All descriptive computations and statistical analyses were
made using SPSS software (version 11.0; SPSS Inc., Chicago, IL,
USA). ANOVA with Bonferroni test at 95% significance was
used to compare concentrations between different commut-
ing modes. Independent t-tests were used to compare the
concentrations inside and outside vehicles. Two-tail paired t-
tests were used to compare concentrations between normal
operation and special events. Linear regression models were
used to analyze the relationship between personal exposure
concentrations and fixed-site monitoring concentrations.