Doctoral Degrees (Civil Engineering)

Permanent URI for this collection

https://scholar.sun.ac.za/handle/10019.1/764

Browse

Browsing Doctoral Degrees (Civil Engineering) by Author "Bruwer, Megan Melissa"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    The application of commercial floating car data for speed-based traffic state evaluation in the Sub-Saharan African context
    (Stellenbosch : Stellenbosch University, 2023-03) Bruwer, Megan Melissa; Andersen, Simen Johann; Walker, Ian; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: Floating car data (FCD) are traffic data that are passively reported from within the traffic stream by GPSenabled probe devices commonly carried in vehicles, including smartphones, on-board navigation devices, and vehicle tracking systems. Commercial FCD are collected, aggregated, stored, and sold by third-party traffic data entities, providing network-wide speed, travel time, and origin-destination data. Commercial FCD eliminate the need for traffic sensors and communications networks, while simultaneously reducing the data analysis demands typical of Big Data because commercial FCD are characteristically made available in structured and readily usable formats. Commercial FCD are poised to become a primary source of traffic data in low- and middle-income countries where traditional, sensor-based traffic data are only sparsely collected over a vast road network, thereby leapfrogging the extensive traffic data collection systems established in high-income countries. Presently, commercial FCD are not widely used or researched in Sub-Saharan Africa. This dissertation is, therefore, well timed in its aim to assess the correct application of commercial FCD in the Sub-Saharan African context. This dissertation identified that the sample providing commercial FCD results in an inherent bias (called sample bias) because the reporting devices are purchased according to socioeconomic status, particularly in Sub-Saharan Africa, where average income, smartphone penetration and technology uptake is low. This dissertation represents the first time that the term sample bias has been described and systematically investigated as a characteristic of commercial FCD. The research found that commercial FCD are impacted by sample bias according to the socioeconomic, demographic, and geographic distribution of the sample that reports FCD in Sub-Saharan Africa. Sample bias was also proven to impact the accuracy of FCD speeds to the extent that speed accuracy differed between cities in South Africa and between commercial FCD sources. Mathematical models for the correct application of FCD in Sub-Saharan Africa that can be applied irrespective of sample bias, were then considered. Sample bias can be excluded in congestion measurement using ratio indices. FCD were found to enable accurate and comparative congestion measurement, both of recurrent and non-recurrent congestion, using variations of the Speed Reduction Index. Finally, three unique use-case studies, specifically applicable to Sub-Saharan Africa, were carried out to demonstrate the usefulness of FCD to evaluate the impact of roadworks projects, identify potholes along rural routes, and map changes in traffic patterns during the COVID-19 pandemic. The primary contribution of this research will be to steer Sub-Saharan Africa towards applicable use-cases of commercial FCD for transport planning purposes. This dissertation should allow commercial FCD to be applied with confidence for the correct use-cases in Sub-Saharan Africa. This research has provided a guideline for the evaluation of potential sample bias and the impact thereof, demonstrated the huge potential for FCD-based traffic pattern monitoring in a Sub-Saharan African context – for both urban and rural applications – and suggested future research for continued Sub-Saharan-specific FCD application. This research is critical to guide commercial FCD towards a significant role in providing primary traffic data over the extensive road network of our continent.