The Board of Supervisors requires that all driveways and roadways
be designed to accommodate the amount and type of traffic they will
serve considering the type and character of the roadway that the driveway
or roadway will access.
A.
Purpose.
(1)
These guidelines detail the procedures to be utilized when conducting
a traffic impact study for a proposed site development which is expected
to impact traffic operations on a Township roadway. Such studies are
necessary to define the possible magnitude of the impact(s) of the
proposed development on the traffic operations of the affected Township
roadway(s) and determine improvements necessary to provide for accommodation
of the traffic due to the proposed development.
B.
Determining the need for a traffic impact study.
(1)
Traffic impact studies are conducted to enable the Board of Supervisors
to identify the potential impacts of a proposed development and determine
any roadway improvements necessary to provide an acceptable level
of service. These studies are to be conducted during the initial stages
of the site development review and approval process in order to adequately
consider the impacts the development will have on the local transportation
network.
(2)
Not all developments will have a significant enough impact to require
a traffic impact study. The use of engineering judgement is necessary
in making this determination and consideration should be given not
only to changes in projected traffic volume but also safety or capacity
deficiencies which could impact the roadway system.
(3)
In all cases, a traffic impact study will be conducted when, in the
opinion of the Board, the site development is expected to have a significant
impact on the safety and/or traffic flow of the affected roadway(s).
(4)
A traffic impact study shall be submitted along with subdivision
or land development plans when any one of the following conditions
exist or are created by the proposed subdivision or land development.
(a)
The proposed development is expected to generate 400 or more
vehicle trips per day (total inbound and outbound development traffic).
(b)
The proposed development is expected to generate traffic flow
which will be comprised of greater than 15% by aggregate, of trucks,
buses and RV vehicles. This maximum percentage of trucks, buses and
RVs will apply whether or not the development is expected to generate
400 vehicle trips per day (total inbound and outbound).
(c)
The total traffic flow on the adjoining roadway will exceed
250 vehicles per hour during the adjoining roadway's peak hour, and
25 or more of the vehicles are newly generated peak direction trips
to or from the site.
(d)
Residential, commercial and industrial subdivisions shall estimate
the expected vehicle trips based upon complete build-out of the subdivision,
including all existing and future phases of the development.
C.
Preparation of the study.
(1)
When it has been determined that a traffic impact study is required
for a proposed site development, it shall be the responsibility of
the developer to ensure the study is conducted and a final report
submitted in accordance with these guidelines. The traffic impact
study and final report shall be prepared under the supervision of
a registered professional engineer who possesses a current license
issued by the Pennsylvania State Registration Board for Professional
Engineers. The final traffic impact study report must have the seal
and signature of the supervising engineer on it when submitted.
(2)
The conduct of the traffic impact study must be in cooperation with
and coordinated with the appropriate state and local officials. Of
special importance is the need to work closely with the involved municipal
officials in determining the improvements which are to be implemented
on the affected roadway(s). Where the recommended improvements will
require a commitment from the municipality for continued maintenance
and/or operation, such as with traffic signals, the report should
indicate a commitment from the developer to accept these responsibilities.
D.
Study procedures.
(1)
General requirements.
(a)
The traffic impact study will be conducted using currently accepted
traffic engineering practices and procedures. The use of computer
programs to conduct the required analyses is acceptable; provided,
the programs reflect the most current provisions of the analysis procedures
upon which they are based. Recommended geometric or traffic operations
improvements must meet or exceed all applicable state and/or local
minimum design criteria.
(b)
The study engineer will be responsible for the collection of
all information and data required to support the study effort. When
traffic counts are required for the study, the study engineer shall
collect such data to include peak-hour turning movements on an average
day as defined in the PA Department of Transportation's Publication
201.
(c)
The procedures and requirements outlined in these guidelines
are intended to provide a basic framework for the conduct of a traffic
impact study. Additions or modifications to this framework may be
made, provided such changes are approved by the Township.
(2)
Study area characteristics.
(a)
The limits for the study area should be based upon engineering
judgement and a knowledge of the existing traffic conditions in the
vicinity of the proposed site development. The area must be of sufficient
size to include the key roadway corridors and critical intersections
which may be impacted by the proposed site traffic.
(b)
Existing and proposed land uses in the study area must be considered
in the study. Where the current/proposed land use of the site is being
modified, an analysis of the proposed changes should be made to determine
the extent to which traffic volumes for the site must be modified.
(c)
Characteristics of the study area roadway network, intersections
and the proposed site access point(s) to include geometries and traffic
control need to be identified as part of the study. Included in this
identification will be all driveways adjacent to or across from the
proposed site access point(s).
(3)
Traffic analysis.
(a)
The study area roadway network is to be analyzed for safety
and capacity sufficiency for three separate conditions: existing network
conditions, future network conditions without the proposed development,
and future network conditions with the proposed development. For each
of the three conditions, the following analyses shall be completed:
[1]
Mainline ADT volumes and turning movement volumes for all critical
intersections within the study area will be determined for the a.m.
peak hour, p.m. peak hour and the proposed development peak hour if
other than either the a.m. or p.m. peak hour of the network.
