Abstract: Accident count is increasing day by day. Fog is one of the main causes of accidents, especially in hilly regions. As fog density increases, visibility of the road gets decreased. The drivers will not be able to see the road or any obstacle that is present. Unfortunately, few people do not slow down their vehicle even in the worst fog environment. So we are proposing a system that detects a foggy environment and reduces the acceleration of the vehicle, to avoid accidents. In the proposed system, a sensor that is directly connected to Arduino Uno is used to automatically calculate the values of temperature and relative humidity from the atmosphere. Based upon the values of dew point, the speed of the vehicle is controlled. If the Dew value is less than 2.5°C it indicates the presence of fog. Depending upon the Dew Value the complete control takes place. Also, from Arduino the data is sent to cloud through IOT module and from there we can access in App.