The present Diploma Thesis aims at the investigation of cell phone use impact in vehicle traffic speed and space headways. For the achievement of this objective, appropriate data were collected through an experimental process in real road conditions of urban environment. Linear regression was used to investigate, the impact of cell phone use, driver characteristics (sex, age), traffic flow characteristics (speed and headway difference in relation to the preceding vehicle), to the vehicle speed and space headway. From the mathematical application of the models, it appears that the cell phone use leads to statistically significant decrease of traffic speed and space