Fuel Consumption as a Spatial Proxy: Measuring Urban Infrastructure Performance in Juba, South Sudan

<title>Abstract</title> <p>Urban infrastructure performance in data-scarce cities is often difficult to evaluate using conventional transport and engineering datasets. This paper proposes vehicular fuel consumption per kilometer as a spatial friction proxy for assessing urban road infrastructure performance in Juba, South Sudan. Building on conventional Vehicle Kilometers Travelled (VKT) energy-intensity approaches, the study reframes fuel consumption not simply as a measure of vehicle efficiency, but as an indicator of infrastructural interruption and spatial resistance within the urban environment. Using a transect-based observational methodology, repeated runs were conducted across one inter-city corridor and three intra-city routes characterized by varying surface conditions and junction densities. A normalized fuel consumption (NFC) metric was calculated to compare spatial efficiency across routes. Results show that intra-city mobility consumed between 6.9 and 10 times more fuel per kilometer than inter-city highway travel despite significantly shorter distances and lower speeds. Routes with higher junction density, mixed surfaces, potholes, and marram conditions consistently recorded elevated NFC values. When translated into monetary cost, these inefficiencies reveal substantial hidden energy and economic burdens imposed on urban residents. The study demonstrates the potential of fuel consumption as a low-cost, scalable proxy for evaluating infrastructure performance and identifying high-friction urban corridors in rapidly growing, data-scarce cities.</p>