This paper presents the data analysis obtained using piezoelectric Weight-In-Motion measurement system. Data were collected for a six-month period. Statistical analysis showed that the vehicle loads of a particular Latvian highway have a considerable number of heavy weight vehicles and also presence of extremely heavy vehicles with a total weight more than 120t. Processed data of the vehicle gross and axle weight distribution as well as traffic intensities are remarkably different from the prototype data in current design codes. Vehicle’s time and space distribution also shows the distinction from the existing Latvian and European design experience. To develop the practically viable methodology for assessment procedures for new and existing bridges it is necessary to study bridge design loads, their character and trends. WIM systems have proven themselves to be the most effective tool for this type of study.