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HomeMy WebLinkAbout2012-01-03 - Stonebridge OaksITEM # - !- MEMO TO: HONORABLE MAYOR, CITY COUNCIL MEMBERS FROM: BRUNO RUMBELOW, CITY MANAGER` SCOTT WILLIAMS, DEVELOPMENT SERV ES DIRECTOR MEETING DATE: JANUARY 3, 2012 SUBJECT: WORKSHOP—CONTROLLED ACCESS TO STONEBRIDGE OAKS RECOMMENDATION: City Council to consider a traffic study conducted by the Public Works Department relative to controlled access at entrances to the subdivision and take any necessary action BACKGROUND INFORMATION: At the Council workshop on September 20, 2011 staff brought forward a request from some homeowners to install gates at all entrances to this subdivision. Council asked staff to conduct a traffic study. The traffic study is complete and attached. It shows there to be significant traffic volume based on the number of occupied structures (the subdivision is only about 25% built out), but nonetheless a very low volume overall. It is also possible that much of the excess traffic is due to construction. Staff has recommended to the homeowners that the developers wait until the subdivision is further developed and then reevaluate the situation (letter from Scott Williams to residents attached). R:\AGENDA\2012\01-03-12\wk010312.stonebridgeoaks.doc 12/27/2011 2:21:22 PM November 29, 2011 Ms. Gloria Currie 4630 Kaitlyn Lane Grapevine, TX 76051 Re: Traffic Study for Stonebridge Oaks Ms. Currie, Thank you for your patience throughout this process. Attached you will find the traffic study that was conducted for this subdivision. As you can see, the traffic counts were high based on the number of occupied structures, but still considered very low for a residential subdivision. It is also very possible that the elevated counts could be due to construction traffic. Our suggestion is that any consideration of any type of traffic control device be delayed until the subdivision approaches ultimate build out. At that time the traffic situation can be reevaluated to determine if additional control measures are warranted. Please do not hesitate to contact me if you have additional questions. Thank you, Scott Williams Development Services Director / Building Official -=-.0 "* SINE. T r x A t MEMORANDUM City of Grapevine, TX TO: Stan Laster, R.E., Public Works Director Scott Williams, Development Services Director FROM: Michael Pacelli, P.E., PTOE, Transportation Manager REV. DATE: December 1, 2011 SUBJECT: Stonebridge Oaks Traffic Volumes The Traffic Operations Division was requested to collect traffic count data at the three entrances to the Stonebridge Oaks subdivision to support the consideration of a request from residents to install gates to restrict access to the neighborhood. Figure 1 illustrates the street layout of the subdivision. Figure 1. Stonebridge Oaks Overview Map Page 2 Traffic counts were collected using Automatic Traffic Recorders, commonly called tube counters, from Tuesday, October 11 through Friday, October 14, 2001, on the three access points into the subdivision: Carly Drive (Location A), Noble Oak Drive (Location i3), and Trevor Trail (Location C). The distribution of traffic on each street connection to the surrounding roadway network is illustrated in Figure 2 for the average weekday during the study period. The top set of lines, shown in black, illustrates the total entering and exiting traffic across all three streets. 35 Carly Dr, EB (entering) — - -Carly Dr, W8 (exiting) Noble Oak Dr, E8 (entering) 30 - ^— - -Noble Oak Dr, WB(exiting) Trevor Tr, WB (entering) — - -Trevor Tr, EB (exiting) Total Entering w 25 — . -Total Exiting s i• Q` 20 v ! E15 1 1 10 F, MFAFA MIN A-hio-M, B�t-�MA, 0 0:00 1:00 290 3:00 400 5:00 6;00 7:00 800 9:00 1090 11:00 12:00 1390 1490 1500 1600 1790 18:00 19;00 20:00 21:00 22:00 23:00 Time of pay Figure 2. Weekday Average Traffic Volumes, October 11-14, 2011 Given the relatively low overall volumes, it is difficult to draw solid conclusions from the differences between entering and exiting traffic volumes at each location because the actual differences between lines in the graph often amount to just a couple vehicles per hour. It can be seen from this graph that the total entering traffic and total exiting traffic generally track fairly closely over the course of the day. If the majority of traffic using these access points were coming from the residential properties, then one would expect the majority of traffic to be exiting in the morning and entering in the afternoon. Since the entering and exiting volumes are generally balanced throughout the day, it can be assumed that the majority of traffic is not associated with the residential uses. This could be indicative of pass-through traffic with no association with the neighborhood. However, it also should be noted that information provided by development Services indicated that there were 25 occupied homes, 3 vacant homes, and 10 homes under construction around the time of the traffic counts. The approximate balance of entering and exiting traffic seen in the graph would also be closer to what might be expected in an area with construction, since deliveries, subcontractor vehicles, and individual workers may come and go from the job site throughout the course of the day, rather than peaking