Transport is one of the main air pollution sources in urban contexts. Road characteristics, such as gradient, speed control devices, among others, have a great influence on transport emissions but this relationship is not yet fully understood. Studies have been focused on fuel consumption as an indirect indicator of potential emission of sector, more than analysis of specific contaminants emitted. This fact is particularly important for toxic pollutants such as polycyclic aromatic hydrocarbons (PAHs), which is due, in part, to difficulties associated with their capture/analysis in the atmosphere. Some bio-monitors, e.g., lichens, are becoming a reliable alternative for the sampling process, due to their flexibility and low-cost attributes. The present work analyses the ability of tropical lichens for providing an indication on the effect that traffic patterns and geometric design features (traffic activity, road gradient, traffic control devices and vehicular speed) of roads have on PAHs concentration emission. The PAHs associated to lichens showed a strong correlation with the gradient of the road (Spearman correlation p<0.005, with R=0.98). Additionally, the PAHs presented a trend coherent with the vehicle speed profile and the road green environment. Results indicated that influence of traffic patterns, road characteristics on PAH emissions may be efficiently detected by lichen biomonitoring techniques, just like carcinogenic equivalence sum (KE).