Brakes are one of the basic safety systems on a vehicle. During the operation of the vehicle, the brakes allow the vehicle to slow down, i.e., to adapt to traffic conditions or to stop, if necessary. However, in all conditions mentioned, emissions of brake wear products occur, which are very harmful to the environment because they can contain heavy metals. Working parameters of braking process are responsible for the intensity of brake wear, which can be tested in laboratory or road conditions, as well as by using modern software packages. This paper covers the basic theoretical assumptions about brake wear, as well as the materials applied in their production. The methodologies that other authors have come up with in their research are shown in this paper. Those methodologies are related to testing the brake wear, the parameters which are the most influential on wear, as well as the measures for the reduction of brake wear. The available scientific literature in the subject area lead us to the conclusion what should be taken into the consideration in future research and what factors are not thoroughly investigated, all with the aim of reducing the emission of brake wear.

The braking system is one of the important systems from the aspect of vehicle safety, but it is also one of the systems that has a significant impact on the environment. Brakes are considered to be a source of non-exhaust particles, that is sources that create particles by the wear of the elements that are in contact with each other, and in this case, the brake friction elements (brake pads and rotating disc). Such particles often contain heavy metals that are part of the friction elements. There are a number of influencing factors that can affect the wear of the friction elements and increase the concentration of the formed particles. Laboratory methods of testing wear and particle formation, road tests and various simulations of brake wear are most often used for testing. In this paper, a review of methodologies for testing the formation of particles from the braking system, the materials used in the composition of the friction elements of the brake, as well as factors affecting the wear rate and concentration of particles of different sizes, based on the conclusions of other authors is presented. Based on this review, it can be concluded which quantities and factors need special attention during further research in the mechanism of formation of non-exhaust particles whose source is the vehicle braking system.