Work Package 4 of the INTRO project focuses on developing methodologies for predicting traffic conditions and for monitoring traffic safety using data measured from traffic sensors and floating car data. Data fusion methodologies on combining data from multi sources to predict travel time and traffic safety are investigated. The effect of weather on traffic conditions is also an important factor; and the development of safety indicators to monitor traffic safety using traffic sensor data are also addressed in this work package. Deliverable D4.2 is the second of three deliverables of WP4. The scope of this deliverable are: - Identification of weather parameters influencing traffic. - Identification and modelling of traffic behaviour under various weather conditions and links between traffic conditions and weather state - Software simulations and driving simulator tests of traffic behaviour under various weather conditions.