zia wadud
University of Leeds, Institute for Transport Studies, Faculty Member
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The introduction of connected and automated vehicles (CAVs) has the potential to bring numerous advantages to urban mobility. However, many challenges for road infrastructure need to be overcome before those benefits can be achieved. This... more
The introduction of connected and automated vehicles (CAVs) has the potential to bring numerous advantages to urban mobility. However, many challenges for road infrastructure need to be overcome before those benefits can be achieved. This study addressed multiple dimensions of the implications of CAV deployment for road infrastructure through a comprehensive survey with 168 experts from different sectors and regions around the world. The issues are grouped into five categories: (1) key challenges of accommodating CAVs in existing urban transport networks; (2) infrastructure improvement required for shared CAV models; (3) maintenance aspects of infrastructure for CAVs; (4) implementation time of infrastructure support for CAVs; and (5) financing infrastructure upgrades to facilitate CAVs on the roads. The outcomes of the research show that there is still no consensus among the stakeholders on what should be considered to maximise CAV benefits for society as a whole. This indicates the necessity for cooperation between stakeholders to achieve the safe and efficient operation of CAVs. Overall, this study provides in‐depth insights for decision‐makers and transport planners to form policies, regulations, and guidelines regarding the future implementation of CAVs for roads before their commercialisation phase.
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The use of bicycles is substantially affected by the daily and hourly weather pattern, which is set to change due to climate change. It is therefore important to understand the potential changes in order to accommodate adaptation planning... more
The use of bicycles is substantially affected by the daily and hourly weather pattern, which is set to change due to climate change. It is therefore important to understand the potential changes in order to accommodate adaptation planning for cycling. The authors propose a framework to model the potential changes in bicycle flow in London by developing a negative binomial count-data model and by incorporating future projected weather data from downscaled global climate models, a first such approach in this area. High temporal resolution (hourly) of the model allows the authors to decipher changes not only on an annual basis, but also on a seasonal and daily basis. The authors find that there will be a modest 0.5% increase in the average annual hourly bicycle flows in London's network in 2041 over year 2011. The increase is primarily driven by a higher temperature due to a changed climate, although the increase is tempered due to a higher rainfall in the future. The annual average masks the differences of impacts between seasons though - bicycle flows are expected to increase during the summer and winter months (by 1.6%), decrease during the spring (by 2%) and remain nearly unchanged during the autumn. Leisure cycling will be more affected by a changed climate, with an increase of around 7% during the weekend and holiday cycle flows in the summer months.
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The cost index (CI) is a tool that is growing in importance for airlines. It works by balancing the costs of time with the cost of fuel to determine the speed of a flight. Slower speeds result in fuel cost savings but higher... more
The cost index (CI) is a tool that is growing in importance for airlines. It works by balancing the costs of time with the cost of fuel to determine the speed of a flight. Slower speeds result in fuel cost savings but higher time-dependent costs and faster flights vice versa. With the cost of fuel rising and climate change issues surrounding air travel increasing the need for efficiency, the CI needs to be optimised. However, in general airlines find the calculation of CI challenging, particularly regarding extra costs owing to delay and cumulative maintenance and crew costs. The aim of this paper is to present a new way of calculating CI values on a flight-to-flight basis through the optimised cost index (OCI) model. Instead of constraining all costs to the traditional CI equation, the OCI model uses additional alternative calculations to take all costs into account fully. The OCI model provides an accessible and transparent way of calculating optimum CI values for airlines through a simple interface. In the future the model can also be used to assess the impact of future policies on a flight-to-flight basis, adding extra value to the OCI model.
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The fuel demand literature generally focuses on the determination of a single long run or short run price and income elasticity of gasoline for a given country. However, a single elasticity may not dissect the distributional burden faced... more
The fuel demand literature generally focuses on the determination of a single long run or short run price and income elasticity of gasoline for a given country. However, a single elasticity may not dissect the distributional burden faced by different socio-economic groups when faced with a fuel tax or a carbon trading policy (for climate mitigation). Different responses to the same change in price or income are likely to occur, depending on their travel needs, which in turn is contingent upon their income, location of residence and other factors, such as levels of vehicle ownership. This paper investigates the differences in gasoline demand elasticities for different income quintiles. Group-wise aggregated consumer expenditure data for 20 years is used to derive elasticity estimates for the United States. Results show that the elasticities vary for different income quintiles and follow a U-pattern from the lowest to the highest income quintile. The lowest income quintile is found to have the largest price elasticity. The lowest and the highest income quintile appear to be statistically insensitive to any changes in income. The rebound effect also follows the U pattern, with the highest rebound observed among the wealthiest households. Rural households appear to have lower price elasticity than households in urban areas.
