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Effect of rainfall on function service quality deterioration of dark roadways and its implication for stopping sight distance.

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Driving in the rain at night is challenging and more so if the roadway has no light. This study aims to ascertain whether rainy dark roadways would have significant influence on functional service quality reduction, and also the associated stopping sight distance implications for road users. Dark roadways are prevalent in Nigeria mainly because of poor energy management and the absence of long term sustained-energy strategic plans. The objectives are to determine the functional service quality in the presence of rainy dark roadways and compare with that taken on dry dark roadways. To that effect a rainy dark roadway impact study was carried out at four (4) selected sites in Nigeria for a period of eight (8) weeks. Based on the circumstances prevalent at the time of the survey, the study assumed that density was a result of speed and flow hence not directly affected by rainfall. This implies that functional service quality was fully the result of speed and travel time changes. Functional service quality describes the assessment of service delivery of roadways based on both road provider (travel speed) and user (travel time) perceptions. Vehicle types, volumes, speeds and rainfall were collected continuously at each surveyed road section for eight weeks and the results analysed. Traffic volume was converted into flow using modified passenger car equivalents values. The results of the analysis show reduction in travel speed with ensuing increase in travel time. Results show that the average travel time increased by 27.1 percent on dark roadways due to night rainfall. Results show that the average travel speed decreased by 18.7 percent on dark roadways due to night rainfall. The results from the analysis were used to establish the stopping sight distance implications of rainy dark roadways for motorists. Results show that on dark roadways the average stopping sight distance (SSD) increased by 25.8 percent due to rainy night. Results from the predicted travel time loss confirm the established evidence that travel time is a significant guide for measuring road effectiveness. Finally, since there is the potential to improve functional service quality output based on efficient and appropriate energy on one hand; effective management of resources on the other, the study concluded that in the presence of rainfall, dark roadways have a significant impact on the functional quality of service and stopping sight distance.


Doctoral Degree. University of KwaZulu-Natal, Durban.