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.