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Leif Sörensen

Bio: Leif Sörensen is an academic researcher from Max Planck Society. The author has contributed to research in topics: Population & Revenue. The author has an hindex of 2, co-authored 7 publications receiving 16 citations. Previous affiliations of Leif Sörensen include University of Göttingen & Dresden University of Technology.

Papers
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Journal ArticleDOI
TL;DR: In this article, a real-life, fully flexible and true door-to-door DRT experiment was conducted in the Oberharz region of Germany, where over a 6-month period around 38,000 trips took place in the region and the analysis of these trips showed that an unrestricted DRT service between three main centres (Goslar, Clausthal-Zellerfeld and Osterode) results in main travel axes between these cities while the more remote areas forfeit mobility to these centres of public service provision.

35 citations

Journal ArticleDOI
TL;DR: Using WHO’s TB and public infrastructure data, it is conservatively estimated that the symptomatic critical case rate is between 8 and 12% due to the interaction of COVID-19 and TB, for a TB population of 0.52% in South Africa.
Abstract: Tuberculosis (TB) is the 10th leading cause of death worldwide, and since 2007 it has been the main cause of death from a single infectious agent, ranking above HIV/AIDS. The current COVID-19 is a pandemic which caused many deaths around the world. The danger is not only a coinfection as observed for TB and HIV for a long time, but that both TB and SARS-CoV-2 affect the respiratory organs and thus potentiate their effect or accelerate the critical course. A key public health priority during the emergence of a novel pathogen is the estimation of the clinical need to assure adequate medical treatment. This requires a correct adjustment to the critical case detection rate and the prediction of possible scenarios based on known patterns. The African continent faces constraining preconditions in regard to healthcare capacities and social welfare which may hinder required countermeasures. However, given the high TB prevalence rates, COVID-19 may show a particular severe course in respective African countries, e.g. South Africa. Using WHO's TB and public infrastructure data, we conservatively estimate that the symptomatic critical case rate, which affects the healthcare system, is between 8 and 12% due to the interaction of COVID-19 and TB, for a TB population of 0.52% in South Africa. This TB prevalence leads to a significant increase in the peak load of critical cases of COVID-19 patients and potentially exceeds current healthcare capacities.

7 citations

Journal ArticleDOI
16 Jul 2021
TL;DR: In this paper, the effects of policy measures on the further course of the COVID-19 epidemic were analyzed from an epidemiological perspective using agent-based epidemic simulations, and the results indicated that measures that are either lifted too early or are too lenient have no sufficient mitigating effects on infection rates.
Abstract: COVID-19 has spread rapidly around the globe. While there has been a slow down of the spread in some countries, e.g., in China, the African continent is still at the beginning of a potentially wide spread of the virus. Owing to its economic strength and imbalances, South Africa is of particular relevance with regard to the drastic measures to prevent the spread of this novel coronavirus. In March 2020, South Africa imposed one of the most severe lockdowns worldwide and subsequently faced the number of infections slowing down considerably. In May 2020, this lockdown was partially relaxed and further easing of restrictions was envisaged. In July and August 2020, daily new infections peaked and declined subsequently. Lockdown measures were further relaxed. This study aims to assess the recent and upcoming measures from an epidemiological perspective. Agent-based epidemic simulations are used to depict the effects of policy measures on the further course of this epidemic. The results indicate that measures that are either lifted too early or are too lenient have no sufficient mitigating effects on infection rates. Consequently, continuous exponential infection growth rates or a second significant peak of infected people occur. These outcomes are likely to cause higher mortality rates once healthcare capacities are occupied and no longer capable to treat all severely and critically infected COVID-19 patients. In contrast, strict measures appear to be a suitable way to contain the virus. The simulations imply that the initial lockdown of 27 March 2020 was probably sufficient to slow the growth in the number of infections, but relaxing countermeasures might allow for a second severe outbreak of COVID-19 in our investigated simulation region of Nelson Mandela Bay Municipality.

4 citations

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the minibus taxi industry in South Africa based on data from Rustenburg, a mid-sized city, to gain valuable insights into the working behaviour of minibus taxi drivers by taking an evidence-based and data-based approach.
Abstract: For many emerging and developing countries, urbanization and demographic changes require a remodelling of transportation systems and networks. Paratransit, with its demand responsive characteristics of being fully flexible, often represents the backbone of the transport sector while being an informal and, therefore, fairly unorganised system with little knowledge about working routines of its workers. As an example, this paper analyses the minibus taxi industry in South Africa based on data from Rustenburg, a mid-sized city, to gain valuable insights into the working behaviour of minibus taxi drivers by taking an evidence-based and data-based approach. Therefore, the principle of reference-dependent preferences is applied to the data to investigate the labour supply choice of taxi drivers, since sheer profit maximization has proven inadequate for the analysis here. Results indicate, that working hours for South African minibus taxi drivers are likely to be in the 10–12 h bracket with a revenue-dependent additional hour accounting for the revenue performance of that day. As a main finding however, South African minibus taxi drivers cannot clearly be attributed to either reference dependence or profit-maximization behaviour.

