The models that correlate the road characteristics and the operating speed on tangent are studied all around the world. Although the issue of speeds on tangent sections has not been studied extensively, several U.S. and international researchers have studied operating speeds and average running speeds, design speeds, speed limits, and the impact of geometric and traffic measures on speeds. The objective of this experimental study is to get relationships of general validity for the prediction, in phase of project, of the speeds that will be indeed practiced on the infrastructure. The experimental investigation has been conducted employing traffic counters, able to record, for every vehicular passage in both senses: length, instant speed and direction of the vehicle. The plan of survey has been elaborated to satisfy different objectives of search and it has been applied to some roads belonging to the network of the Province of Salerno. The measures have been performed holding every section under observation for 2 or 3 hours. Then the data have been used for starting the formalization of some analytical relationships to predict the operating speeds. Speeding is a general problem in traffic and exploring factors underlying the choice of speed is an important task. The relationship between various measures of traffic speed, under free flow conditions, and speed limits is investigated in Southern Italy. The effect of speed limits on traffic speed is estimated. Increased speeding will likely result in augmenting the number of traffic accidents, as well as the severity of the injuries, resulting from high-speed accidents. Many drivers are aware of the negative effects of speed, exceeding the speed limit is nevertheless one of the most frequent traffic violations. This paper introduces a prediction model of operating speed and the other parameters of free flow conditions. In meaningful way, the surveyed operating speeds, always superior to posted speed limits, are correlated to the entrance one that depends on geometric parameters of the preceding curve.