. Author manuscript; available in PMC: 2014 Oct 23.

Published in final edited form as: Accid Anal Prev. 2013 Mar 13;55:135–143. doi: 10.1016/j.aap.2013.03.001

Table 2.

Relative risks associated with ZIP code characteristics, among total injury crashes and crash types.

Variable	Total injury crashes (relative to total population) median (95% C.I.)	Had been drinking crashes (relative to all injury crashes) median (95% C.I.)	Single-vehicle night crashes (relative to all injury crashes) median (95% C.I.)
Bar/pub density (100s/sq. mile)	0.707 (0.357, 1.437)	2.050 (1.419, 2.960)^a	2.133 (1.092, 4.196)^a
Restaurant density (100s/sq. mile)	2.157 (1.800, 2.629)^a	1.064 (0.954, 1.190)	0.981 (0.803, 1.202)
Off-prem. density (100s/sq. mile)	0.329 (0.205, 0.478)^a	0.871 (0.717, 1.073)	0.180 (0.126, 0.260)^a
Any casinos (dummy variable)	0.982 (0.887, 1.086)	1.055 (1.008, 1.106)^a	0.980 (0.925, 1.039)
Total retail density (100s/sq. mile)	1.088 (1.059, 1.124)^a	0.947 (0.930, 0.965)^a	0.916 (0.882, 0.949)^a
Real HH income ($10,000s)	0.985 (0.977, 0.995)^a	0.972 (0.968, 0.977)^a	1.002 (0.997, 1.008)
Average HH size	0.833 (0.802, 0.856)^a	1.129 (1.095, 1.153)^a	1.144 (1.115, 1.172)^a
Proportion White	0.727 (0.639, 0.834)^a	1.704 (1.589, 1.830)^a	1.379 (1.279, 1.500)^a
Proportion Black	2.183 (1.689, 2.789)^a	1.381 (1.244, 1.543)^a	1.432 (1.251, 1.642)^a
Proportion Hispanic	2.440 (2.047, 2.850)^a	1.534 (1.446, 1.632)^a	0.943 (0.867, 1.025)
Proportion Male	0.066 (0.053, 0.086)^a	2.153 (1.699, 2.592)^a	4.238 (3.300, 5.478)^a
Proportion aged 20–24	52.910 (37.626, 83.739)^a	0.489 (0.367, 0.654)^a	0.530 (0.392, 0.727)^a
Proportion aged 25–44	22.092 (15.997, 31.852)^a	0.906 (0.701, 1.156)	0.615 (0.491, 0.785)^a
Proportion aged 45–64	7.616 (5.872, 10.930)^a	2.668 (2.059, 3.303)^a	2.505 (1.989, 3.187)^a
Proportion aged 65+	7.603 (5.634, 10.631)^a	0.872 (0.682, 1.095)	0.819 (0.668, 1.042)
Pop. density quintile 2 dummy	0.259 (0.247, 0.272)^a	1.115 (1.080, 1.152)^a	0.880 (0.849, 0.912)^a
Pop. density quintile 3 dummy	0.145 (0.137, 0.154)^a	1.007 (0.973, 1.043)	0.626 (0.602, 0.650)^a
Pop. density quintile 4 dummy	0.096 (0.091, 0.103)^a	0.902 (0.869, 0.938)^a	0.485 (0.465, 0.506)^a
Pop. density quintile 5 dummy	0.070 (0.066, 0.077)^a	0.886 (0.852, 0.926)^a	0.413 (0.392, 0.433)^a
Any class 1 or 2 highway dummy	1.639 (1.593, 1.698)^a	0.905 (0.891, 0.919)^a	1.095 (1.072, 1.119)^a
Percent ZIP code instability	1.006 (1.002, 1.009)^a	1.001 (0.999, 1.004)	1.005 (1.002, 1.008)^a
Intercept	4.232 (3.797, 5.092)^a	0.364 (0.317, 0.498)^a	0.497 (0.418, 0.556)^a
SD (CAR random effect)	0.708 (0.682, 0.731)	0.224 (0.211, 0.235)	0.217 (0.202, 0.233)
SD (non-CAR random effect)	0.644 (0.629, 0.657)	0.098 (0.079, 0.113)	0.202 (0.187, 0.216)
CAR proportion of error variance	0.548 (0.521, 0.572)	0.841 (0.782, 0.896)	0.535 (0.471, 0.602)
Moran’s I for CAR random effect	0.434 (Z = 28.097)	0.774 (Z = 50.075)	0.451 (Z = 29.227)
Deviance (−2^a LogLikelihood)	111,210	74,539	67,309

Notes: Posterior results are from Bayesian space-time Poisson analyses of 1600+ California ZIP codes over the years 1999–2008 (total n = 16,712). Each Poisson model included an exposure variable with coefficient restricted to one, calculated on the assumption that outcome counts study-wide are distributed in exact proportion to population (total crash model) or to total crashes (HBD and SVN crashes models). Raw Poisson coefficients and credible intervals have been exponentiated and are thus interpretable as relative risks.

Well-supported effects (those for which the 95% credible interval does not include a relative risk of one).