Developing a Sustainable Urban Mobility Index: Methodological Steps

Introduction

The world’s population is increasingly city-based. In 2014, the urban population accounted for 54% of the total global population, up from 30% in 1950, and is expected to reach 67% by 2050 (United Nations, 2014). This explosion in urban population has been accompanied by a massive growth in both passenger and freight transport. Today, 64% of all travel undertaken is within urban environments and the total number of urban kilometers travelled is expected to triple by 2050 (van Audenhove, Korniichuk, Dauby, & Pourbaix, 2014). Urban mobility has become a crucial component of modernity, and has generated a revolution in contemporary economic and social relations. However, rapid growth of urban mobility systems has also presented a big challenge to all major city authorities around the world, that is, how to enhance mobility while at the same time reducing congestion, accidents, and pollution (Camagni, Gibelli, & Rigamonti, 2002; Mihyeon Jeon, & Amekudzi, 2005). Taking the European Union (EU) as an example, a large majority of European citizens live in an urban environment, with over 60% living in urban areas of over 10,000 inhabitants. As a consequence, congestion in the EU is often located in and around urban areas and costs nearly 100 billion Euro, or 1% of the EU GDP, annually. Moreover, urban mobility in the EU accounts for 40% of all CO₂ emissions of road transport and up to 70% of other pollutants from transport (European Commission, 2015). Under this circumstance, the European Commission proposed in its Action Plan on Urban Mobility of 2009 to accelerate the take-up of a Sustainable Urban Mobility Plan (SUMP) in Europe, which has the central goal of improving accessibility of urban areas and of providing high-quality and sustainable mobility and transport to, through and within the urban area (Wefering, Rupprecht, Buhrmann, & Bohler-Baedeker, 2014). In short, to preserve the liveability of urban environments, the mobility system needs to move towards sustainability. To this end, a thorough understanding and assessment of the current performance of the urban transport system is required (Black, Paez, & Suthanaya, 2002; Yigitcanlar, & Dur, 2010). However, because sustainability is a complex matter that is affected by numerous factors, no single indicator is capable of capturing the entire picture. Consequently, the development of a composite indicator (CI), which combines individual indicator values into an overall index score, is considered to be a valuable approach for evaluating urban mobility sustainability (Mori, & Christodoulou, 2012).

Theoretically, a CI is a mathematical aggregation of a set of individual indicators that usually has no common units of measurement. The main pros and cons of using CIs are summarized in Saisana & Tarantola (2002) and the Organization for Economic Co-operation and Development (2008). For instance, CIs enable users to compare complex realities effectively and are easier to interpret than trying to find a common trend in many separate indicators. However, they may also invite simplistic policy conclusions or be misused to support a desired policy. In general, “… it is hard to imagine that debate on the use of composite indicators will ever be settled…” (Saisana, Tarantola, & Saltelli, 2005). However, if the methodological process for creating an index is scientifically sound, transparent, and based on solid statistical and conceptual principles, then the construction of a CI over a set of indicators is worthwhile. The index can be utilized as a powerful tool for policy analysis and public communication (Shen, Hermans, Bao, Brijs, Wets, & Wang, 2015).