Traffic congestion is a global issue, which occurs during rush hour but also in situations of emergency causing massive congestion. This paper proposes a method for building a weighted road network by using the real-time traffic situation and the inherent characteristics of Urban Road Networks (URNs). To research the cascading failure vulnerability of URNs three kinds of node importance indexes are constructed from the structure, function, and traffic flow characteristics. Then the feasibility and validity of the proposed model are verified by taking Shanghai road networks (SRNs) as an example. The results indicate that the highest betweenness node-based attack causes the most damage to the SRNS of different types of attacks, and the SRNS cascade fails with the greatest speed and scale. Furthermore, we explore that the correlations between network vulnerability indicators, and suggest significant differences at different times during cascading failures of the weighted road network.