sharply in certain directions by time of day, as is the case with residential uses. Page 3 In order to compare the actual traffic volumes with the volumes that would be expected for the size of this residential community, forecasts of the traffic typically generated by 25 homes were made based on national data available in the Institute of Transportation Engineers' Trip Generation report (7`h edition, 2003). The results are shown in Table 1. Table 1. Traffic Volume Comparison Note that trip generation forecasts are shown for both Land Use 230, Residential Condominium/Townhouse and Land Use 210, Single -Family Detached Housing. The portion of the subdivision that is currently constructed consists of townhouses, while the units under construction are primarily single-family detached houses. Forecast Traffic Street Direction LU 230 LU 210 Townhouses Sin le-Famil im Townhouses Single -Fan Carly Dr Enter NIA N/A Noble Oak Dr Exit N/A N/A Noble Oak Dr Enter N/A NIA NIA N/A Exit Trevor Tr Enter N/A N/A Exit Table 1. Traffic Volume Comparison Note that trip generation forecasts are shown for both Land Use 230, Residential Condominium/Townhouse and Land Use 210, Single -Family Detached Housing. The portion of the subdivision that is currently constructed consists of townhouses, while the units under construction are primarily single-family detached houses. Forecast Traffic Street Direction LU 230 LU 210 LU 210 Townhouses Sin le-Famil im Carly Dr Enter N/A N/A Enter Exit N/A Noble Oak Dr Enter N/A N/A Exit Enter Trevor Tr Enter1. NIA N/A Table 1. Traffic Volume Comparison Note that trip generation forecasts are shown for both Land Use 230, Residential Condominium/Townhouse and Land Use 210, Single -Family Detached Housing. The portion of the subdivision that is currently constructed consists of townhouses, while the units under construction are primarily single-family detached houses. Forecast Traffic Street Direction LU 230 LU 210 Townhouses Single -Fan Carly Dr Enter N/A N/A Exit Noble Oak Dr Enter N/A NIA Exit Trevor Tr Enter N/A N/A Exit Table 1. Traffic Volume Comparison Note that trip generation forecasts are shown for both Land Use 230, Residential Condominium/Townhouse and Land Use 210, Single -Family Detached Housing. The portion of the subdivision that is currently constructed consists of townhouses, while the units under construction are primarily single-family detached houses. Page 4 Detached housing tends to have a higher number of occupants per unit because they more often include larger families or families with children, and as a result they generate more trips per unit than multifamily properties. Townhouses tend to have fewer occupants because residents more often consist of single people or couples, and so they have lower trip generation rates. However, since the townhouses in this project are relatively high-end and have relatively high square footages per unit, it is reasonable to assume that they may exhibit trip generation characteristics closer to what is normal for detached housing. Therefore, forecasts for both land use types were shown. As shown in the table, the actual traffic volumes are substantially higher than would be expected for an area with only 25 occupied homes. However, no reliable prediction model is available to forecast how many additional trips should be expected to be generated by the 10 additional houses that were under construction. It is also unknown how many additional trips are being generated by sales -related activity, since there are existing vacant homes and the majority of the subdivision is still remaining to be developed. It was noted that the two streets connecting to Euless -Grapevine Rd, Carly Dr and Noble Oak Dr, both tend to have slightly higher volumes of westbound, or exiting traffic. The street connecting to the State Highway 36 service road, Trevor Trail, consistently had a higher volume of westbound, or entering traffic. Therefore, there is an overall east -to -west flow through the subdivision. As with the higher -than -forecast volumes, this does not necessarily mean that there is excessive pass-through traffic, but it does align with the expected east -to -west pass-through path that one might expect given the layout of the surrounding street network. CONCLUSIONS Overall, traffic volumes were higher than would be expected for the number of occupied homes in the subdivision; even by as much as three to four times what would be expected. However, it should be recognized that the total volumes are still very low, with less than 600 vehicles per day using all three streets combined. The effect of construction and sales traffic cannot be clearly accounted for, so the remaining volumes of pass-through traffic cannot be absolutely identified. However, the traffic volumes are high enough to indicate that some amount of pass-through is likely occurring. The pass-through traffic component of the total traffic in the neighborhood cannot be quantified due to the construction and sales activities underway in the neighborhood. Since the development is less than roughly 25% completed, it is unlikely that representative pass-through traffic volumes could be identified until the neighborhood is approaching build -out with a much higher percentage of occupancy.