A good quality road network is utmost important for the economic development of a country. In that context, countries pay more attention on building new road network or upgrading the existing road structure. However, this consumes energy and the hypothesis remains is that whether the rider comfort increases with embodied energy of the road structure. If the rider comfort deteriorates prior to design life, it is not sustainable. Thus, this research has the objective of finding the relationship between energy consumption of road construction and rider comfort level. In addition, assess the best range of energy level to get the optimum level of rider comfort. For this a sample of five newly constructed roads in Sri Lanka was selected. Sri Lanka, the island located in the Indian Ocean, is rebuilding its nation after 30 years long civil war and given the priority in developing the road network. Government spends millions of rupees without having any idea on the performance of the road surface with time.
Energy needed for road construction can be clustered as embodied energy in road construction materials consumed, embodied energy in the fuel consumed in road construction equipments, energy burn by workers, and energy for auxiliary activities (e.g., electricity for lighting). However, in this research only first two energy categories were considered since latter are difficult to be measured. The quantity summary sheets, BOQ details, fuel consumption reconciliation for machinery, cross sectional drawings of the road, etc were used to extract the quantity of material and amount of fuel used. By using calorific values (MJ/kg) and average specific gravity values of all the materials and fuel types, total energy consumed rate or embodied energy per unit area of the road was calculated.
The rider comfort of the road surface was related to International Roughness Index (IRI) which is defined as longitudinal unevenness of the road surface. Merlin- Model A 1460 was used to calculate the IRI for the selected road surfaces. The variation between energy consumption rate and IRI shows a logarithmic variation with R2 of 0.72. The accuracy of the developed model is assessed using RMS Error. With observing the trend of the model, it can be concluded that threshold level of 49 × 103 MJ/m2 will give an IRI value of 3 mm/m which is in the acceptable range (1.5–3.5 mm/m) according to Sayers et al. (1986). Thus the developed model is applicable in controlling the energy usage in road construction in order to obtain a good rider comfort level.
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