Erodibility of soils in rural roads

Rainfall is a significant factor in the erosion of unpaved roads. If inappropriate soils are used for construction, even a short rainfall duration can render poor conditions on unpaved roads. Rainfall has a twofold effect on the surface. The impact of raindrops can result in the dislodgement of soil particles; while subsequent water flow transports the loosened soils. A laboratory investigation was undertaken to study erodibility of granular and clayey soils that may be used for the construction of unpaved roads. The study aimed at identifying the suitability of soils that can be used for the construction of erosion resistant unpaved roads. Those roads are indispensable for sustainable growth of rural areas in developing countries. Compacted samples were subjected to simulated rainfall intensities of 30 mm/hr, 51 mm/hr and 68 mm/hr for 30 minutes over a two-day period. The eroded soil quantities contained in the run-off were measured at intervals of 5 minutes. The effect of erosion on the surface particles was assessed using photographs. Erodibility decreased with increases of both the clay fraction and the size of the granular particles. Moreover, erodibility increased with the increases of the rainfall intensity, slope gradient and length. Smaller particles eroded faster than coarser particles. At the surface, the number of soil particles reduced, whilst their size increased with the increasing rainfall duration. The runoff coefficients increased with the increasing clay content, slope gradient, and higher rainfall intensity. Both the erodibility and the runoff coefficients reduced in the second-day experiments

Evidence on Impact Evaluation of Road Transport Networks using Network Theory

The development of network theory has resulted in a growing understanding of the topological properties of transport networks. This has led to knowledge on how network indicators relate to the performance of a network, their wider socio-economic impacts and insights about how networks can best be extended. It has also provided transport planners with an insight into traffic flow, travel demand, centrality and connectivity of transport networks. This rapid evidence-review summarises literature (1999-2019) that have used network theory to evaluate the impact evaluation of road networks, it also presents the technological advancements in network theory. The identified studies outline the beneficial impacts of road networks on the economy, how connectivity can be improved to improve network resilience, reliability, performance and reduce maintenance costs. A number of studies describe how networks can be designed to reduce the impact on the environment. However, with the exception of only three studies i.e Kumar and Kumar (1999), Vasas and Magura et al. (2009) and Walker et al. (2013), the impacts are not quantified. The magnitude of the impact, for a particular network, is a function of the type of model used. As studies could not be found where different models have been used to assess similar impacts, it was not possible to compare numerically the impacts of different model types. Enhancements to network theory have focused on (i) developing new measures and indicators to assess connectivity, vulnerability and economic impact of transport networks, (ii) applying weightages to nodes and links to evaluate economic and ecological impacts and (iii) developing multiple layers within the network models for better spatial analysis. Recent studies have also expanded network theory and integrated it with risk modelling and probabilistic methodologies to identify vulnerable or critical elements within a given transport network

Investigating the Effectiveness of Fourier Transform Infrared Spectroscopy (FTIR) as an Antifraud Approach for Modified Epoxy Asphalt Mixes in Developing Countries

The road surfacing material is continuously exposed to both traffic and climate stresses, including extreme temperatures and heavy rainfalls. Subsequently, most road defects start from the surface and potentially develop into road structural damage. Appropriate road maintenance schemes are necessary to ensure the surface remains functionable. On the other hand, these maintenance schemes would be uneconomical without the use of durable and climate-resilient materials for road surfacing. This is vital in low-income countries (LICs), where the burdens of road maintenance are economically unbearable. In this regard, long-life epoxy-modified asphalt offers an opportunity to achieve durable and climate-resilient pavement surfacing. However, epoxy is an expensive material that may be subject to fraud, leading to poor quality of the surfacing mixture and the resulting road infrastructure. In order to prevent fraud and ensure the quality of epoxy bitumen mixtures for road surfacing, Fourier transform infrared spectroscopy (FTIR) was used to characterise mixes of epoxy-modified bitumen and trace the content of epoxy. The findings showed that the epoxy content used in the preparation of mixes agreed with the epoxy content traced using FTIR. The mean difference between the two quantities was approximately ±1.0% with a correlation coefficient R2 > 0.9. Therefore, FTIR can efficiently provide an antifraud method for modified epoxy asphalt mixes at the plant level to help achieve sustainable pavements

Rainfall induced erosion of soils used in earth roads

Earth roads in rural areas of the developing world are key engines to the development of countries. They give access to education and health services, sustain agriculture and businesses, and promote social interactions between communities. However, earth roads suffer substantially from poor engineering and funding for construction and maintenance. Rainfall is probably their most dangerous enemy resulting in soil particle detachment leading to the loss of surface material. A laboratory rainfall simulator was used to identify the performance of an earth road surface compacted at the maximum dry density against rainfall energy and surface flow. Under the rain intensity of 30mm/hr, erosion increased with rain duration from 0 to 30 minutes. Fine sand (0.06 – 0.02mm) and medium sand (0.02 – 0.6mm) particles eroded faster than coarse sand (0.6 – 2mm) and gravel (> 2mm) particles of the sediments collected at 5 minutes intervals of time. Additionally, a 20cm x 20cm photograph at the same place was analysed using ImageJ software and showed reduction in number of particles from 18554 at 10 min to 5803 at 25 min as smaller particles had eroded in the meantime

Assessing social equity and accessibility of transport systems for people with disability in Kenya

Social equity can be associated with all road practices and policies that ensure fair and just transport in terms of mobility, access and costs allocated to the transport infrastructure. Equally, social accessibility reflects the attribute of transportation infrastructure and systems that enables affordable and accessible mobility for different users’ context. The implementation of these two aspects could be challenging in transport systems, particularly in the low- and middle-income countries (LMICs) due to the limitations associated with costs and policing. In this paper, we assess social equity and social accessibility provided to people with disabilities (PWDs) in transport systems of Nairobi, Kenya. To achieve this, a mixed-method approach was employed, comprising three set of data collection: (a) a systematic literature review of the current practices was undertaken, (b) a set of questionnaires involving roads authorities and service providers; and (c) Key-informant-interviews (KIIs) with decision makers in road and transport authorities, service providers and bus designers and manufacturers, as well as with PWDs associations and NGOs advocating for fair and inclusive transport. The study assessed current practices and challenges in transport of PWDs, with the aim of informing relevant stakeholders in a planned workshop. The findings show that social equity and accessibility provided to PWDs in transport systems of Nairobi could be improved significantly. The systematic literature shows that challenges faced by PWDs in transport systems of Kenya are less known, with limited rigorous research around the topic. Data collected from the questionnaires highlight that good policies are available at the level of public institutions, but these policies have not been fully implemented. Finally, findings from the KIIs indicate that there is palpable lack of coordination on programmes that should improve inclusivity in the Kenyan transport systems and alleviate the heavy burden on the PWDs shoulders