Abstract
The environmental impact assessment (EIA) is an acknowledged method in the world used for estimating the possible changes to the environment caused by proposed development activities, including the development of linear infrastructures. The EIA of planned projects for building or reconstruction of the motorways in Latvia are usually carried out in a short time frame, and therefore the data characterizing current environmental conditions sometimes are not of the best quality. These kind of data gaps cause an inaccurate prognoses on the possible changes to environmental quality after project implementation. Our research demonstrates that this was the case concerning the weak evaluation of sound levels on the Saulkrasti bypass. Within the framework of the EIA, the prognosis of sound levels was elaborated, prooving that, generally, the traffic sound will be within the officially permissible levels, although the problem points are recognized and the erection of sound barriers are proposed. After construction of bypass, however, the noise monitoring has not been carried out in order to verify whether the prognosis are true. In fact, the results of experimental measurements at four points on the Saulkrasti bypass showed the opposite - the noise level in the daytime (Ld) exceeded the acceptable value at all points of the measurements, including the places with installed sound barriers. The task of our experimental measurements on the bypass was also to find a correlation between the noise level and traffic intensity. The results showed that a correlation between these factors is weak, and the noise level is not directly dependant on traffic intensity, but on the total impact of several factors.