Determination and assessment of an effective commercial speed of bus lines on the road network of Sfax city, Tunisia

Abstract

Over the previous few decades, Sfax city has witnessed a huge urbanization movement pushing the city boundaries beyond agricultural areas. This has been accompanied by an enormous extension of its transport network to meet the city dwellers need for commuting to distant employment zones. The demand for mobility has therefore risen because of the combination of an increasing population and longer distances. The failure of the city public transport system led citizens to rely more and more on individual transportation means (80% vs 20% in 2012), which resulted in two major problems: traffic jams and pollution. To face this worsening situation, the authorities suggested the alternative of inserting a double-track tramway in special crossable areas and in the middle of its roads. However, sharing the traffic space between the tramway and the conventional means of transport may result in such problems as the lack of space and the negative impact of the neighboring traffic on the tram’s commercial speed making it impossible to reach 20 km/h. The current research attempted to determine the commercial speed based on the road network. Busses were used to carry out a commercial speed measure campaign during peak hours adopting the manual time recording approach. The obtained results show that the commercial speed on 13 lines varies between 10.2 and 18 km/h. On three ring roads, it varies between 8.8 and 23 km/h. The decrease of the commercial speed value may generate congested traffic. Sfax city had better opt for an elevated or underground railway network than a tram, which would make the situation worse.