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HomeMy WebLinkAboutA002 - Memo to City Council dated August 2, 2001 regarding traffic study Memo City Manager's Office a aring People Quality Programs Exceptional Service TO: Steve Goodhue, City Council FROM: Steven L. Schainker, City Manager DATE: August 2, 2001 SUBJECT: Council Follow Up In response to your recent request, I am attaching a copy of excerpts from the traffic study prepared by Ev Cochrane's traffic engineer and the response from the City's traffic engineer. This issue is important to Mr. Cochrane,the developer of the new South Fork subdivision near Dotson Drive,because the staff is recommending that he pay for the off-site improvements such as turning lanes and traffic signals. Mr. Cochrane is emphasizing that these costs are so significant that they jeopardize his ability to move ahead with this development. He would prefer that the City assume a greater financial responsibility for these off-site improvements. I hope this information is helpful. Give me a call if you would like to discuss this issue further. \sls c: Mayor and City Council attachments trips in the proposed site plan and 184 trips in the single-family plan. The PM peak hour generates 225 trips in the proposed plan and 257 trips in the single- family plan. TABLE 4 COMPARISON OF LAND USE TRIP RATES AM Trips PM Trips Land Use Plan In Out In Out Proposed 36 139 147 78 All Single-Family 46 138 158 89 Difference +10 -1 +9 +11 Since no actual site plan was submitted, a detailed level of service analysis was not completed for the single-family plan. However, it would seem reasonable that the impact on the Lincoln Way intersections and the residential streets would be about the same as that of the proposed plan. IV. CONCLUSIONS AND RECOMMENDATIONS The following findings and conclusions were reached based on an analysis (described in detail within this report) of the traffic impacts expected from the proposed development of the Dotson property. • The additional traffic generated by the proposed development will likely reduce operations at the Lincoln Way / Franklin Avenue intersection during the evening peak hours. The overall level of service is estimated to be "D." This is primarily due to the significant delays that the westbound to southbound left turn movement will experience. The level of service projected for this movement during the evening peak hour is „E „ • The intersection of Lincoln Way / Beedle Drive will continue to operate at an acceptable level of service. • The southbound movement at the intersection of Lincoln Way / Dotson Drive will fall below acceptable levels in the evening peak hour (LOS = D). • If the recommendations offered within this report are instituted, site traffic should be able to enter and exit the site safely and efficiently with minimal impacts on traffic flow. The average vehicle exiting and entering the site is expected to experience very little delay. 14 Project-Related Recommendations • Construct left turn lanes on Lincoln Way at the Franklin Avenue intersection for eastbound and westbound traffic. Separate left turn phasing does not appear to be required based on the projected traffic flows. • Construct left turn lanes on Lincoln Way at the Dotson Drive intersection for eastbound and westbound traffic. The number of left turning vehicles exceeds 100 vehicles in the evening peak hour. This could have significant safety impacts if a left turn lane is not constructed. • Although the Dotson Drive approaches to the intersection appear to fall below acceptable levels of service, it is not recommended that a traffic signal be installed at this location at this time. This location is too close to adjacent signals (particularly Beedle Drive) to operate effectively. It is very likely that as it becomes increasingly difficult for traffic to make a left turn out of Dotson Drive onto Lincoln Way, more drivers will shift their path to Beedle Drive (making use of the existing signal). The City of Ames should monitor this intersection closely as traffic volumes increase. It may become necessary to prohibit left turns from northbound Dotson Drive to westbound Lincoln Way. • In order to alleviate some of the traffic that may use Franklin Avenue to access the proposed site, the apartment driveway layout should be designed to encourage traffic to use Dotson Drive rather than Franklin Avenue. The addition of a northbound right-turn lane at the Lincoln Way/Dotson Drive may also help in this matter. • The portions of Aplin Street and Dotson Drive that are unpaved should be paved. 15 r Memo Public Works Departn Caning Pe o Quality Progr Exceptional Se e TO: Planning and Zoning Commission Members FROM: Scott Logan, City Traffic Engineer DATE: July 13, 2001 SUBJECT: Traffic Impact Report for the South Fork Subdivision During the review of the South Fork Subdivision, staff has indicated to developers that the Traffic Impact Study Recommendations for this subdivision were acceptable except for the one concerning traffic signal controls at the Dotson Drive/Lincoln Way intersection. The study recommendations state that although the Dotson Drive approaches to the intersection appear to fall below acceptable levels of service, it is not recommended that a traffic signal be installed at this location at this time. The consultant further indicates that this location is too close to adjacent signals (particularly Beedle Drive) to operate effectively. It is also noted in the report that it would be very likely that as it becomes increasingly difficult for traffic to make a left turn out of Dotson Drive onto Lincoln Way, more drivers will shift their path to Beedle Drive (making use of the existing signal). The consultant recommends that the City of Ames monitor this intersection closely as traffic volumes increase, and it may become necessary to prohibit left turns from northbound Dotson Drive to westbound Lincoln Way. Staff does not concur with this recommendation since it is believed that the benefits of installing a traffic signal at the Dotson/Lincoln Way intersection for traffic safety purposes greatly outweighs the negatives concerning traffic flow interruptions along Lincoln Way. Staff believes that a traffic signal should be installed to provide safe "gaps" in the Lincoln Way traffic stream for motorists egressing from the Dotson Drive approach. Without these safe gaps, a significant number of right-turn and left-turning type of accidents will occur at the intersection as traffic increases. It should be noted that the projected volumes at this location will meet traffic signal warrants based on the Federal Highway Administration's "Manual on Uniform Control Devices", which is a strong indicator that traffic signals should be installed at this intersection. Staff is also concerned about the spacing of traffic signals along Lincoln Way, however, the existing traffic signal spacing along Lincoln Way has Fong been compromised resulting in lower "coordinated" speeds. Currently, most Lincoln Way traffic signals along this corridor are not spaced appropriately and a number have one block spacings including the signalized pairs between Hyland/Sheldon, Sheldon/Hayward, Ash/Knoll, Lynn/Ash, Knoll/Beach, and Welch/Hayward. Typically, this substandard spacing of traffic signals provides less than ideal traffic signal coordination timing plans whereby traffic speeds and delays are decreased along this corridor as a result. Ideally, a signalized corridor should have signal spacings at 1,300 feet and no other sidestreet accesses. In conclusion, staff believes that traffic problems would significantly increase within this area if a traffic signal installation is not placed at the Dotson/Lincoln Way intersection. First, as mentioned, an increased number of traffic accidents will most likely occur at the Dotson/Lincoln Way intersection due to the limited number of traffic gaps in the Lincoln Way stream. These accidents would primarily involve northbound (from the Dotson approach) and westbound (from the Lincoln Way approach) left-turning motorists who are egressing and ingressing into the subdivision. Secondly, traffic problems will result from the traffic diversion along local area streets used as alternate routes to signalized intersections. By not installing a traffic signal at the location, these diverted trips will be along area streets such as Tripp, Aplin, Coy, Baugnman, and Beedle that are along routes extended to the Beedle/Lincoln Way and Franklin/Lincoln signalized intersections. Most likely, these diverted trips will create additional traffic problems in the area including an increase in speeding, traffic noise, conflicts, and other traffic nuisances.