Gr av es Mi ll R o ad Co r r ido r Imp ro vem ent S tudy
Delay and LOS
Traffic Forecasting
Delay and LOS are reported from the HCM 2010 from Synchro for signalized intersections with standard NEMA phasing and all unsignalized intersections. HCM 2000 methodology results are still used to report signalized intersections with non-NEMA signal phasing. Figure 8 summarizes the average AM and PM peak hour delay and LOS for each movement for the eight (8) study intersections along the Graves Mill Road corridor. The intersection HCM outputs from Synchro can be found in the Appendix.
Project level traffic forecasting is an essential part of the corridor planning process. Transportation investments can be very large and will typically be in service for many years; therefore, future traffic projections will help to ensure these investments not only serve near-term traffic demand, but longer-term demand. Multiple sources were reviewed to determine an appropriate growth rate for a 23-year time horizon (2017 to 2040) including: • • • • • •
The results in Figure 8 indicate that under future traffic conditions, six of the nine study area intersections will operate at LOS E and F during at least one peak hour. High delays experienced for individual movements are only exacerbated under no build. Notable locations include:
Existing traffic demand Historical traffic demand Land use context using transportation analysis zones (TAZs) VDOT Statewide Planning System (SPS) Travel demand model (TDM) projections Planned development
• •
The traffic projections methodology will be applied to existing traffic counts to develop traffic volumes for use in the analysis of future conditions for the study corridor. A technical memorandum detailing the methodology is provided in the Appendix. Based on:
• • • •
1) TAZ, SPS, and TDM linear growth rates that range from 0.5% to 2.0% annually (1.25% average rate), 2) new traffic anticipated from Rosedale Farms and Elements at Old Graves Mill Road, and 3) 1.25% annual historical growth likely to continue that is unrelated to planned developments,
Gristmill Drive will operate at LOS F for both peak hours. Because traffic demand has increased since the last study was completed for the Rosedale mixed use development, key inbound/outbound movements will operate at LOS F during both peak hours under the previous configuration (not illustrated on the figures but included in the modeling). The eastbound thru movements at Old Graves Mill Road and Creekside Drive will operate at LOS E and F for both peak hours. Key 501 off-ramp movements will operate at LOS E and F for both peak hours. The stop controlled intersection at McConville Road will operate at LOS F for both peak hours. While not formally a study area intersection, multiple movements at 221.
Queuing
a 1.25% annual background growth rate, plus the site generated traffic from the planned developments will be used to forecast 2040 projections. The 1.25% linear rate has been applied to all existing – or “background” – traffic counts collected in the study area that is unrelated to traffic generated specifically by developments proposed along Graves Mill Road. Then, site generated trips from each of the two (2) developments has been applied. To note, trips from Rosedale Farms will be distributed west through the study area based on existing travel patterns. With the application of a 1.25% rate, plus the addition of the site generated trips, the effective annual growth rate along the corridor is approximately 2% in the morning peak, and 2.5% in the evening peak.
A queuing analysis was completed for the study intersections during the AM and PM peak hours. Synchro 95th percentile queue lengths in feet were reported for each lane. Table 7 summarizes the 95th percentile queue lengths during the AM and PM peak hours under no build conditions, compared against the storage length capacity for that particular turning movement. Table 7– Future (2040) No Build Queuing
INTERSECTION
Figure 7 illustrates the future TMCs for the eight (8) study intersections along the Graves Mill Road corridor.
1. Graves Mill/Gristmill
Future No Build Traffic Conditions No-build traffic conditions were analyzed to evaluate the results of future (2040) traffic demand on the existing roadway network. The intent of the no-build conditions analysis is to provide a general understanding of the baseline future traffic conditions that may then be used to evaluate the effectiveness of potential future improvement strategies.
2. Graves Mill/Millrace
The existing conditions Synchro models were used as a basis to develop the no-build models. Because this is a future scenario, planned and approved projects identified through previous efforts that are anticipated along the corridor would need consideration. Within the study area, a new signalized intersection has been included to serve the planned Rosedale mixed use development. Outside of the study area, improvements at 221 are also being planned to include dual westbound left turn lanes. These geometric modifications were included in the model. The same measures of effectiveness used to evaluate existing conditions were used to measure the quantitative performance under no-build conditions.
3. Graves Mill/Millside
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APPROACH
MOVEMENT
Graves Mill EB Graves Mill WB Gristmill NB Gristmill NB Graves Mill EB Graves Mill WB Graves Mill WB Millrace NB Millrace NB Graves Mill EB Graves Mill EB Graves Mill WB Graves Mill WB Baush Lomb NB Millside SB
EBT/EBR WBL/WBT NBL NBR EBT/EBR WBL WBT NBL NBR EBL/EBT EBR WBL/WBT WBR NBL/NBT/NBR SBL/SBT/SBR
STORAGE LENGTH
130 180
190 110 110
AM Peak 95TH QUEUE 384 #407 27 #1007 342 48 3 35 23 0 0 3 0 0 0
PM Peak 95TH QUEUE 397 #850 82 #902 575 16 430 88 134 0 0 3 0 23 98
