There are several factors that can cause the high level in noise exposure such as the type of engines, exhaust systems and tires interacting with the road. Generally the factors which influence the traffic noise are divided in four categories. Figure 5: Factors affecting Traffic-Noise The first category consist of traffic parameters such as the speed, density, composition, (one way street) driver’s behavior and traffic fluidity. As the population increases, the traffic volume arises gradually. Figure 6: Graph of Volume against Time Image by Pervasive The volume increases year by year. According to the analysis of the above graph the volume roughly increasing by 60% per year. The second category consists of the road parameters such as the road design (tunnels, cuts, enbankments), the gradients, degree of curvature, as well as the nature and width of road surface. If the road pavement consists of stone then an increased noise level will be generated. Figure 4: Type of road surface The graph below shows the sound pressure level for different types of vehicles in different pavement type. It is shown that the vehicles travelling on an Open Graded Asphalting Concrete (OGAC) and on Portland Cement Concrete (PCC) generate high sound pressure level. The third category consists of the environmental parameter such as the distance and height from the road of the recipient of noise, the condition of ground between the road and point of intersection, the reflection of noise from buildings along the road and the presence of natural screening. Figure 5: The presence of natural screening on roads Image by John Grayson The last category is the weather parameters such as the direction, speed of the wind and the weather conditions such as the rain, snow and dry condition.