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Vanasse Hangen Brustlin, Inc.
B 2.3.2 Seasonal Variation
The New Hampshire Department of Transportation (NHDOT) “Policy Relating to
Driveways and Access to the State Highway System” requires that traffic studies
consider traffic operations based on “peak month” conditions. This methodology
provides a conservative approach to traffic forecasting for situations where studies
can ultimately result in the design of roadway or intersection improvements. For this
reason, the traffic volume data used for this evaluation were adjusted to reflect a
peak month. Historical traffic data from nearby NHDOT permanent count stations
were reviewed to determine seasonal traffic variations throughout the City of
Nashua. The data indicates that June typically represents the peak month condition.
Therefore, the weekday peak hour traffic volumes collected in January were
increased by 15 percent to reflect June conditions. Historical traffic data was
adjusted to reflect June conditions as necessary.
Base condition traffic volume networks were developed for the 2017 weekday
morning and weekday evening peak hours using the traffic volumes counts
conducted for the study, historical traffic data, and the completion of the Broad Street
Parkway. Worst case morning and evening peak hour networks were developed
using the individual location peak hours to provide a conservative analysis. Figures
8 and 9 depict the 2017 traffic volume networks for the weekday morning and
evening peak hours, respectively. The 2017 volumes are considered the existing or
No Build conditions for the purpose of this report.
B 2.3.3 No Action Traffic Operations
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15
Measuring the volume of traffic throughout the study area roadways and
intersections quantifies the vehicular traffic demand, but does not give an indication
of the quality of traffic flow. To assess the quality of traffic flow, capacity analyses
were conducted to determine how well the intersections serve the traffic demands
placed upon them during peak hours. The evaluation criteria used in the operational
analyses is based on the methodology presented in the 2000 Highway Capacity
Manual’.
The primary result of an intersection capacity analysis is the assignment of level of
service (LOS), which is a qualitative measure describing operational conditions. The
capacity analysis utilizes factors such as speed and travel time, density or freedom to
maneuver, traffic interruptions, comfort, and convenience to provide an index to
quality of traffic flaw. Six levels of service are defined ranging in letter designation
from LOS A to LOS F, with LOS A representing the best operating conditions and
LOS F representing the worst.
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2000 Highway Capacity Manual, Transportation Research Board, Washington, 0.C.
Existing Conditions
