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A linear elastic fracture mechanics method is proposed to investigate the fracture behavior of hot mix asphalt and warm mix asphalt; this method was used in this study to calculated the fracture toughness of hot mix asphalt and warm mix asphalt containing 3% Sasobit at low temperatures (0, − 10, and – 20 °C) and two types of bitumen (60/70 and 85/100). A semi-circular specimen with an edged crack under three-point bending load mode was used to create different loading modes, including pure mode I and pure mode II, to test the fracture toughness. The critical stress intensity factor was calculated using the critical load obtained from the failure test. The shape factor was determined from finite element analysis. The results show that hot mix asphalt has a higher fracture toughness against crack growth than the warm mix asphalt containing Sasobit. In addition, the fracture toughness of asphalt mixture with a penetration grade of 85/100 against crack growth is more than that of the mixture with a penetration grade of 60/70. The minimum fracture toughness of hot mix asphalt and warm mix asphalt occurred in pure mode I loading condition.

Horizontal curves as one of the most dangerous places on roads affect the vehicle's balance, which depends on various factors such as vehicle type and superelevation. Side friction, one of the most critical parameters in designing curves, ensures driver safety and comfort. Previous studies have not adequately addressed the specific safety characteristics and challenges of broken back curve as a type of horizontal curve, especially for different types of vehicles and superelevation modes. Therefore, in this research, the impact of superelevation changes on the side friction of broken back curves was investigated on rural highways. To examine the effects of various factors on vehicle dynamics, CarSim and TruckSim software were applied to simulate 378 scenarios. These scenarios included various road geometries, vehicles, curves, and speeds. The simulations were performed on three types of vehicles (E-class Sedan, E-class SUV, and two-axle conventional loaded truck). Finally, the multiple regression analysis was carried out to assess the impact of various parameters on the side friction factor. According to the results, the longitudinal grade, vehicle speed and curve radius significantly affected the side friction factor, so that -8% grade and lower amounts of speed and curve radius increased the side friction of the broken back curves. Sedans and SUVs in continuous and trucks in discontinuous superelevation change conditions experienced more side friction, which allowed drivers more control over the vehicle. The multiple regression analysis results of the side friction factor showed that the truck regression models had the highest R2values.

Moisture susceptibility is one of the most important distresses that affects the life of the flexible pavement. Various methods, such as adding the appropriate additive, have been proposed to improve the asphalt mix properties. Some of these additives have environmental, and some have economic characteristics. In this study, three additives were used to study the moisture susceptibility and rutting of Hot Mix Asphalt (HMA), including rubber powder (RP), Tire Reclaim (TR10), and Butyl Reclaimed (BR120). For this purpose, the Marshall Stability test, Marshall Ratio (for determining the rutting), and Indirect Tensile Strength (ITS) were performed on the samples. Also, the economic analysis of the additive's effects on HMA was evaluated. The results of the Marshall test showed that adding all three additives increased the Marshall Stability and the Marshall ratio. As a result, adding TR10 and BR120 improved the Marshall ratio or rutting more than rubber powder. Indirect tensile strength test results also showed that the addition of rubber powder and TR10 led to improved HMA performance against moisture susceptibility. However, the use of BR120 as an additive reduced HMA moisture susceptibility. On the other hand, the economic analysis showed that adding 20% of rubber powder and TR10 would make the project much more economical. Further, adding BR120 to the asphalt mix provided economic benefits in every percentage. Consequently, based on the presented arguments, adding 20% of rubber powder and TR10 for technical and economic reasons leads to the best result.

The most important objectives of the air transport fleet design are meeting the travel demand in the network of existing trajectories, reducing costs and improving the emission rate of environmental pollutants. The environmental performance of the airline fleet is considered as a basic criterion for the design of air transport systems because of concerns in the area of global warming. In this study, the emission rate of environmental pollutants is separately measured, and logical relationships among fuel consumption, the emission rate of propellants, the volume of travel demand by airline fleet, and flight travel time are determined through using an optimisation model based on system equilibrium conditions. Eventually, the optimisation problem presented in a systematic air transport network is analysed and the results indicate that the emission of environmental pollutants is reduced by 64%.