Air quality in connection to streets with heavy traffic is a problem that affects the environment and people's health at many places. Photo catalytic properties of materials with nano sized TiO2 have been developed in recent years. Many research projects have focused on air cleaning properties of concrete and cement based materials. It has been shown that it is possible to decrease the amount of NOx gases and VOC (volatile organic compounds) in polluted air by using TiO2 in the products. The air is cleaned only by radiation of the photo catalytic active surfaces with UV-light (sunlight). This short literature survey aims to give information about how photo catalytic self cleaning works with nano sized TiO2 and how it can be used in road constructions. The report gives a general description about TiO2 and its field of use. It will also provide a review of some commonly used analyse methods to measure the self cleaning effect. The results of a few field experiments are also reported.