Agenda - Public Works Committee - 12/13/2011

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Table 2. Ramsey Parkway & Sunwood Drive — Potential Ultimate Lane Configuration Overall Intersection Average Bela', By Approach Peak Hour Analysis Level of Ser~rice SB - Driveway EB - Sunwood Dr. NB - Sunwood Dr. 1%r - Ramsey Pkwy Condition Level of Average Level of Average Level of Average Level of Average Level of Average Service Delay Service Delay Service Delay Service Delay Service Delay AM Calibrated A 3.3 A 4.2 A 3.8 A 3.0 A 2.9 PM Calibrated A 4.1 A 6.8 A 4.1 A 4.2 A 3.9 LOS Source.- 2010 Highway Capacity tvtarrual - Unsrgnalrzed Intersections Seconds The residual capacity for the AM and PM peak hours is also listed below. AM: SB congests with a 232% increase in traffic growth above the 2030 traffic volumes. PM: SB congests with a 63% increase in traffic growth above the 2030 traffic volumes. The ARCADY operational analysis data is documented in Appendix B, pages B.1.1 thru B.1.3 Discussion of Proposed Roundabout Lane Confiauration The roundabout would operate within acceptable ranges of congestion as a single lane roundabout. But, to maintain the proposed eastbound two lanes, an eastbound partial right turn bypass lane should be used to facilitate dropping a lane at the roundabout, see Figure 2. The roundabout can also be expanded inward into the central island, with minimal rework, to create a multilane roundabout with a northbound double left and two westbound thru lanes. The ultimate lane configuration has the ability to handle any potential increases in traffic from the forecasted volumes. DISCUSSION AND CONCLUSIONS The results of the ARCADY analysis of the proposed roundabout show a LOS A for the two peak periods for the interim roundabout design, and has the ability to expand to a multilane roundabout in the future. Typically, when a roundabout is close to a traffic signal, the impacts to the signal are negligible, while the roundabout can be impacted by queue spillback from the signal. The impacts to the Ramsey Parkway and Sunwood Drive intersection will be infrequent but the roundabout is better suited to reduce the effects of the closely spaced intersections, for the following reasons: • If the Ramsey Parkway and Sunwood Drive intersection were traffic signal controlled, it would likely have the same cycle length as the Armstrong Boulevard traffic signal, assuming they both have to operate as one system due to being closely spaced. Using the same cycle length for the Ramsey Parkway intersection imposes timings that may not be ideal for the traffic patterns at the intersection. Additional operational impacts to the Ramsey Parkway intersection are likely due to the inflexibility of signal timings. • The roundabout intersection will have slower entering and circulating speeds. This will reduce the impact of queue spill back from Armstrong Boulevard. The roundabout has greater flexibility in responding to traffic demands as compared to a traffic signal constrained by timings that suit the adjacent intersection. e Ourston Roundabout Engineering Operational Analysis Ramsey Parkway & Sunwood Drive Ramsey, Minnesota Page 3