On the calibration of the gravity model

Knowledge of Origin-Destination (OD) trip matrices is needed in many stages of transport planning. As direct observations of OD-flows are usually not available, a commonly used approach is to estimate them from traffic counts and other aggregated flow constraints. The under-specification that characterizes this estimation process can be resolved by requiring that OD-values conform to a model of travel demand. In this paper we consider a class of methods based on the gravity model, with either an exponential or a piecewise constant deterrence function. We focus on numerical methods to calibrate these models from traffic counts and establish a unifying analysis of them. The paper starts with a description of the gravity model, and a summary of the assumed modelling and observation error structures. Subsequently a likelihood expression is established which we seek to maximise. The paper then concentrates on methods that can be used for this purpose. Existing methods are discussed, and it is shown that some of the difficulties that occur when applying them can be resolved by a change of variables to logarithms of the model parameters. A key result concerns the matrix of second derivatives of the likelihood function. This result is then applied and leads to a new optimisation method. In a series of experiments this method is shown to be robust and computationally efficient

White Gold : Opportunities for Dairy Sector Development Collaboration in East Africa

A study of the dairy sector in six East African countries was followed by a dairy expert consultation in Uganda in April 2014. The objective of the initiative was to explore possibilities to improve coordination among development agencies, investors and other value chain stakeholders and governments, and for creating synergy within and between the different countries. This report describes outcomes of both study and consultation and is intended to serve as a reference document for all stakeholders. It includes recommendations and priority actions that should enable stakeholders to capitalize on the opportunities in the East African dairy sector and clarify the roles of various partners in this endeavour (donors, public sector, and private sector). Study and consultation were initiated by the Inter-Agency Donor Group (IADG) on pro-poor livestock research and development. Report CDI-14-00

A realist process evaluation within the Facilitating Implementation of Research Evidence (FIRE) cluster randomised controlled international trial: An exemplar

Trial Registration: Current Controlled Trials ISRCTN11598502Background Facilitation is a promising implementation intervention, which requires theory informed evaluation. This paper presents an exemplar of a multi-country realist process evaluation that was embedded in the first international randomised controlled trial evaluating two types of facilitation for implementing urinary continence care recommendations. We aimed to uncover what worked (and did not work), for whom, how, why and in what circumstances during the process of implementing the facilitation interventions in practice. Methods This realist process evaluation included theory formulation, theory testing and refining. Data were collected in 24 care home sites across four European countries. Data were collected over four time-points using multiple qualitative methods: observation (372 hours), interviews with staff (n=357), residents (n=152), next of kin (n=109) other stakeholders (n=128), supplemented by facilitator activity logs. A combined inductive and deductive data analysis process focused on realist theory refinement and testing. Results The content and approach of the two facilitation programmes prompted variable opportunities to align and realign support with the needs and expectations of facilitators and homes. This influenced their level of confidence in fulfilling the facilitator role, and ability to deliver the intervention as planned. The success of intervention implementation was largely dependent on whether sites prioritised their involvement in both the study and the facilitation programme. In contexts where the study was prioritised (including release of resources) and where managers and staff support was sustained, this prompted collective engagement (as an attitude and action). Internal facilitators’ (IF) personal characteristics and abilities, including personal and formal authority, in combination with a supportive environment prompted by managers triggered the potential for learning over time. Learning over time resulted in a sense of confidence and personal growth, and enactment of the facilitation role, which resulted in practice changes. Conclusion The scale and multi-country nature of this study provided a novel context to conduct one of the few trial embedded realist informed process evaluations. In addition to providing an explanatory account of implementation processes, a conceptual platform for future facilitation research is presented. Finally a realist informed process evaluation framework is outlined, which could inform future research of this nature.The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 223646. The funder had no role in designing, conducting, or interpreting study findings.https://implementationscience.biomedcentral.com/articles13pubpub13

Latent variables and route choice behavior

In the last decade, a broad array of disciplines has shown a general interest in enhancing discrete choice models by considering the incorporation of psychological factors affecting decision making. This paper provides insight into the comprehension of the determinants of route choice behavior by proposing and estimating a hybrid model that integrates latent variable and route choice models. Data contain information about latent variable indicators and chosen routes of travelers driving regularly from home to work in an urban network. Choice sets include alternative routes generated with a branch and bound algorithm. A hybrid model consists of measurement equations, which relate latent variables to measurement indicators and utilities to choice indicators, and structural equations, which link travelers' observable characteristics to latent variables and explanatory variables to utilities. Estimation results illustrate that considering latent variables (i.e., memory, habit, familiarity, spatial ability, time saving skills) alongside traditional variables (e.g., travel time, distance, congestion level) enriches the comprehension of route choice behavior

Geschiedenis Der Doopsgezinden in Nederland

Amsterdam263 p.; 23 c

White Gold : Opportunities for Dairy Sector Development Collaboration in East Africa

A study of the dairy sector in six East African countries was followed by a dairy expert consultation in Uganda in April 2014. The objective of the initiative was to explore possibilities to improve coordination among development agencies, investors and other value chain stakeholders and governments, and for creating synergy within and between the different countries. This report describes outcomes of both study and consultation and is intended to serve as a reference document for all stakeholders. It includes recommendations and priority actions that should enable stakeholders to capitalize on the opportunities in the East African dairy sector and clarify the roles of various partners in this endeavour (donors, public sector, and private sector). Study and consultation were initiated by the Inter-Agency Donor Group (IADG) on pro-poor livestock research and development. Report CDI-14-00

Traffic monitoring using handheld GSM phones. Part B: Simulation results

Report published by the the University of Technology Delft, commissioned by Syntrack. This report contains the description of a novel map-matching algorithm, and the results of a simulation study into the feasibility of traffic monitoring using handheld mobile phones.Transport & PlanningCivil Engineering and Geoscience