5 resultados para National Research Council (U.S.). Highway Research Board
em Universidad Politécnica de Madrid
Resumo:
Spain has a long tradition of encouraging toll highways by granting concessions to private companies. Concessions in Spain have been characterized by a willingness to transfer considerable risk to the private sector. Traffic demand, acquisition of the right-of-way, and financial risk have often been allocated to the private sector. From 1996 to 2011, 16 toll highway concessions, covering a total distance of 835 km, were awarded by the central government of Spain with this approach. Some of those highways started their operations just before the economic recession began. The recession had negative consequences for Spain's economy. The gross domestic product per capita plummeted, and the unemployment rate increased from 9% to 20% of the working population in just 2 years. The recession also had severe consequences for the economic performance of toll highway concessions. Traffic levels declined at a much greater rate than did the gross domestic product. In addition, the conditions imposed by the financial markets on borrowers became much stricter because of the liquidity crisis. This study analyzes the impact that the economic recession ultimately had on the performance of toll highway concessions in Spain and the actions that the government adopted to avoid the bankruptcy of the concessionaires. It was found that the economic recession helped identify some deficiencies in how risk had been allocated in Spain. The measures that both Spain and the European Union are adopting so as to improve risk allocation are discussed.
Resumo:
The need of decarbonization of urban mobility is one of the main priorities for all countries to achieve greenhouse gas (GHG) emissions reduction targets. In general, the transport modes which have experienced the most growth in recent years tend to be the most polluting. Most efforts have been focused on the vehicle efficiency improvements and vehicle fleet renewal; nevertheless more emphasis should be placed on strategies related to the management of urban mobility and modal share. Research of individual travel which analyzes CO2 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. This paper explores the sustainability impacts of daily mobility in Spain using data from two National Travel Surveys (NTSs) (2000 and 2006) and includes a method by which to estimate the CO2 emissions associated with each journey and each surveyed individual. The results demonstrate that in the 2000 to 2006 period, there has been an increase in daily mobility which has led to a 17% increase in CO2 emissions. When 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 not only take the number of journeys into account but also consider distance. The contributions of this paper have potential applications in the assessment of current and future urban transport policies.
Resumo:
Transport climate change impacts have become a worldwide concern. The use of Intelligent Transport Systems (ITS) could contribute to a more effective use of resources in toll road networks. Management of toll plazas is central to the reduction of greenhouse gas (GHG) emissions, as it is there that bottlenecks and congestion occur. This study focuses on management strategies aimed at reducing climate change impacts of toll plazas by managing toll collection systems. These strategies are based on the use of different collection system technologies – Electronic Toll Collection (ETC) and Open Road Tolling (ORT) – and on queue management. The carbon footprint of various toll plazas is determined by a proposed integrated methodology which estimates the carbon dioxide (CO2) emissions of the different operational stages at toll plazas (deceleration, service time, acceleration, and queuing) for the different toll collection systems. To validate the methodology, two main-line toll plazas of a Spanish toll highway were evaluated. The findings reveal that the application of new technologies to toll collection systems is an effective management strategy from an environmental point of view. The case studies revealed that ORT systems lead to savings of up to 70% of CO2 emissions at toll plazas, while ETC systems save 20% comparing to the manual ones. Furthermore, queue management can offer a 16% emissions savings when queue time is reduced by 116 seconds. The integrated methodology provides an efficient environmental management tool for toll plazas. The use of new technologies is the future of the decarbonization of toll plazas.
Resumo:
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 (CO2) 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 CO2 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 CO2 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.
Resumo:
La vitamina E pertenece al grupo de nutrientes con capacidad reguladora del sistema inmune (Koutsos y Klasing, 2008). En aves, la vitamina E induce cambios tanto en el sistema inmune innato como en el específico, mejora la función fagocítica de los macrófagos, amortigua la respuesta en fase aguda, disminuye la proporción de heterófilos y potencia la síntesis de anticuerpos (Koutsos y Klasing, 2008; Khan et al., 2012). Recientemente se ha demostrado que parte del efecto de la vitamina E está ligado a su capacidad de actuar directamente sobre factores de transcripción nuclear que modulan la expresión de citoquinas, tales como el factor-Kappa B o el PPAR γ (Koutsos y Klasing, 2008; Nakamura y Omaye, 2009). Por otro lado, el impacto de la vitamina E sobre la modulación del sistema inmune viene definido por factores tales como la edad y la relación dosis-respuesta. En broiler la inclusión en la dieta de niveles moderadamente superiores (25-50 UI/kg dieta) al recomendado por el National Research Council (NRC, 1994; 10 UI/kg) aumenta los títulos de anticuerpos tras la vacunación (Friedman et al., 1998; Leshchinsky y Klasing, 2001; Lin y Chang, 2006). Sin embargo, niveles superiores a 150 UI/kg tienen un efecto supresor sobre la producción de anticuerpos (Koutsos y Klasing, 2008). En relación a la edad es importante determinar aquellos periodos o “ventanas” en los que es necesario estimular el sistema inmune (Kogut, 2009). Un periodo a considerar sería el de las dos primeras semanas de vida del pollo debido a la menor funcionalidad de macrófagos y heterófilos (Kogut, 2009). El presente trabajo tiene como objetivo evaluar el efecto del nivel de Vitamina E y la edad sobre la modulación de la respuesta inmune en pollos. Para ello se estudió el efecto de la inclusión de 40 y 160 ppm de vitamina E en la dieta sobre la expresión de la interleuquina 2 (IL 2), el interferón gamma (IFN γ) y el factor de crecimiento mielomonocítico (MGF) en el bazo de los animales a los 7 y 21 días de edad.