Table 1 Description of evaluated predictor variables

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, PM_2.5 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