Freeway Free Flow Speed: a Case Study in Italy

Results are presented relative to an experimental investigation regarding the speeds implemented on motorways in free flow conditions. The results demonstrate that the maximum speed, in free flow conditions, is to be found on flat straight stretches, with a section width of around 11 meters. In such conditions the free flow speed (FFS) is found to be at values of around 131 km/h. Such a speed tends to decrease when some of these conditions vary. In particular the dimensions which influenced the FFS are: slope, curvature, tortuousness and the width of the section. The lowest FFS value was encountered in ascent (+4,5%), on a straight stretch, section width of around 9 meters and tortuousness degree equal to 21 degrees/Km; in these conditions the FFS is found to be around the value of 105 km/h. These results consented the forming of the first consideration for the identification of the structure of the model for speed estimation, implemented by drivers, on the motorway in free flow conditions. It is believed that this information could be extremely useful in the evaluation of the level of service (LOS) in the motorway field.


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  • Accession Number: 01487002
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jul 18 2013 1:49PM