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The COVID-19 pandemic has affected many daily activities, primarily as a result of the perceived contagion risk and government restrictions to mitigate the spread of the virus. To this end, drastic changes in the trip choices for... more
The COVID-19 pandemic has affected many daily activities, primarily as a result of the perceived contagion risk and government restrictions to mitigate the spread of the virus. To this end, drastic changes in the trip choices for commuting to work have been reported and studied, mostly through descriptive analysis. On the other hand, modeling-based research that can simultaneously understand both changes in mode choice and its frequency at an individual level has not been much used in existing studies. As such, this study aims to understand the changes in mode-choice preference and the frequency of trips, comparing pre-COVID with during-COVID scenarios, in two different countries of the Global South: Colombia and India. A hybrid multiple discrete-continuous nested extreme value model was implemented using the data obtained from online surveys in Colombia and India during the early COVID-19 period of March and April 2020. This study found that, in both countries, utility related to a...
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Transport plays a major role in spreading contagious diseases such as COVID-19 by facilitating social contacts. The standard response to fighting COVID-19 in most countries has been imposing a lockdown—including on the transport sector—to... more
Transport plays a major role in spreading contagious diseases such as COVID-19 by facilitating social contacts. The standard response to fighting COVID-19 in most countries has been imposing a lockdown—including on the transport sector—to slow down the spread. Though the Government of Bangladesh also imposed a lockdown quite early, it was forced to relax the lockdown for economic reasons. This motivates this study to assess the interaction between various non-pharmaceutical intervention (NPI) policies and transport sector outcomes, such as mobility and accidents, in Bangladesh. The study explores the effect of NPIs on both intra- and inter-regional mobility. Intra-regional mobility is captured using Google mobility reports which provide information about the number of visitors at different activity locations. Inter-regional, or long-distance, mobility is captured using vehicle count information from toll booths on a major bridge. Modeling shows that, in most cases, the policy interv...
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This paper measures ‘excess’ car travel for its role in decarbonisation. On average, each English adult travels around 5,680 miles a year and emits 1,006 kg of CO2. However, the top 5% ‘excess’ car users travel 4.8 times and emit 5.7... more
This paper measures ‘excess’ car travel for its role in decarbonisation. On average, each English adult travels around 5,680 miles a year and emits 1,006 kg of CO2. However, the top 5% ‘excess’ car users travel 4.8 times and emit 5.7 times the national average. Four binary logistic regression analyses were used to model the probability that people with specified characteristics belong to the ‘excess’ mileage and emitter groups. Results indicated that gender, employment and socio-economic status, household income (higher quintiles), company car availability, residential location and local population density were highly significant correlates of this ‘excess’ travel mileage. Multiple car ownership, business travel by car, multiple international flight frequencies and ownership of larger and diesel cars were positively associated with excess travel and emissions. A mileage rationing scheme targeting the top 20% users can cut emissions substantially (by 26%) compared to targeting ‘excess’ (top 5%) users only.
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Robotics and autonomous systems are reshaping the world, changing healthcare, food production and biodiversity management. While they will play a fundamental role in delivering the UN Sustainable Development Goals, associated... more
Robotics and autonomous systems are reshaping the world, changing healthcare, food production and biodiversity management. While they will play a fundamental role in delivering the UN Sustainable Development Goals, associated opportunities and threats are yet to be considered systematically. We report on a horizon scan evaluating robotics and autonomous systems impact on all Sustainable Development Goals, involving 102 experts from around the world. Robotics and autonomous systems are likely to transform how the Sustainable Development Goals are achieved, through replacing and supporting human activities, fostering innovation, enhancing remote access and improving monitoring. Emerging threats relate to reinforcing inequalities, exacerbating environmental change, diverting resources from tried-and-tested solutions and reducing freedom and privacy through inadequate governance. Although predicting future impacts of robotics and autonomous systems on the Sustainable Development Goals i...
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Fuel use in aviation is burdening the industry owing to its expense and worries about carbon dioxide emissions. With limited technological solutions for aircraft, small improvements in fuel efficiency are becoming increasingly important.... more
Fuel use in aviation is burdening the industry owing to its expense and worries about carbon dioxide emissions. With limited technological solutions for aircraft, small improvements in fuel efficiency are becoming increasingly important. Cost Index (CI) is a tool which controls the speed of an aircraft and therefore overall fuel use. Although the concept is simple, balancing fuel costs and time-dependent costs it is subject to misuse. This study aims to evaluate how the correct use of CI can affect fuel use and carbon emissions and assess the barriers and measures that are needed in finding the optimal CI value. A range of CI values are modelled for six different aircraft types to assess the difference in flight time and fuel use, before costs are modelled for a B767-300ER. Real aircraft data is used to validate results and provide an insight into the practical flight considerations that are required when using the CI. Results show that although changing CI values may only result in...
