Management of urban mobility to control climate change in cities in

motorized modes are favored over other forms of transport, road transportation is the main energy consumption mode and, consequently, the main transportation pollutant source at 80% of the total transport energy demand (4). Passenger emissions are rising more rapidly than freight transport emissions, caused by an overall increase in daily mobility. These numbers put into perspective the need to set specific emissions targets for passenger mobility and to develop policies aimed at cohesive and concrete emissions reductions in passenger transport (5). Local mobility is important, because 40% of all transport-related CO 2 is emitted in cities. The need to decarbonize urban mobility is a priority if countries are to achieve reduction targets for GHG emissions. Moreover, the car is the main mode: 75% of all kilometers traveled (passenger kilometers) in European urban areas are produced by car journeys (6). The public transport mode share is decreasing almost everywhere and now accounts for only 16% of journeys (6). To achieve reduction targets for GHG emissions, more emphasis must be placed on modal split policies that highlight public transport and nonmotorized transport as viable options. For instance, Lapillonne et al. report that public transport is four times more energy-efficient than cars (7). Moreover, where rail infrastructures and bus lanes are available, public transport can compete with cars because of its efficiency and the fact that travel times during peak hours tend to favor public transport users. Overall, public transport offers a better level of service, mainly because of its regularity and reduced travel times. A shift is required in both travel behavior and the perception of public transport as an unsafe, time-consuming, inconvenient option among populations accustomed to traveling by car (8). A European Union white paper sets challenging targets for a shift to more sustainable modes in urban transportation in European countries, encouraging cities to increase the modal share of nonmotorized modes (9). Modal shift policies are consistently among the best practices in urban areas for reducing the environmental effects of urban transport. Rail modes are seen as an ecological form of transportation (10). Buses offer flexibility, can be used quickly in response to changing demand, and do not need specialized infrastructure, unlike trains (11). Walking and cycling are carbonless, environmentally friendly solutions for individual urban transport (12). In Europe, cycling and walking account for approximately 13% of urban passenger kilometers (13). In Spain, motorized modes are favored over other forms of transport, and much investment is made in new road infrastructure in dense urban areas. Moreover, Spanish daily commute patterns indicate that the population is slowly reverting from public transport to carbon-intensive automobile transport (5). However, the difference in the use of public transport in large and small urban areas is significant. In dense cities, travelers are more likely to use public transport; in Madrid, Barcelona, and Bizkaia, 20% to 30% of trips involve public transport, whereas the share of public transport is 5% to 11% in small urban areas. Notably, a significant percentage (30% to 45%) of daily journeys in Spain are made on foot (14). Management of Urban Mobility to Control Climate Change in Cities in Spain Natalia Sobrino and Andres Monzon The need to decarbonize urban mobility is one of the main motivations for all countries to achieve reduction targets for greenhouse gas (GHG) emissions. In general, the transport modes that have experienced the most growth in recent years tend to be the most polluting. Most efforts have focused on improvements in vehicle efficiency and on the renewal of vehicle fleets; more emphasis should be placed on strategies related to the management of urban mobility and modal share. Research of individual travel that analyzes carbon dioxide (CO 2 ) emissions and car and public transport share in daily mobility will enable better assessments of the potential of urban mobility measures introduced to limit GHG emissions produced by transport in cities. The climate change impacts of daily mobility in Spain are explored with data from two national travel surveys in 2000 and 2006, and a method for estimating the CO 2 emissions associated with each journey and each surveyed individual is provided. The results demonstrate that from 2000 to 2006, daily mobility has increased and has led to a 17% increase in CO 2 emissions. When these results are separated by transport mode, cars prove to be the main contributor to that increase, followed by public transport. More focus should be directed toward modal shift strategies, which take into account not only the number of journeys but also the distance traveled. These contributions have potential applications in the assessment of current and future urban transport policies related to low-carbon urban transportation