According to the ADR Agreement, road tunnels should be assigned a specific tunnel category regarding the passage of dangerous goods. The categorization shall be based on examining the dangers of explosion, release of toxic gas or volatile toxic liquid and fires, which may cause numerous victims or serious damage to the tunnel structure. EU Tunnel Directive 2004/54/EC aims to ensure a minimum level of safety for users in road tunnels in the Trans-European Road Network. EU member states are required to develop, at national level, their own detailed methodology for tunnel risk assessment. Different risk models exist in the literature, however in many European countries the QRAM (Quantitative Risk Assessment Model) is the one most widely used and can satisfy the regulatory framework for tunnel categorization. In this paper, a methodological approach has been presented using the QRAM for determining optimum tunnel categorization according to ADR Agreement requirements.