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A dominant mode of transmission for the respiratory disease COVID-19 is via airborne virus-carrying aerosols. As national lockdowns are lifted and people begin to travel once again, an assessment of the risk associated with different... more
A dominant mode of transmission for the respiratory disease COVID-19 is via airborne virus-carrying aerosols. As national lockdowns are lifted and people begin to travel once again, an assessment of the risk associated with different forms of public transportation is required. This paper assesses the risk of transmission in the context of a ride-sharing motorbike taxi—a popular choice of paratransit in South and South-East Asia and Sub-Saharan Africa. Fluid dynamics plays a significant role in understanding the fate of droplets ejected from a susceptible individual during a respiratory event, such as coughing. Numerical simulations are employed here using an Eulerian–Lagrangian approach for particles and the Reynolds-averaged Navier–Stokes method for the background air flow. The driver is assumed to be exhaling virus laden droplets, which are transported toward the passenger by the background flow. A single cough is simulated for particle sizes 1, 10, 50 μm, with motorbike speeds 1,...
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There is huge potential to link electric vehicles, local energy systems, and personal mobility in the city. By doing so we can improve air quality, tackle climate change, and grow new business models. Business model innovation is needed... more
There is huge potential to link electric vehicles, local energy systems, and personal mobility in the city. By doing so we can improve air quality, tackle climate change, and grow new business models. Business model innovation is needed because new technologies and engineering innovations are currently far ahead of the energy system’s ability to accommodate them. This report explores new business models that can work across the auto industry, transport infrastructure and energy systems.
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Stair is an important functional element of a building. Presently, helicoidal stairs are gaining popularity because of their attractive appearance. However, design of the helicoidal stair is quite difficult as the exact method of its... more
Stair is an important functional element of a building. Presently, helicoidal stairs are gaining popularity because of their attractive appearance. However, design of the helicoidal stair is quite difficult as the exact method of its analysis is very cumbersome. Due to the complex geometric configuration of this structure, the present methods of analysis are based on various idealizations and assumptions. Under this background, finite element approach has been applied to study the validity of the current methods in use. The study has been extended further to determine the stress resultants of the helicoidal stair slab including an intermediate landing for the development of a simplified design process. The investigation has lead to a number of findings. Firstly, the existing methods of helicoidal stair slab analysis have been found to vary a little with the finite element analysis. The possibility of suggesting temperature and shrinkage steel for the design of the Ree helicoidal sla...
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This paper provides a spatial comparison of the carbon dioxide (mean grams of CO2 per kilometre) and the nitrogen oxide (mean grams of NOx per kilometre) emissions factors of the car fleets registered across the local authorities of the... more
This paper provides a spatial comparison of the carbon dioxide (mean grams of CO2 per kilometre) and the nitrogen oxide (mean grams of NOx per kilometre) emissions factors of the car fleets registered across the local authorities of the United Kingdom as of 2014. These metrics are derived from the New European Driving Cycle test procedure and provide an indication of the global and local pollution profiles of the local car stock. Exploratory spatial analysis indicates that these emission factors exhibit a substantial geographical variation across the local authorities, suggesting that some local car fleets are dirtier or cleaner than others. Spatial autocorrelation analysis indicates that a significant degree of spatial organisation in these emission factors is present, with a number of hot-spots and cold-spots identified. Interestingly, these emission factors are uncorrelated with one another, suggesting that they represent separate perspectives on the environmental sustainability ...
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Help or hindrance? Implications of fully automated vehicles by Dr. Zia Wadud, University of Leeds on Thursday, May 30, 2019
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Although several studies have attempted to determine the mileage and time inefficiency of ridesourcing services due to concerns about traffic and environmental impacts of these services, all of them provide a point estimate, which does... more
Although several studies have attempted to determine the mileage and time inefficiency of ridesourcing services due to concerns about traffic and environmental impacts of these services, all of them provide a point estimate, which does not reflect the uncertainties in the calculation of these estimates. As such this study aims to present the efficiencies as ranges, based on lower and upper limits by identifying drivers' daily activity schedule. Based on an analysis of 200 busiest RideAustin drivers’ trips data (around 282,037 trips over a 6 months period from 1 October 2016) the study finds that the mileage efficiency ranges from 44.3% to 71.6%, while time efficiency ranges from 42.8% to 58.4%. This means that for every 100-miles of a fare-payer passenger, drivers must travel an additional 40 to 126 miles empty. The heterogeneity of the efficiency at the driver level and the efficiency in the temporal dimension were also considered
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This article explores a tension between financialisation of electricity infrastructures and efforts to bring critical urban systems into common ownership. Focusing on the emerging landscape of electricity regulation and e-mobility in the... more
This article explores a tension between financialisation of electricity infrastructures and efforts to bring critical urban systems into common ownership. Focusing on the emerging landscape of electricity regulation and e-mobility in the United Kingdom (UK), it examines how electricity grid ownership has become financialised, and why the economic assumptions that enabled this financialisation are being called into question. New technologies, such as smart electricity meters and electric vehicles, provide cities with new tools to tackle poor air quality and greenhouse gas emissions. Electricity grids are key enabling infrastructures but the companies that run them do not get rewarded for improving air quality or tackling climate change. UK government regulation of electricity grids both enables financialisation and forecloses opportunities to manage the infrastructure for wider environmental and public benefit. Nonetheless, the addition of smart devices to this network – the ‘smart g...