“…However, in a study carried out by Gustafsson et al (2008), they found that ultrafine particles with sizes of 30-50 nm only occurred during tests with studded tires, and the major contributor of ultrafine particles is pavement wear rather than tire wear. Kwak et al (2013Kwak et al ( , 2014 also observed the generation of not only coarse and fine particles, but also ultrafine particles of the tire under various driving conditions, including constant speed, cornering, and harsh braking. They reported that the frictional heat due to the interaction between the tire and road pavement under harsh braking conditions could evaporate the organic compounds of tire, and consequently, ultrafine particles could be formed via gas to particles conversion, i.e., a nucleation process.…”