Evaluation of Land Use Regression Models for Nitrogen Dioxide and Benzene in Four US Cities

Table 1

Group types for potential predictor variables^a.

Predictor variable groups and subgroups from GIS	El Paso	Detroit	Dallas	Cleveland
(1) Traffic
Distance to nearest low-traffic road (m)^b	X^c
Distance to nearest medium-traffic road (m)		X^d		X^e
Distance to nearest high-traffic road (m)	X^f	X^f	X^g	X^h
Traffic intensity within set buffers (vehicles per day/km)	X	X	X	X
Length of local roads within set buffers (m)				X
Length of secondary roads within set buffers (m)				X
(2) Area and point
Open area within set radii (km^2)				X
Population density within census block group or set radii	X	X	X	X
Point source emitters (categorical or continuous)	X^i	X^i	X^i	X^j
(3) City specific
Elevation (m)	X
Distance to nearest international border crossing (m)	X	X
Distance to airport (km)				X
Distance to lake (km)				X
(4) Season			X	X

^aSpecific variables and their sources are detailed elsewhere for El Paso [7], Detroit [8], Dallas [9], and Cleveland [10]. ^bUnits in parentheses. ^croad > 10,000 vehicles/day. ^d  ≥50,000 vehicles per day. ^e  ≥40,000 vehicles/day. ^f  ≥90,000 vehicles/day. ^g  ≥140,000 vehicles/day. ^h  ≥70,000 vehicles/day. ⁱDistance (m) from emission sources. ^jEmission sources within set buffers.