | + | 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 |
| HDRES_X | High density residential | m2 | + | 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 | |
| AIRPORT_X | Airport | m2 | + | 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 | |
| INDUSTRY_X | Industry | m2 | + | 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 | |
| NATURAL_X | Natural | m2 | - | 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 | |
| PORT_X | Port | m2 | + | 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 | |
| URBGREEN_X | Urban green | m2 | - | 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 | |
| UGNL_X | Urban green and natural land | m2 | - | 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 | |
| WATER_X | Water | m2 | +/− | 100, 150, 200, 250, 300, 500, 1000 | |
| Road network | ROADLENGTH_X | Total lengths of all roads | m | + | 25, 50, 75, 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 |
| MAJROADLENGTH_X c | Total lengths of all major roads | m | + | 25, 50, 75, 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 | |
| TRAFLOAD_X | Total traffic load of roads (sum of (traffic intensity * length of each segment)) | Veh · day−1 · m | + | 25, 50, 75, 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 | |
| TRAFMAJORLOAD_X c | Total traffic load of major roads (sum of (traffic intensity * length of each segment)) | Veh · day−1 · m | + | 25, 50, 75, 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 | |
| HEAVYTRAFLOAD_X | Total heavy traffic load of roads (sum of (traffic intensity * length of each segment)) | Veh · day−1 · m | + | 25, 50, 75, 100, 150, 200, 250, 300, 500, 1000, 2000, 5000 | |
| TRAFNEAR, TRAFMAJOR c, HEAVYTRAFNEAR | (Heavy) traffic intensity on the nearest (major) road | Veh · day−1 | + | N/A | |
| INTINVDIST, INTINVMAJDIST c, HEAVYINTINVDIST | Traffic on the nearest (major) road * inverse distance | Veh · day−1 · m−1 | + | N/A | |
| INVDIST, MAJINVDIST c | Inverse distance to the nearest (major) road | m−1 | + | N/A | |
| DHM Altitude grid | ALT, LOG_ALT, SQRT_ALT | Altitude, log(altitude) and sqrt(altitude) | m | - | N/A |
| Dispersion model estimates | NO2_2010, PM25_2010, PM10_2010 | Pollumap 2010 prediction for NO2, PM2.5 and PM10 | μg/m3 | + | N/A |
| Area indicator | Area_BS, Area_DA, Area_GE, Area_LU, Area_MO, Area_PA, Area_WA | Dummy variable for presence of a measurement site in the study areas of Aarau, Basel, Davos, Geneva, Lugano, Montana, Payerne, Wald. The reference is Aarau | Not applicable | +/− | N/A |
aThe suffix “X” is replaced by the buffer size in meters to get the full variable name (e.g. BUILDINGS_100 = area covered by buildings in a 100 m buffer); bCORINE classes were defined as previously in the APMOSPHERE [24, 45] and ESCAPE [5, 6, 46] projects; c Where major road is defined as a road with ≥5000 vehicles/24 h