©Tatiana Tereshchenko, Candidate of Chemical Sciences, Senior Research Officer, e-mail: email@example.com, ORCID: 0000-0001-7584-9031
N.P. Shulgin State Road Research Institute State Enterprise
PRIORITY POINTS OF ROUNDABOUTS DESIGNING
Abstract. Roundabout is such form of road traffic management on at-grade intersections that directs traffic flows counterclockwise around a central island giving priority to the circulating flow. Roundabouts were implemented in road design and construction in the early 1970-s and proved itself as the road safety increasing type of at-grade intersections through transport flow speed self-mitigation.
One of the valid aspects of roundabouts designing is roundabout capacity estimation. In the presented paper, the various approaches to roundabout capacity estimation were reviewed and then analyzed for the possibility of their application for the road design according to the ukrainian building codes.
The worldwide practiced models of roundabouts capacity estimation are based on the stochastic gap acceptance theory and on the regression analysis of the empirical data. The stochastic models simulate the distribution of gaps between homological position of circulating transport units and taking these gaps by entry transport units. Most stochastic models primarily apply the exponential regression equations and don’t account the impact of roundabout geometry on the behavior of drivers. The basic model of roundabout capacity estimation relating the roundabout geometry is so-called TRL model evaluated by transport Research Laboratory, UK; this model is described by a linear regression equation. According to the analyzed results of investigations, all of the practiced models of roundabout capacity estimation operate with “entry capacity” concept for one separated entry.
It is to note that Ukrainian building codes establish the design strength of road pavement as a function of average annual daily traffic intensity that should be calculated from data on traffic intensity (towards the end of the standard service life of a pavement) and vehicles flow composition counted in forward and backward directions. Thus, according to the Ukrainian building codes, the “entry capacity” concept is unacceptable for estimation of roundabouts capacity as a part of designing of a road pavement and it is advisable to consider the development of a methodology for estimation the total capacity of roundabouts an actual task.
Keywords: motor roads design, roundabout, gap acceptance theory, entry capacity, total capacity.
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