TRAFFIC IMPACT STUDY - EXECUTIVE SUMMARY - HNTB

A new mixed-use residential/commercial development to be titled Bishops Gate PUD (Planned Unit Development) is being proposed for construction on property on WestHigh Street near Cary Parkway and Davis Drive in Cary, NC. The proposed facilities include 270 residential units, 30,000 square feet (SF) of office development, and a 42,000 square foot church. Figure 1 shows the general site location of the Bishops Gate PUD. The proposed site is located in undeveloped tracts of land between Davis Drive and Cary Parkway in the southwestern part of Cary. For the purposes of this analysis, all facilities are assumed to be complete and fully operational by the year 2008. This report analyzes the full build-out scenario for the year 2008, the no-build scenario for 2008, as well as 2002 existing year traffic conditions.

The proposed site will have two direct access links to Cary’s local and regional thoroughfares. One connection currently exists as WestHigh Road, which connects to Cary Parkway. The other connection will be an extension of WestHigh Street through the Bishops Gate PUD, connecting to Davis Drive directly across from the existing Farm Pond Road intersection with Davis Drive. It is assumed that parking will be provided internally for individual residences and commercial parcels and that some internal circulation roadways will be developed to convey PUD traffic onto WestHigh Street.

This report analyzes and presents the traffic impacts that the Bishops Gate PUD site will have on the following intersections along Cary Parkway (south to north):

• Cary Parkway and Old Apex Road
• Cary Parkway and WestHigh Street
• Cary Parkway and West Chatham Street

In addition, the report analyzes the traffic impacts to three intersections along Davis Drive (listed south to north):

• Davis Drive (Salem Church Road) and Old Jenks Road
• Davis Drive and Farm Pond Road / Proposed WestHigh Street extension
• Davis Drive and Park Village Road / MacArthur Park Driveway

This study does not include any analysis of potential future internal roadways or minor local access streets currently intersecting WestHigh Street.

2. EXISTING CONDITIONS

All of the six intersections analyzed are existing. Figure 3 displays the existing study area laneage. The intersections of Cary Parkway / Old Apex Road and Davis Drive / Old Jenks Road are currently signalized. All remaining intersections are unsignalized. Davis Drive and Cary Parkway are regional arterial facilities and Old Apex Road serves as a minor arterial for the Town of Cary. WestHigh Street, West Chatham Street, Old Jenks Road, Farm Pond Road, and Park Village Road provide local connectivity to residential subdivisions and retail/commercial developments.

 

3. PROBABLE IMPACTS OF THE DEVELOPMENT PROJECT

The projected trips generated by the proposed Bishops Gate PUD site were based on the ITE Trip Generation Manual (Institute of Transportation Engineers, 6^th Edition, 1997). Each facility was separately reviewed to determine the best site trip generator independent variable. The proposed 30,000 square feet of commercial space was analyzed as the "General Office Building" ITE Land Use Category. Based on traits such as number of previous studies and which criteria better fit the specific sites, it was determined that the planned church and commercial space would best be analyzed based on gross leaseable floor areas and the residential units as single family detached housing. This analysis does not reduce the number of estimated site trips by a passby reduction factor per documentation found in the ITE Trip Generation Manual, 5^th Edition and the February 1995 Update of the 5^th Edition. No reduction was made due to the fact that these land uses are not typically associated with passby trips. A truck percentage of two percent was assumed for site generated traffic. Trip generation results used the average rate methodology to calculate the number of trips. This provides a more accurate estimate than using the derived equation-based methodologies. The equation-based methods often overpredict site trips that are not realistically generated by relatively small individual parcels, like the commercial space proposed for the Bishops Gate PUD.

 

With the addition of new peak hour trips during the AM peak period and the PM peak period, there are potential impacts to the study area intersections caused by the influx of site traffic. This is especially true for the analyzed intersections of Cary Parkway / WestHigh Street and Davis Drive / Farm Pond Road (WestHigh Street extension). These intersections will experience a high percentage of site traffic impact at multiple approaches, adding to heavy north/south vehicular movements along both Cary Parkway and Davis Drive during peak travel periods. Traffic to and from the proposed site access points onto these existing facilities has the potential to cause queuing problems or excessive delays for vehicles attempting to exit the PUD during the peak hours. In addition, the Cary Parkway intersection with West Chatham Street currently experiences constrained conditions with traffic movements operating near capacity and causing potential safety problems during the peak periods. The Town of Cary is planning to widen Old Apex Road by the 2008 site buildout year, which will relieve some capacity problems at its intersection with Cary Parkway.

