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Spack Memo 1-3-08 s ~ja.QJs THE TRAFFIC STUDY COMPANY Memorandum To: Joe Shamla, City of Chanhassen From: Mike Spack, P.E. Date: 1/3/2008 Re: Traffic Review of Crossroads of Chanhassen Per your request, I have reviewed the site plan and traffic study prepared by Westwood Professional Services for the Crossroads of Chanhassen proposal. The site is located on the northwest quadrant of the CSAH 18 (Lyman Blvd)/TH 101 intersection. The preliminary site plan and traffic report are both dated 12/14/07. My findings are: . The traffic report is professionally done using standard traffic engineering methodology. . Trip Generation: The data and calculations shown in Tables 2 through 6 of the traffic study are correct. The number of vehicle fueling positions at the gas station should be clarified. The traffic study assumes 10 vehicle fueling positions (defined in the ITE Trip Generation Manual, ih Edition as the maximum number of vehicles that could be simultaneously fueled). The preliminary site plan appears to have 26 vehicle fueling positions. I briefly spoke with Ryan Edstrom of Westwood and he indicated there will be 26 positions. If 26 vehicle fueling positions are proposed, the gas station would generate approximately 4,000 gross vehicle trips per day instead of 1,530 trips per day as indicated in Table 3 of the study. Westwood should provide you updated trip generation tables for your public meetings if the 10 vehicle fueling positions used in the calculations is incorrect. . Trip Distribution: The trip distribution pattern in the study was based on the traffic study prepared for the nearby Southwest Metro Transit Facility. This is a reasonable approach; however no traffic was distributed on or off of the new TH 212/TH 101 southern ramp intersection. The access to Crossroads of Chanhassen on the northeast corner of the site forms the fourth leg of this ramp intersection. The proposed development is oriented to take advantage of its location at the interchange. I would expect a notable percentage of the traffic using the site would be coming from or going to TH 212. . External Intersections: The traffic study projected the site's turning movement volumes at the CSAH 18/Site Road, TH 101/CSAH 18, and TH 101/TH 212 southern ramp intersections. This is an adequate scope for the traffic study given the area road network was recently reconstructed. The TH 101 intersections were constructed with adequate turn lanes and traffic signals. They are expected to operate acceptably with the addition of the site Crossroads of Chanhassen Traffic Review 20f3 Joe Sham/a, City of Chanhassen generated traffic (even if the gas station traffic needs to be increased 2.6 times in the traffic study). The CSAH 18/Site Road intersection is approximately 1/8 of a mile west of the TH 101/CSAH 18 intersection. CSAH 18 is designated as a class 5A Minor Arterial in Carver County's draft transportation plan. Full accesses are allowed every % mile and traffic signals are allowed at % mile spacing under this designation. A sensitivity analysis was done for the CSAH 18/Site Road intersection using Carver County's projection of 8,600 vehicles per day using CSAH 18 in 2030. It was assumed the through volumes during the p.m. peak hour would be 10% of the daily volume with 60% going westbound and 40% eastbound. The turning movement volumes developed in the traffic study were used at the intersection with an increase for the gas station traffic being 2.6 times higher. With this worst case scenario, the southbound to eastbound left turn movement will operate at Level of Service E with a maximum queue of six vehicles calculated through a simulation with SimTraffic software. This analysis suggests the CSAH 18/Site Road intersection will operate acceptably well into the future, however the developer should be notified the intersection does not meet the county's access spacing. If traffic volumes grow significantly on CSAH 18, a traffic signal will be an unlikely solution for solving backups at the intersection. The county would likely convert the intersection to a % or right-in/right-out by blocking some of the turning and/or through movements. . Cut-throuQh Traffic: The internal site road will be a public street. It is expected to attract some cut-through traffic from motorists trying to avoid the CSAH 18/TH 101 intersection. The maximum daily traffic volumes on the internal site road are expected to be approximately 4,500 vehicles per day (6,000 vehicles per day if there are 26 vehicle fueling positions at the gas station). The capacity of the road is approximately 10,000 vehicles per day with the through lanes and turn lanes proposed at its access points on CSAH 18 and TH 101. At most, I do not foresee more than 2,000 of the 8,600 vehicles per day on CSAH 18 near the site in 2030 using the internal site road as a cut-through. In a worst case scenario, the daily volumes on the road should remain below its capacity. Again, the developer should be notified that if a problem does arise at the CSAH 18/Site Road intersection the solution would be to limit the intersection to a % or right-in/right-out. They have chosen a roadway design that provides an attractive diagonal route and having the access restricted could be a long term consequence. · Roundabouts are becoming a viable traffic control measure and some believe they discourage traffic. Roundabouts are not recommended for the proposed development. They would require significantly more right-of-way and they would not discourage traffic because there would not be enough cross traffic at the driveways. . Internal Intersections: It appears the internal roadway is designed for a 30 mph speed limit (which is mandated by the State Legislature), although Westwood should provide horizontal and vertical curve dimensions to prove the roadway meets current design standards. Sight distance standards need to be met for the access driveways off of the internal site road. No objects should be placed in the horizontal sight triangles at the intersections and the Crossroads of Chanhassen Traffic Review 30f3 Joe Sham/a, City of Chanhassen roadway profile needs to provide enough vertical sight distance at each intersection. I have several traffic related concerns about the northerly driveway intersection on the internal site road, which provides access to the gas station. (1) All-way stop sign control should not be installed at the intersection as proposed. It will not meet the warrants for an all way stop sign control per the Minnesota Manual on Uniform Traffic Control Devices. The intersection would need 200 vehicles per hour, for eight hours, turning from the gas station onto the internal site road to meet the warrants. (2) The intersection appears to be at the bottom of a vertical crest, which could provide sight line problems. (3) The natural delivery route for the gasoline tankers would be from TH 212, which would force them to make almost a u- turn maneuver either coming in or going out of the driveway. The driveway is noticeably wider than the other proposed driveways, likely to accommodate these turns. The wider driveway results in there being less positive control for passenger vehicles, which could cause operational problems. (4) Vehicles turning to the east out of the gas station parking lot go into a road that is two lanes wide and then have to make a quick decision upon seeing the traffic signal at TH 101. This situation could pose a safety problem with weaving vehicles. (5) I developed several sets of turning movement forecasts for the driveway intersection and simulated them in SimTraffic. It appears the maximum queue would be five westbound vehicles. This would not spillback to the intersection at TH 101, but there is potential for spillback if I grossly underestimate the amount of cut-through traffic on the internal site road. For these reasons, I recommend the northerly access be redesigned for the gas station. There are many options to eliminate the traffic concerns, including but not limited to: (1) take the "s" out of the internal site road with two straight roads that meet at the northerly edge of the site with one curve or (2) move the access south to the straight north/south portion of the road, which would require "mirroring" the gas station layout to provide proper access. Please contact me at 952-378-5017 if you would like to discuss any of my findings. Thank you for the opportunity to review the Crossroads of Chanhassen development plan for the City.