**3. Materials and Methods**

The method to investigate road accident scenarios based on the assessment of environmental vulnerability and road accident data related to transport of hazardous substances is illustrated in Figure 2 in the form of a workflow. The Multi Criteria Analysis represented in this diagram and used to assess environmental vulnerability has been developed and presented in the previous work of [15]. The coupling of those results with road accident data is performed in this study. The method developed in the earlier work of Machado and co-authors is briefly described in Section 3.1. The complement related to analysis of road accident data is described in detail in Sections 3.2 and 3.3. Both methods were implemented in Geographic Information System (GIS), frequently used in environmental studies [22–34]. In the present study, the specific GIS was IDRISI Selva software [35] that resorted to various sources of digital information, mostly public institution websites (e.g., http://www.webmapit. com.br/inpe/topodata/ for topographic data or https://earthexplorer.usgs.gov/ for land use/land occupation data). The full inventory of information sources is listed in [15].

**Figure 2.** Flowchart illustrating how contamination risk has been assessed in the present study, associated with spills of hazardous substances following a road accident.