 

4. TRAFFIC OPERATIONS ANALYSIS

Of the six intersections analyzed, none currently operate at undesirable levels of service. Analysis at Cary Parkway and West Chatham Street initially indicates that existing traffic operations produce lengthy delay, but a field operational delay study noted that actual delays are much lower than what is calculated by operations analysis software (HCS). Cary Parkway exhibits heavy peak period traffic volumes that can at times limit the opportunity for vehicles turning from W. Chatham Street. This intersection’s operations will become more congested in the future 2008 scenarios, but not to a degree that would cause complete failure for critical movements. Figures 4-8 display the existing and projected traffic volumes used in this analysis.

Future year analyses indicate that the intersections of Davis Drive / Park Village Road and Cary Parkway / WestHigh Street, will operate unacceptably with or without site traffic. Conditions are expected to worsen for the minor street stop-controlled approaches at these intersections. No significant delay is expected for the major approaches at these intersections. The addition of site traffic will cause a similar problem to occur at the intersections of Cary Parkway / WestHigh Street and Davis Drive / Farm Pond Road (WestHigh Street extension) for the minor approaches. In addition, 2008 analyses with the addition of site traffic indicate that the intersection of Cary Parkway and Old Apex Road will operate with excessive overall delay. This intersection, even with improvements to Old Apex Road, is near or at capacity with or without site traffic in 2008. No other study area intersections face deficient operations as the result of additional Bishops Gate PUD site traffic.

A summary of the traffic operations for each intersection, related to vehicular delays (intersection average as a whole if signalized, critical movement if stop-controlled) and Level-of-Service (LOS) is shown in Table ES-1. The table also indicates LOS and delay values calculated through the use of traffic operations simulation software. Simulation is an effective tool for more accurately predicting operations under future scenarios.

V. MITIGATION RELATED TO THE PROJECT

Figure 9 shows the operationally deficient movements and their corresponding delay. Figure 10 presents the recommended improvements described below.

There are no recommended improvements to be made by the Town to correct current deficiencies, or deficiencies expected without site traffic in the 2008 No-Build scenario.

The recommended improvements to be made to mitigate site traffic impacts specifically are to widen the existing WestHigh Street approach at Cary Parkway to include separate right and left-turning lanes with appropriate pavement delineation and at least 150 feet of turning bay storage. Also, to mitigate impacts at the Cary Parkway / Old Apex Road intersection, the left-turn phasing for eastbound Old Apex Road should be changed to allow permitted turns in addition to the protected phase. This simple upgrade will allow enough marginal improvement to cause the signal to operate with slightly less delay than the 2008 no-build condition.

For the other intersections that experience movements with excessive delay, there are no recommended improvements. In every scenario, with or without site traffic, the movements (usually the left-turns out of the subdivision minor streets) will fail in either case. Restriping the lanes to separate movements at these intersections does not improve operations to any significant degree. Signalization, although an option to produce acceptable operations, is not recommended because the minor street volumes do not warrant the installation of a signal, and the proliferation of signals along both the Davis Drive and Cary Parkway corridors would cause unnecessary detrimental delay to the through traffic.

Operations analysis and simulation techniques show that vehicular queues at these minor street approaches are not excessive in peak periods. In addition, many of these intersections are located upstream or downstream of nearby existing traffic signals that provide gaps in the major street traffic that will allow minor street turning movements adequate opportunity to complete their maneuvers. Operations for the affected turning movements will likely improve to a significant degree in the off peak periods, though these periods were not specifically analyzed for this study.

The intersection of Waldo Rood Road and Davis Drive is 5800 feet from Bishops Gate PUD and exceeds the one-mile limit for Traffic Impact Studies.

