Modeling and Maximum Likelihood Fitting of Gamma-Ray and Radio Light Curves of Millisecond Pulsars Detected with Fermi

Pulsed gamma rays have been detected with the Fermi Large Area Telescope (LAT) from more than 20 millisecond pulsars (MSPs), some of which were discovered in radio observations of bright, unassociated LAT sources. We have fit the radio and gamma-ray light curves of 19 LAT-detected MSPs in the context of geometric, outer-magnetospheric emission models assuming the retarded vacuum dipole magnetic field using a Markov chain Monte Carlo maximum likelihood technique. We find that, in many cases, the models are able to reproduce the observed light curves well and provide constraints on the viewing geometries that are in agreement with those from radio polarization measurements. Additionally, for some MSPs we constrain the altitudes of both the gamma-ray and radio emission regions. The best-fit magnetic inclination angles are found to cover a broader range than those of non-recycled gamma-ray pulsars.Comment: 4 pages, 3 figures, 2011 Fermi Symposium proceedings - eConf C110509 -- v2 corrects caption of Figure 1, v3 corrects missing fil

Financial implications of specifying service quality in public transport service contracts with a large captive user base – the case of South Africa

Improved service quality is increasingly acknowledged as critical for increased patronage of public transport services. However, in markets characterised by large proportions of captive public transport users, typically found in developing or emerging economies with low car ownerships rates, the marginal benefits of improved service quality are not apparent. The paper uses historical financial and patronage data from existing bus contracts in South Africa and a conjoint-analysis based behavioural model to estimate the budgetary implications, and marginal benefits, of specifying service quality in public transport contracts, where marginal benefits are defined in terms of nominal welfare benefits to society. It is shown that the marginal benefits of improved service are significant and may outweigh the marginal cost of improved service quality or the business as usual alternative. Practical implications of the findings on contract planning and designs are also discussed in the context of markets with characteristically large proportions of captive public transport users.Institute of Transport and Logistics Studies. Faculty of Economics and Business. The University of Sydne

Access envelopes: A new accessibility mapping technique for transport and settlement planning

The article describes the application of a GIS-based accessibility measurement technique suited to assessing the impact of both transport and spatial development strategies on the location-specific affordability of job access for poor households. The access envelope methodology extends existing accessibility measures by: explicitly accounting for public transport service patterns; including transport costs as a dimension of accessibility; and deriving a single intuitive measure of access reflecting the potential income earnable by a person living in a certain location, after paying for transport. Several case studies from the City of Tshwane are presented, illustrating its use for assessing spatial integration and transport initiatives. The cases demonstrate how Tshwane’s emerging Bus Rapid Transit (BRT) system selectively enhances accessibility to jobs, although its marginal accessibility benefit is reduced by the part-duplication of existing rail lines to core employment areas. While the BRT improves the net earning potential of low-income workers in certain areas, its ultimate benefits will significantly depend on its achievement of network effects – especially via the reduction of first/last-kilometer trip costs – and its ability to leverage higher density development within walking distance of the route. Accordingly, results obtained with the access-envelopes method carry significant implications for current transport planning in the main metro cities

Accessibility and Social Welfare: A study of the City of Johannesburg

Within the corpus of accessibility measures is the Net Wage After Commute which describes the potential wage earnable less the transport costs incurred to commute to work from a particular location. This paper explores the time-series developments of accessibility, using this poverty-relevant metric, in low-income residential areas of the City of Johannesburg, biennially from 2009 to 2013 when accessibility patterns were altered as a result of major investments in the Bus Rapid Transit (BRT) system. Furthermore, a difference-in-differences approach was adopted to explore the effects of access to the BRT on the well-being of lower-income households, investigating the premise that transport related benefits brought about by such investments translate to social welfare improvements. The results suggest that significant time-series changes in accessibility patterns are driven by affordability against the backdrop of decentralisation, particularly for low-income areas in the peripheries of the city. The difference-in-differences model reveals that the BRT did not improve the well-being of residents, however, likely users of the service are better off in terms of well-being than non-users. This suggests that that BRT in Johannesburg is beneficial as a transport project, but not as a general urban intervention able to improve the overall amenity of served communities.Institute of Transport and Logistics Studies. Faculty of Economics and Business. The University of Sydne