الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Implementing slip and/or flared lanes at some arms of the roundabout (RA) might be a solution to sustain the operation performance at acceptable levels.The impact of such implementation is not clear studied in most standards and researches with respect to the exact configuration of such lanes. Some limitations are clearly stated in HCM 2010 Chapter 21 such as the impact of slip/flared entry lanes’ design and configurations. The aim of this research is to develop a framework methodology for evaluating the operation performance of roundabouts which is sensitive to slip/flared lanes configurations and to provide standard guidelines for the traffic engineers. The evaluation of the operational performance is carried out using microscopic traffic simulation VISSIM.For this purpose, different VISSIM models are developed to replicate different layouts for single-lane and double-lane roundabouts considering the geometric features of slip/flared lanes’ configurations. The different layouts include inscribed circle diameter (D), slip lane merge/diverge location (X, Y), right-turn percent, flared lane length, circulating roadway width, number, number of lanes within the SL and the number of approaches that includes a slip lane. Three hypothetical balanced traffic flow scenarios and three hypothetical unbalanced flow traffic scenarios are examined and then validated through real life case study. The operation performance was evaluated by Measures of Effectiveness (MOE) that is represented by delay, LOSs, capacity, and queue length.The analysis of the results showed that various configurations of slip/flared lanes at roundabout (RA) has different impacts on the operation performance depending on the geometric elements of these lanes. Adjusting slip lane merge/diverge locations (X, Y) have significant impact on improving the average delays and queue lengths when compared to non-adjusted locations or the case of no slip lanes. However, the analysis showed that at the saturation level there is no impact of changing the X and Y values on the overall roundabout capacity. On the other hand, the inscribed circle diameter has insignificant impacts on the operational performance of the roundabouts with different configurations of the slip lanes.In the framework of the research, mathematical models have been developed to show the relation between delays, traffic volumes, roundabout diameter, and slip lane geometry elements. Goodness-of-fit of the equations are tested and found to have high R-squared values.The operation performance of single-lane roundabout with flared lane (FL) is slightly better than the same condition of roundabout without flared lane but the operation performance of double-lane roundabout with flared lane (FL) is considerably better than the same condition of roundabout without flared lane. The widening of approach entry and exit is more effective than widening only the approach entry. The double-lane roundabout capacity can be doubled by increasing the numbers of approaches that include flared lanes (at entry and exit in same time).The results are arranged and summarized to derive recommendations and to provide standard guidelines for the traffic engineers. In order to validate the guidelines, three real world roundabouts from Egypt and KSA are studied in case of adding slip/flared lanes with IIdifferent configurations. The produced guidelines showed strong correlation to the Vissim experimental results.