[2]
The effectiveness of the traffic signal control at all critical
intersections will be evaluated by approach in terms of vehicle stops
and delays.
[3]
Gap studies will be conducted at the proposed site access points
to evaluate the need for signal control, turn prohibitions or additional
site access points to reduce the left turn volume from the site driveway(s).
[4]
Queue length studies will be completed to evaluate the potential
for a backup of traffic from controlled intersections which could
impact other intersections, including access points to the proposed
development.
[5]
An analysis of the volume and capacity of the network and all
critical intersections will be conducted utilizing the most current
Highway Capacity Manual procedures. Levels of service will be determined
and documented.
(b)
The analysis of the existing roadway and intersection conditions
in the study area will be based upon the current geometric conditions
and traffic control operations. This analysis will serve as a basis
for determining the current adequacy of the roadway network and to
document any deficiencies.
(c)
The analysis of the future conditions without the proposed development
will document the adequacy of the study area network to accommodate
traffic in the design year(s) without the proposed development. This
analysis must include a full consideration of all committed roadway
improvements to the study area network when determining the expected
levels of service. For the analysis of the future conditions with
the proposed development, one of the key factors will be the development
of the projected site generated traffic and its distribution on the
study area network. The study preparer must fully document the methodology
which was used to complete this effort and provide sufficient information
such that the Board can verify the results. In addition, care must
be taken to ensure that adequate consideration is given to that portion
of the already projected future network traffic which will utilize
the proposed development access points. (Failure to account for this
"captured" traffic will result in a "double counting" of a portion
of the future traffic.)
(4)
Improvement recommendations.
(a)
The overall goal of this section will be to detail necessary
improvements to the study area roadway network which will provide
for a level of service for the design year(s) with the development
which is at least equivalent to the projected level of service for
the design year(s) without the proposed development. Based upon a
comparison of the traffic analysis for the future conditions with
and without the proposed development, roadway and traffic operational
improvements which will support this goal are to be identified and
analyzed. These improvements may include both on-site and off-site
roadway and traffic operational changes as determined by the preceding
analyses.
(b)
In developing the proposed improvements, the study preparer
is to consider the following:
[1]
All roadway capacity evaluations shall consider not only the
overall intersection level of service and delay but also evaluate
each approach and movement to identify any substandard values which
need to be improved.
[2]
For locations where the level of service of the design year
without the proposed development is F, the improvements shall provide
an estimated delay which will be no worse than the delay for the design
year without the proposed development.
[3]
Where new intersections are being established to serve as access
to the proposed development, these intersections must be designed
to at least operate at level of service C or better (rural conditions)
or level of service D or better (urban conditions).
[4]
For access points to the proposed development which are not
proposed to be controlled by a traffic signal, an analysis will be
completed to determine the design details for a separate left turn
lane on the adjoining highway.
[5]
For access points to the proposed development where traffic
signal control is being proposed, a traffic signal warrant analysis
shall be performed in accordance with the requirements of the PA Department
of Transportation's Publication 201. Although a left turn lane shall
be provided, an analysis shall be completed to determine the type
of signal phasing required.
(c)
The final recommended study area network with proposed improvements
will also be subjected to all the traffic analyses which are required
under the previous section of these guidelines. These analyses will
serve to document the "adequacy" of the improvements.
E.
Final report.
(1)
General.
(a)
A final report must be prepared to document the results of the
traffic impact study and the recommended improvements to accommodate
the projected traffic due to the proposed development. Since this
report will be reviewed by officials with varying levels of technical
expertise, the report must be presented in a format and context which
can be understood by both technical and nontechnical parties.
(b)
The presentation of data and analyzes results should, preferably,
be accomplished on either schematic diagrams of the study area, or
through the use of charts and/or tables. All sources of data and methodologies
which were used in the study (including computer programs) must be
properly referenced, and procedures must be properly documented to
enable a review of the appropriateness of the modification.
(2)
Contents. The final report will include the following:
(a)
Executive summary which provides a concise description of the
study area, results of the traffic analyses and any recommended improvements.
(b)
Description of the proposed development site to include a map
showing the sites location in regards to the region and the area roadway
network.
(c)
Schematic diagram/map of the designated study area showing all
major roadways and critical intersections.
(d)
Results of the traffic analyses for the three traffic conditions.
At a minimum, the following data must be shown for each of the three
conditions:
[1]
Mainline ADT and intersection turning movement counts.
[2]
Levels of service.
[3]
Projected traffic distribution and network assignment for the
proposed site.
[4]
Recommended improvements to the study area network to include
preliminary cost estimates, proposed implementation schedule and expected
levels of service for the recommended network.
The general principles of design and the minimum requirements
for the laying out of subdivisions and land developments stipulated
in this chapter may be varied by the Board of Supervisors in the case
of a project large enough to constitute self-contained neighborhood,
industrial park or commercial center. Such a project shall be developed
in accordance with a Comprehensive Plan which, in the judgement of
the Board, has made adequate provisions for all essential requirements.
Provided, however, that no modification shall be granted by the Board
which would conflict with features of any adopted long-range plan
of the Township or with the intent and purpose of the general principles
of design of this chapter. Any request for an exemption shall be in
writing and shall satisfactorily set forth the reasons therein.
