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Advisor(s)
Abstract(s)
While researchers agree as to the safety benefits of turbo roundabouts, their
improvements in terms of capacity and delay remain open to discussion. This is mostly
because previous research is based on capacity models that do not fully describe the complex interactions between the traffic streams on multilane roundabouts. This paper
proposes a procedure to calculate capacity based on gap-acceptance theory. It
addresses the limitations mentioned by accounting for usually disregarded effects such as the dynamic choice of the entry lane and unequal allocation of traffic in the
circulatory lanes. Capacities were calculated for a wide range of demand scenarios
and it has been shown that only under demand scenarios that are very specific and
uncommon in real world networks, associated with very high percentages of rightturning
entry traffic, can a standard turbo roundabout be expected to provide more
capacity than the equivalent two-lane roundabout. It has also been shown that two lane roundabouts can normally be expected to provide capacities 20 to 30% above those of comparable turbo roundabouts.
Description
Keywords
Turbo-roundabout Hagring Gap-acceptance
Citation
Publisher
ICE - Institution of Civil Engineers