2011 Issue

11 W hile Kauai is considered the Gar den Isle and remains one of the least developed of the Hawaiian Islands, it nevertheless has some serious traffic problems. The permanent population of the island is still quaint at less than 70,000, butasingle,major,semi-circularhighwayisex- pectedtohandlemostoftheisland’svehicular traffic. Consequently, morning and evening rushhoursextend formultiplehours at a time, with traffic exhibiting all the behaviors of big city congestion including slow speeds, long travel times, and extensive queuing. Appar- ently traffic is still traffic, even in paradise. With nearly unlimited locations requiring congestion relief and insufficient funding to address them all, congestion is a problem that is perpetually in search of new solutions. More often than not, traditional solutions for mitigating traffic congestion are inadequate to address even the current traffic needs of our most problematic intersections. This is to say nothing about future needs, where the application of traditional solutions is often as insufficient as the proverbial drop in the bucket. In some cases, this limited ability to improve congestion is a factor nomatter how muchmoney you throw at the solution. Opportunity at 12300 South &Minuteman The intersection at 12300 South and Minute- manDrive inDraper, UT is a particularly good exampleofaserioustrafficprobleminneedof an innovative solution. Located only 300 feet eastoftheinterchangeatI-15and12300South, this intersection exhibited many problematic traffic characteristics including high volume left turn movements, inadequate storage capacities for turnmovements, shortdistance multi-laneweavemovements,frictionfromnu- merousbusinessaccesses,leftturnconflictsin andoutofbusinesses,signalspacingconflicts, signal coordination conflicts, proximity to the interchange, and collision rates higher than expected. Congestion at this intersection is clearlyaresultofnumerouscomplicationsthat would require a carefully tailored solution to address each of the contributing issues. Upping the ante for any potential solution is the fact that this intersection is the primary gateway into Draper City as well as the pri- mary conduit for a major economic center. Retail facilities on all four corners of the in- tersection drive much of the traffic demand into the area and represent a significant portion of the city’s tax base. Solutions that would restrict or impair business access (such as grade-separated options) could create inconveniences for drivers that might have a detrimental effect on the economic vital- ity of the area. Similarly, doing nothing out of inability to define a reasonable solution would likely result in crippling levels of future congestion thatwouldsimplydrivepotential consumers away from the area altogether. In analyzing the traffic operations at the cur- rently configured intersection, future year (2030) traffic modeling projected average delays of nearly 2 minutes, with delays for some turning movements extending for as longas7minutes.While these longdelaysare admittedly somewhat speculative (given the exponential-likebehaviorofdelayandthelike- lihood that affected drivers will find alternate routes), they did indicate the severity of the potential problem, especially when consider- ingthe fact that the intersectionwill onlyserve approximately80%oftheanticipatedtrafficin 2030. Byall accounts, it appearedthatwithout sufficient improvements, at least 20% of the anticipated traffic demand was very likely to considertakingthemselvesandtheirbusiness to some other location. An Innovative Solution Anumber of improvement optionswere con- sidered and eliminated during the evaluation process. These included traditional solutions such as grade separation and/or the addition of turn lanes and travel lanes, as well as more innovativeconceptssuchasquadrantredirec- tionandeventhecontinuousflowintersection. Theseoptionswereeliminated for a variety of reasons that included their inability toprovide sufficient benefit, their inability to adequately addressaccessconsiderations,theirexcessive right-of-way impacts, and their anticipated costs of implementation. Ultimately, the analysis process pointed quite clearly to the implementation of a Median U- turnconcept, similar to the“MichiganU-turn” concept that has been implemented in other parts of the country. The basic premise of this concept is to relocate all of the left turns away fromthemainintersectiontothreenewsignal- ized u-turn locations to be constructed ap- proximately 600 feet south, east, andnorth of themain intersection. Removing the left turns fromthemain intersectionallowsmoregreen time to be allocated to heavier movements;, improving the flow of traffic, eliminating the need for left-turn queuing and storage at the Utah’s ThrU Turn Intersection Melvin Bodily, PE Like death and taxes, traffic congestion is an ever-present reality of life that remains with us, no matter where we go.This problem was never more clearly impressed on me than on a recent trip to the island of Kauai.