Traffic congestion poses a significant problem in urban areas globally, and yet no measure of congestion is universally applied. Various studies have evaluated congestion measures, however, none have identified and demonstrated a best-practice congestion metric that can compare congestion between road segments, networks, and city zones. Furthermore, no studies have proven the link between a congestion metric and traffic flow, despite suggestion by Lomax et al. in their seminal 1997 Quantifying Congestion report that an appropriate congestion metric should vary predictably according to flow. This paper aims to address these gaps in traffic congestion literature. Various congestion measures are evaluated according to standard criteria. Although this process has been followed before, this paper adds a unique criterion that requires congestion to be quantifiable from commercial floating car data (FCD), due to its extensive availability and relative affordability. The most appropriate congestion measure is evaluated to be the speed reduction index (SRI). The application of the SRI to describe spatiotemporal congestion patterns and flow dependency is then demonstrated in a case-study analysis in South Africa. This analysis exploited traffic impacts of the COVID-19 pandemic in 2020 (particularly, the stepwise increase from severely reduced traffic flows as lockdown levels eased), to evaluate SRI. The wide range of flows enabled an unprecedented regression analysis comparing congestion level and flow. The results of the regression analysis are highly significant ( p < 0.001) indicating that SRI-based congestion measurement tracks flow variation. This study further identified that unidirectional congestion, quantified by the SRI, is impacted by high bi-directional flow along arterials. These findings confirm the appropriateness of the SRI quantified from commercial FCD to measure congestion.
Fast-food drive-throughs are a common feature in our fast-paced lives where convenience and service access are highly prized. This convenience comes at a high environmental price: long queues of idling vehicles guzzle fuel and generate emissions linked to global warming and health concerns. Drivethroughs also generate significant income for franchisees and reduce parking requirements at fast-food outlets. Fast-food and drive-throughs are becoming more prevalent in the developing world at a time when these countries are facing rapidly increasing traffic congestion, driven by a desire for private transport use. This study considers aspects of sustainability of drive-throughs according to the mobility paradigm in the developing world, where vehiclecentric urban form and rapid development are contributing to a mobility crisis. The drive-through is a prime example of capitalist vehicle-centric urban form. This paper is intended as a starting point for discussion on drive-through appropriateness in developing countries. Only two aspects of drive-through operations are considered in this initial investigation: the cost of using a drivethrough (fuel cost and environmental cost, approximated by the emissions load), and the space saving benefit realized by eliminating parking. This research found that drive-throughs save substantial land area by reducing parking and stimulate higher profits, making it unlikely that drive-throughs will be phased out, even with the significant environmental impact of drivethroughs quantified in this paper. Recommendations for improved operations of drive-throughs are therefore suggested to mitigate long idling times in drive-through queues, and a call for more sustainable land-use planning is proposed.
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