This paper presents model for predicting operating speeds on tangent sections of two-lane rural roads. The speed data of 20 drivers were continuously recorded along an 18 km long section of a state road D1. The data were used for determination of maximum operating speeds on tangents and their comparison with speeds in the middle of tangents i.e. speed data used in most of operating speed studies. Analysis of continuous speed data indicated that the spot speed data are not reliable indicators of relevant speeds. After that, operating speed models for tangent sections were developed. There was no significant difference between model developed using speed data in the middle of tangent sections and model developed using maximum operating speeds on tangent sections. All developed models have higher coefficient of determination then models developed on spot speed data. So, it was concluded that the method of measuring has more significant impact on the quality of operating speed model than the location of measurement.

operating speed; rural roads; spot speed data; model for prediction