However, the minimum time headway, a relevant indicator of safe driving, did change while processing incoming information (F1,22) = 5.1, P < 0.034, while a significant interaction with traffic density (F 1,22) = 5.8, P < 0.024) indicates that only in the busy traffic condition minimum time headway increased, from.70 s to.93 s.
Though we found significant variability in traffic density across cohort homes, traffic varied somewhat less within residential neighborhoods than across the entire urban core, as shown in Figure 1.
A number of studies have reported significant associations between traffic density or proximity to roads and various respiratory symptoms in children (Brunekreef et al. 1997; Edwards et al. 1994; Venn et al. 2001).
With respect to the three different systems, no significant effect was found but traffic density did have a significant effect (F 2,21) = 7.3, P < 0.013) too.
Multiple regression analysis was conducted to show the significant effect of relative traffic density, transmission range, and market penetration on the robustness measure.
A test for trend with increasing quintiles of traffic was significant (p ≤0.05) for traffic density and current asthma.
In our final multivariate model (R2 = 0.32), the local influences of highways and arterial/collector roads were statistically significant, as were local traffic density and distance to the airport terminal (all p < 0.001).
For bronchitis, we observed associations for the 90th percentile, with traffic density being statistically significant.
Traffic density variables were statistically significant across all buffer sizes (100 m through 400 m).
Both outcomes were associated with high traffic density, but ORs were significant for gestational diabetes only.
Of four studies reporting statistically significant positive results, three used measures of traffic density (Crosignani et al. 2004; Nordlinder and Jarvholm 1997; Pearson et al. 2000), and one study examined residential distance from roadways (Knox 2006) to assess exposure.
