• Energy Research
• 12. Responsible consumption close
• 9. Industry and infrastructure close
• Transport Research close

When considering sustainability from a socioeconomic and environmental point, the South African public transport industry was not an integral part of such planning until the last decade. Various well-intended and well-defined public procurement and environmental regulatory policies and instruments were put in place over the years, however, they appear to be failing in achieving the goals of local job creation and alleviation of unemployment. This exploratory literature review study of various public documents, regulatory instruments, and review reports aims to evaluate current knowledge pertaining to the current level of sustainable transport from a life-cycle approach, in support of overall sustainable goals in South Africa. The research set out to assess the status of public procurement in the revitalising of public rail freight transport towards identifying areas of excellence that could be used to address under-performance in other areas. The documentary analysis found various areas where the public procurement policies within South Africa, which aims to promote local participation, are facing difficulties due to lack of access to modern technology as well as inadequate skills levels to be able to partake in the ventures. In exploring South African challenges and current solutions, the article recommends a holistic and integrated approach to provide for a sustained manufacturing and service supply stream within the local railway transport environment.

There is an ongoing interest in developing new alternative fuels (such as biofuel) for both aviation and road transport sectors to meet increasing energy demand and assist in reducing greenhouse gas (GHG) emissions. The major contribution of this work is to develop an aviation biofuel from a new feedstock and create the best possible biodiesel-diesel blends for the transport sector. This study focuses on improving engine performance and reducing emissions by enhancing combustion efficiency using these newly developed fuels without any modification of the modern engine. The combustion and emissions were closely monitored to evaluate the pollutants formation in a compression ignition (CI) engine. Better performing fuels were identified and their tribological behaviour was also studied to assess their impact on engine life.A wide range of biofuel feedstocks (over 150 species) was initially investigated to identify the most prospective feedstocks for producing biodiesels. The study eventually identified six prospective feedstocks namely Mandarin peel waste, Crambe, Tamanu, Borage, Waste Avocado flesh and Bush nut for biofuel production. The biofuels were produced in the laboratory from these selected feedstocks. The fatty acid methyl esters (FAMEs) composition and physio–chemical properties of these newly produced biofuels were evaluated using ASTM and EN standards.The fuel properties of these biodiesels revealed that the properties of the Mandarin biofuel closely fit with the properties of commercial jet fuel with a calorific value of 44.66 MJ/kg (4.3% higher than commercial jet fuel) and a higher flash point of 52 °C. This biofuel has a lower viscosity (about 2.13 mm2/s at minus 20 degree C.) which is desirable and is self–oxygenated and sulphur free. Therefore, it is seen as a prospective new source of aviation biofuel production which is a new finding. This has not been studied earlier.As an aviation engine was not available, Mandarin aviation biofuel was tested in a lean diesel engine and showed excellent performance and a large reduction in engine emissions. It can achieve reductions of up to 30.0% CO, about 33.5% HC and around 19.2% PM (particulate matter) at full load with variable speed and 33.0% CO, 32.8% HC, 28.5% PM emission reduction at variable load as compared to ultra – low – sulphur diesel (ULSD) by blending 20% with fossil fuel.Other biodiesel (Crambe, Tamanu, Borage, Avocado, Bush nut) blends (B5 to B20) were also tested in a four stroke diesel engine to evaluate the performance and emission parameters at different operating and load conditions. The results revealed that Avocado biodiesel shows overall better performance (about 0.50% less BP, 0.83% more BSFC, and 0.18% less BTE as compared to ULSD at full load and rated speed) compared to other fuels. However, Crambe, Borage, and Bush nut also show close performance with Avocado biodiesel. Blending up to 20% of this biodiesel can reduce emissions by up to about 50% CO, 27% HC and 36% PM, however it increases NOx emission by about 26% compared to ULSD at full load and rated speed. On the other hand, Tamanu biodiesel blends show poor engine performance though emission reduction is comparable with other biodiesels at the same operating conditions.For further improvement in engine performance and emission reduction this study developed four mixture blends by combining two biodiesels (totalling 5% at different proportions) and paraffin as an additive at 4% with the remaining 91% being ULSD. The mixture blends are described as ManCr_Pa (Mandarin-Crambe_Paraffin), TaMan_Pa (Tamanu-Mandarin_Paraffin), BoMan_Pa (Borage-Mandarin_Paraffin) and AvBn_Pa (Avocado-Bush nut_Paraffin). The mixture blends show improved performance compared to each B5 blend and significantly reduce emissions like B20 blends due to their improved fuel properties. Among these mixture blends, the Avocado-Bush nut and paraffin (AvBn_Pa) ternary mixture demonstrates comparable performance with ULSD. It reduces about 48.0% CO, 30.0% HC, 40.0% PM emissions compared to ULSD. This equates to about 16.0% CO, 8.7% HC and 28.0% PM more reduction of emissions compared to an Avocado B5 blend. This mixture blend produces about 9% less NOx compared to the B5 blend of Avocado biodiesel. On the other hand, the ManCr_Pa mixture blend reduces about 62% HC emission compared to ULSD with about 12% lower NOx emission. The advanced combustion analysis was done on the better performing blends (i.e. for ManCr_Pa and AvBn_Pa mixture blends) to evaluate pollutant formation mechanisms during combustion. The results revealed shorter ignition delay and longer combustion duration for AvBn_Pa. This blend also exhibits higher cylinder pressure and higher heat release rate with a longer duration of the diffusion combustion phase. Additionally, a knocking characteristic was identified for ManCr_Pa mixture blend. The tribological characteristics such as friction, wear, lubrication stability and metal surface morphology were also evaluated using high-resolution SEM/EDX microscopy to assess energy savings, engine reliability, and impacts on engine life. This study revealed an excellent tribological performance of AvBn_Pa blend compared to ULSD with about 21% less friction coefficient at steady state condition, around 19% less wear scar diameter, higher lubrication film stability, as well as less wear debris and metal corrosion. The study concluded that AvBn_Pa blend is the best mixture blend in all aspects of performance considered, namely emission reduction, improved combustion and tribological behaviour for a sustainable environment as well as sustainable engine health for the transport sector. The study will provide useful information and guidelines to biofuel stakeholders, the transport sector, engine designers, the aviation industry and policy makers involved with newly developed aviation biofuels and other biodiesel usage in a full-scale diesel engine. It will provide new opportunities to future researchers to develop Mandarin aviation biofuel as a commercial aviation fuel. This research will help engine designers to develop more efficient and sustainable engines and to customise newly developed biodiesels for application in the transport sector.

