Meteorology today : An introduction to weather, Climate, and the environment

A relationship between people’s mobility and their social networks is presented based on an analysis of calling and mobility traces for one year of anonymized call detail records of over one million mobile phone users in Portugal. We find that about 80% of places visited are within just 20 km of their nearest (geographical) social ties’ locations. This figure rises to 90% at a ‘geo-social radius’ of 45 km. In terms of their travel scope, people are geographically closer to their weak ties than strong ties. Specifically, they are 15% more likely to be at some distance away from their weak ties than strong ties. The likelihood of being at some distance from social ties increases with the population density, and the rates of increase are higher for shorter geo-social radii. In addition, we find that area population density is indicative of geo-social radius where denser areas imply shorter radii. For example, in urban areas such as Lisbon and Porto, the geo-social radius is approximately 7 km and this increases to approximately 15 km for less densely populated areas such as Parades and Santa Maria da Feira.

Socio-geography of Human Mobility: A study using longitudinal mobile phone data

Ever growing populations in cities are associated with a major increase in road vehicles and air pollution. The overall high levels of urban air pollution have been shown to be of a significant risk to city dwellers. However, the impacts of very high but temporally and spatially restricted pollution, and thus exposure, are still poorly understood. Conventional approaches to air quality monitoring are based on networks of static and sparse measurement stations. However, these are prohibitively expensive to capture tempo-spatial heterogeneity and identify pollution hotspots, which is required for the development of robust real-time strategies for exposure control. Current progress in developing low-cost micro-scale sensing technology is radically changing the conventional approach to allow real-time information in a capillary form. But the question remains whether there is value in the less accurate data they generate. This article illustrates the drivers behind current rises in the use of low-cost sensors for air pollution management in cities, whilst addressing the major challenges for their effective implementation.

The rise of low-cost sensing for managing air pollution in cities

In most large cities, the taxi industry is subject to various types of regulation, such as entry restrictions and price controls, and economists have examined the economic consequences of such regulation extensively. Unfortunately, in conventional economic analyses of competition and regulation in the taxi industry little attention has been paid to one important issue: congestion externalities due to both occupied and vacant taxi movements together with normal vehicular traffic. This study investigates the nature of equilibrium and regulation in the taxi market by taking account of congestion externalities and adopting a realistic distance-based and delay-based taxi fare structure. The monopoly, the social optimum and the stable competitive solutions are examined and illustrated with a numerical example.

Regulating Taxi Services in the Presence of Congestion Externality

A factor that influences transit ridership but has not received much attention is weather. This paper examines the effects of weather on bus ridership in Pierce County, Washington for the years 2006-2008. Separate ordinary least squares regression models were estimated for each season, as weather conditions may have different effects depending on the time of year. Four weather variables were considered: wind, temperature, rain, and snow. High winds negatively affected ridership in winter, spring, and autumn. Cold temperatures led to decreases in ridership in winter. Rain negatively impacted ridership in all four seasons, and snow was associated with lower ridership in autumn and winter. These results suggest that adverse weather conditions can have a negative effect on transit ridership.

Marco Veloso

Papers

Analisys of taxi data for understanding urban dynamics