The intersection of Waldo Rood Road and Davis Drive was studied as part of the Sears Farm PUD December 2001. That study indicates the intersection will operate at level of service D/C in 2006 with full Sears Farm development and the town’s widening of Davis Drive.

The proposed Bishops Gate PUD will only add an additional 1% traffic to the intersection at build out. The intersection should operate at level of service "D" or better with the development of Bishops Gate PUD.

Traffic volume on Waldo Rood Road should decrease with the construction of Westhigh Street (Cary Parkway to Davis Drive).

Giverny Place: The engineer needs to determine the connectivity index for this development. This will determine the traffic service to Giverny Place. The existing grade crossing of the railroad at existing Westhigh Street R/W will be eliminated and relocated to the new alignment of Westhigh Street. Does Giverny Place need to be extended to AR-1?

Modena Drive: The existing residents of Modena Drive will find the connection to Westhigh Street more convenient than the residents of Bishops Gate traveling to MacArthur Drive. As a result, the traffic volume on Modena Drive at MacArthur Drive should decrease with the construction of Westhigh Street from Cary Parkway to Davis Drive.

Traffic cut thru on Westhigh Street. Today, the only connection between High House and Old Apex Road for Cary Parkway and Davis Drive traffic is Waldo Rood Road.

With the construction of Westhigh Street between Cary Parkway and Davis Drive, the traffic volume on Waldo Rood Road should be reduced. That traffic volume will move to the Westhigh Street corridor. This cut thru traffic was not included in the traffic study and is not created by the development of Bishops Gate PUD.

Chatham Street @ Cary Parkway The traffic signal warrants for a traffic signal are not met. However, if the average intersection vehicle delay exceeds 35 seconds (level of service D) then a traffic signal would be required with or without the Bishops Gate PUD.

Westhigh Street @ Cary Parkway The construction of Westhigh Street from Cary Parkway to Davis Drive and the new collector street traffic will meet the requirements for a traffic signal at the intersection. The traffic signal should operate at level of service "D" or better.

Westhigh Street @ Davis Drive The construction of Westhigh Street from Cary Parkway to Davis Drive and the new collector street traffic will meet the requirements for a traffic signal at the intersection. The traffic signal should operate at level of service "D" or better.

Park Village @ Davis Drive The widening of Davis Drive from Cary southern town limits to Morrisville will meet the requirements for a traffic signal at the intersection. The traffic signal should operate at level of service "A" or better.

Existing railroad and future commuter service The NCDOT rail division indicates that the existing railroad bed is the lowest standard for railroads with speeds of less than 10 mph. Today, a freight train travels to Durham in the morning and returns to Apex in the afternoon.

This rail line is proposed in the NW Area Plan to provide commuter service in the future. This is the only existing rail line to provide service between Apex to Durham.

Davis Drive only two lanes in Apex. The existing two lane Davis Drive in Apex is adequate for the existing volume and the traffic from Bishop’s Gate. As traffic continues to increase in Apex, Davis Drive will need to be built to the same standard as the Cary section. At this time, Apex nor NCDOT has plans to improve this road.

Driveways on Westhigh Street: The Comprehensive Transportation Plan has Westhigh Street listed as a collector. This collector will have traffic volumes that are unsafe for driveways.

Olde Salem Addition (60 units) not included in traffic study. The Olde Salem Phase 2A & 2B was approved in April 2002. The proposed 59 dwelling units did not require a traffic impact study. This addition was not included in the background traffic as a separate development. This study did include a 3.5% annual growth rate to account for other development in the area.

This traffic increase will increase the growth in background traffic to:

Since this traffic is not generated by Bishops Gate PUD, it will not change the mitigation required for the PUD.

Timing of Traffic counts in the Bishops Gate PUD TIA. The timing of traffic counts is determined when the request for a TIA is received (5/17/02). Traffic volume variation is created by many factors such as day of week, time of year, schools, shopping, and employment.

• Be advised that the Projected Number of Additional Students is only a rough approximation. The actual number of students will vary depending on several variables, such as dwelling unit type, number of bedrooms, dwelling size, and other factors. A more definitive estimation will be done at the time of site plan submittal, which is when the applicant is required to secure a Certificate of Adequate Educational Facilities from the Wake County School System.