Providing a sufficiently appropriate route environment is crucial to ensuring fair and safe biking, thus encouraging cycling as a sustainable mode of transport. At the same time, better understanding of cyclists’ preferences regarding the features of their routes and their infrastructure requirements is fundamental to evaluating improvement of the current infrastructure or the development of new infrastructure. The present study has two objectives. The first is to investigate cyclists’ route preferences by means of a choice experiment based on a stated preference survey. Subsequently, the second objective is to compare cyclist preferences in two countries with different cycling characteristics (both in infrastructure as well as cyclists’ behavior). For this purpose, a graphical online stated preferences survey was conducted in Greece and Germany. Within the framework of statistical analyses, multinomial mixed logit discrete choice models were developed that allow us to quantify the trade-offs of interest, while distinguishing between the preferences of different user groups. In addition, user requirements in Greece, as a country with a low cycling share and very little dedicated bike infrastructure, were compared to the requirements in Germany, where cycling is popular and the infrastructure is well developed. The results over the whole sample indicate that subgroups value infrastructure differently according to their specific needs. When looking at country specifics, users from Greece are significantly more willing to accept longer travel times in return for higher-quality facilities. The utility of low speed limits in mixed traffic is also different. In Germany, low speed limits offset the disturbance caused by motorized traffic, but in Greece they do not. Consequently, the results help to asses which types of infrastructure are most sustainable from a user perspective and help to set priorities when the aim is to adapt the road infrastructure efficiently in a stable strategy.

At present, the issue of public safety in the production and manipulation of hazardous chemicals deserves more attention, since various major accidents such as fires, explosions and toxic gas releases take place frequently. The issue of prevention of emergency events has become more and more topical. The growing amount of hazardous substances transported leads to increased risk of emergencies. In order to reduce this risk in the transport of hazardous substances, a number of technical, operational, traffic and safety conditions and requirements must be fulfilled. These all contribute to the reduction of hazards and risks. The aim of the presented article was to determine the extent of the danger zone in the event of a gasoline leak due to a traffic accident in a built-up urban area with a high frequency of traffic and population movement.