2 citations

Journal ArticleDOI
TL;DR: In this article, the authors examined the effect of two different compensation schemes on driver behavior in Kigali using survey data from 2019 and found that drivers who are compensated by performance are more likely to alter their behavior, responding to the incentive scheme through several channels.
Abstract: The rapidly growing city of Kigali has a bus network that is undergoing increased development as underlined in its Transport Master Plan. Two schemes of bus driver remuneration coexist in the city: One constitutes a hybrid salary and commission system, while the other pays a fixed monthly salary. This paper examines the effect of these differing compensation schemes on driver behavior in Kigali using survey data from 2019. The analysis applies linear models incorporating various aspects of driver behavior in a principal-agent framework. The results indicate that the performance-based compensation scheme is associated with higher per-trip passenger fluctuation and faster driving (possibly due to drivers aiming to accrue a higher income) compared to the fixed-wage system. Policy implications comprise the inclusion of further criteria in incentive contracts to internalize potential negative externalities on society, e.g., to hinder the endangerment of passenger safety by appropriately incentivizing drivers. In conclusion, bus drivers who are compensated by performance are more likely to alter their behavior, responding to the incentive scheme through several channels.

2 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article , the authors estimated age-specific and all-age IFR by matching seroprevalence surveys to total COVID-19 mortality rates in a population.

106 citations

Journal ArticleDOI
TL;DR: This paper presents the design of such a system in which users might be requested online to walk towards/from nearby pick-up/drop-off points if this improves overall efficiency, and provides a general formulation and specific heuristics that are able to solve it over large instances.
Abstract: On-demand systems in which passengers with similar routes can share a vehicle are expected to become a relevant part of future mobility, thanks to their flexibility and their potential impact on reducing congestion. Nevertheless, due to the long detours required by a door-to-door scheme, they induce extra costs to the users in terms of delay. In this paper, we face the design of such a system in which users might be requested online to walk towards/from nearby pick-up/drop-off points if this improves overall efficiency. We show theoretically that the general problem becomes more complex (as it contains two sub-problems that extend set-cover), analyze the trade-offs that emerge, and provide a general formulation and specific heuristics that are able to solve it over large instances. We test this formulation over a real dataset of Manhattan taxi trips (9970 requests during one hour), finding that (a) average walks of about one minute can reduce the number of rejections in more than 80% and Vehicles-Hour-Traveled in more than 10%, (b) users who depart or arrive at the most demanded areas are more likely to be required to walk, and (c) the performance improvement of the service is larger when the system receives more trip requests.

52 citations

01 Jan 2017
TL;DR: In this article, the authors present characteristics of rural areas for MaaS development, based on a project co-funded by the Ministry of Agriculture and Forestry of Finland, as well as goals and vision.
Abstract: This paper presents characteristics of rural areas for MaaS development, based on a project co-funded by the Ministry of Agriculture and Forestry of Finland. The paper presents rural mobility SWOT analysis and challenges, as well as goals and vision. Solutions for MaaS services in terms of collaboration, services & markets, planning & decision-making, and technology & information are proposed. The next steps to be taken in rural MaaS development are examined. Rural areas have challenges to organize mobility services due to long distances and narrow flows of people and material, as well as tightening financial targets. Rural areas have also a major potential to organize transport services more efficiently. The collaboration of different stakeholders — businesses, the public sector and people — is key to the success. New pilots with impact assessment should be carried out and best practices disseminated. The unique characteristics of rural areas should be taken into account in e.g. legislation and financing. Technology is an enabler of efficient MaaS services; thus digitalization of data and use of open/defined interfaces is recommended. A toolkit for MaaS pilot/service development is needed to promote the development and implementation of new MaaS services.

48 citations

Journal ArticleDOI
TL;DR: In this article , Malawian healthcare workers' (HCWs) COVID-19 vaccination and its hypothesized determinants were studied and adjusted multivariable logistic regression models were explored to explore how "what people think and feel" constructs were associated with HCWs' motivation to be vaccinated.

25 citations