TDM strategies for reducing environmental impacts of road traffic in presence of unusual demand

The air pollution due to road traffic represents a real environmental emergency, in particular in urban and metropolitan areas with high population density. The admitted maximum values of air pollutants are frequently exceeded and therefore local administrations have to adopt measures based on limitations of vehicular circulation. Several epidemiologic studies have highlighted as the atmospheric pollution produces serious damages to the human health. In particular, the thin powders, or particular matter, (PM10) are considered one of more dangerous pollutants for the human health (van Gent and Rietvels, 1993; Danielis and Chiabai, 1998; Kelly, 2003; Nel, 2005; Neidell, 2006). When in a zone of an urban area an important event occurs, the road traffic increases in a short time window producing congestion and environmental impacts. This paper studies some Travel Demand Management (TDM) strategies that can be adopted for limiting (and/or for redistributing) the road traffic in these cases, reducing road traffic emissions (as proposed by Gärling et al., 2002; Etyemezian et al., 2003; Loukopoulos et al., 2004; Concas and Winters, 2007; VTPI, 2009). After a literature review of 'general' TDM strategies, that can be adopted in urban areas for reducing private car use, the paper explores the possibility of applying these strategies in the occurrence of important events and proposes new innovative strategies that can be adopted in these particular cases. The proposed TDM strategies are tested and results concerning pollution are compared on a simplified network.