**1. Introduction**

According to data from the National Confederation of Transport (http://www.cnt.org.br/), in Brazil about 61% of cargo and 95% of passengers are transported via highways, indicating that this transportation sector is economically relevant at the national scale, handling a substantial amount of financial resources [1]. Despite the recognized importance of highways for the country's economic development, road transport involves a diversity of cargo types, including dangerous products, which renders this activity a preoccupying risk of environmental and social impacts. The risk associated to the transport of a dangerous product depends not only on the substance being transported but also on the road network characteristics, weather conditions, driver skills and population concentration along the selected routes [2]. The potential impacts of accidents related to road transport of hazardous products were discussed in various studies, which triggered social concerns and were helpful as guides to the conception and implementation of adequate corrective and preventive actions [3]. However, before implementation of any specific measure, a correct diagnosis on vulnerability and risk is required.

The Multi Criteria Analysis (MCA) method embedded in a geographic information system (GIS), also known as Spatial MCA, is a computational tool that can assist the preparation of vulnerability and risk maps for decision making on the planning and operation road transport networks [4–6], as well as in many other environmental applications [7–12]. In the study of [5] MCA was used to determine the vulnerability of soil and water resources in rural basins, while in the study of [6] it was used to model the environmental risk of accidents involving the transport of dangerous products based on static and dynamic data. The work group of Van [13] developed a method to evaluate statistical data on road accidents involving dangerous products, from which it was possible to generate a global risk map. Regardless the method on which the vulnerability, the risk or the hazards are assessed, from a safety standpoint road risk managemen<sup>t</sup> requires the implementation of methods that are capable to provide a quick diagnosis on the potential environmental impact of an accident involving the spill and leaching of dangerous substances from a road. The challenge is therefore to develop and validate robust but expeditious diagnostic tools. The resort to statistical data on road accidents demands a significant time span dedicated to monitoring, while the generation of vulnerability maps cannot stand alone as method to identify the risky areas [2]. According to [14], besides the potential lack of reliable numbers the managemen<sup>t</sup> of road transport risk based on statistical data requires the capability to evaluate, in a short period of time, the diversity of transported materials, and the possible environmental consequences related to their road spill. This evaluation becomes even more complex given the multiplicity of road accident circumstances. The route to follow is therefore to combine hazard assessments (road accident counts) with vulnerability assessments at site and catchment scales.

The main purpose of this study is to combine a method already used to determine the environmental vulnerability of areas adjacent roads to spills of dangerous products [15] with road accident data, in a manner that becomes possible to analyze the accident scenario immediately after the occurrence and thus to implement an alert system whereby corrective measures can readily be triggered, such as the sending of resources, isolation of a certain area, withdrawal of the population, protection of springs, soil or water decontamination, among others.
