United States Department of Transportation
i
Investigating operation at geometrically unconventional intersections.
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2014-08-01
[PDF-8.31 MB]
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Abstract:This report documents the development of decision assistance curves (DAC) for unconventional intersections, particularly
median U-turns (MUT), continuous flow intersections (CFI), and jughandles. The operational measure of effectiveness
such as delay, fuel consumption, and emissions were computed. An economic analysis was performed to compute the net
present value (NPV) of benefits of operation and benefit to cost ratio (B/C) by estimating user’s cost, non-user’s cost,
construction cost, and operation and maintenance cost for the life cycle period. The DAC classified the region of optimal
performance of rural unconventional intersections comprising of four-lane major streets and two-lane minor streets. DAC
indicated that MUT is applicable for almost all levels of volume combinations of major and minor street approach volumes
under the presence of low left turning traffic. For medium to high left turning traffic, jughandle and CFI performed
optimally on high major street approach volumes. Furthermore, it was also observed that for a case with medium to high
left turning volumes, the use of CFI would be optimal for high major street approach volumes and high minor street
approach volumes at an unbalanced condition. The use of a jughandle would be optimal for high major street approach
volumes and its performance got better with increasing minor street approach volume at a balanced condition. However,
the jughandle performed better at high major street approach volume and low minor street approach volume at an
unbalanced condition. The study developed a spreadsheet tool called SILCC to estimate the operational measure of
effectiveness, as well as to perform a life cycle cost analysis. A sample case study performed on a 24-hour rural pattern
volume indicated high NPV of operational benefits and high B/C related to MUT compared to all other intersections for
new construction. Though the MUT-retrofit had the highest NPV, since the construction cost of MUT-retrofit is high, a
jughandle-retrofit was found to have the highest B/C.
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