This research sets out to examine the interaction between accessibility, social inequalities and sustainability by revisiting a well-documented case of inequalities in access in Global South cities: Bogotá. Our analysis builds on the concept of accessibility, focusing on the role of transport as an enabler of opportunities for social interactions, healthcare and leisure, which are essential to the full participation in society. The research applies a methodological framework for accessibility developed and tested in the Latin American context, though it has not been previously applied to non-commuting travel. Our paper contributes to the existing evidence base showing the relevance of non-commuting travel to sustainable transport assessment in contexts of high inequality, which can be scaled up and applied in other contexts with various levels of social and environmental inequalities. The empirical analysis is based on data from Bogotá’s household travel survey. Using this dataset, we measure accessibility using a gravitational type of metric that is calibrated based on observed travel behavior. Accessibility levels were estimated by car and public transport for every zonal planning unit in the Bogotá Region. Accessibility indices are analyzed from an equity perspective using metrics such as the Palma ratio for differences of income and socioeconomic positions. Results show that on average, low- and middle-income areas have higher accessibility than high-income areas by both private and public transport. Accessibility conditions are discussed considering a framework of transitions to sustainable urban mobility, reflecting on various drivers and consequences of barriers to access in different areas and social groups. Our findings provide insights to support actions that redistribute accessibility of opportunities beyond the job market, questioning the applicability of accessibility measures to discuss equity and sustainability in cities such as Bogotá.

The “Avoid”, “Shift” and “Improve” (A-S-I) approach is an effective method for transforming an unsustainable transport system to a sustainable one. This study intends to examine the possible impact of the A-S-I policy measures in transforming the transportation system in Lagos - the most populous city and the commercial capital of Nigeria. The study employs the Long Range Energy Alternative Planning (LEAP) model to project future energy demand and greenhouse gas emissions to determine the most effective A-S-I option for the city. We construct a business-as-usual scenario for Lagos as well as sustainable road transport alternative policy scenarios. The results show that Lagos' biggest obstacle to achieving its emission reduction target is the presence of very old vehicles on its roads. Our analysis shows that emission reduction in the road transport sector in Lagos is sensitive to vehicle survivability rate (i.e. the fraction of vehicles of a certain age still driven). We conclude that unless the age limit of vehicles in Lagos reduces from 40 years to 22 years, vehicle growth rate from 5% to 2% and mileage by 2% per year from 2020 to 2032, Lagos may not achieve its target of 50% emission reduction by 2032.

The blending of hydrogen gas into natural gas pipelines is an effective way of achieving the goal of carbon neutrality. Due to the large differences in the calorific values of natural gas from different sources, the calorific value of natural gas after mixing with hydrogen may not meet the quality requirements of natural gas, and the quality of natural gas entering long-distance natural gas and urban gas pipelines also has different requirements. Therefore, it is necessary to study the effect of multiple gas sources and different pipe network types on the differences in the calorific values of natural gas following hydrogen admixing. In this regard, this study aimed to determine the quality requirements and proportions of hydrogen-mixed gas in natural gas pipelines at home and abroad, and systematically determined the quality requirements for natural gas entering both long-distance natural gas and urban gas pipelines in combination with national standards. Taking the real calorific values of the gas supply cycle of seven atmospheric sources as an example, the calorific and Wobbe Index values for different hydrogen admixture ratios in a one-year cycle were calculated. The results showed that under the requirement of natural gas interchangeability, there were great differences in the proportions of natural gas mixed with hydrogen from different gas sources. When determining the proportion of hydrogen mixed with natural gas, both the factors of different gas sources and the factors of the gas supply cycle should be considered.

Starting from the relationship between urban planning and mobility management, TeMA has gradually expanded the view of the covered topics, always following a rigorous scientific in-depth analysis. This section of the Journal, Review Notes, is a continuous update about emerging topics concerning relationships among urban planning, mobility and environment thanks to a collection of short scientific papers written by young researchers. The Review Notes are made up of five parts. Each section examines a specific aspect of the broader information storage within the main interests of the TeMA Journal. In particular: The Town Planning International Rules and Legislation Overview section aims at presenting the latest updates in the territorial and urban legislative sphere. The Covid-19 pandemic is causing a major impact on energy systems. Improving the energy efficiency of urban areas is now the cornerstone of scientific community and the European Commission discussions. Thus, the content of this review note aims at carrying out an analysis of the latest documents of the European Commission before and during the slow recovery from Covid-19 with the aim of identifying the priorities and areas on which to intervene to reduce energy consumption in different territorial contexts. TeMA - Journal of Land Use, Mobility and Environment, Vol 14 No 1 (2021): The city challenges and external agents. Methods, tools and best practices