HomeMy WebLinkAbout15- WTI Study Bozeman Travel Demand Forecasting Model and Traffic Impact
Study Integration
Phase I: Initial Investigation and Scoping
by
Pat McGowen,
Research Engineer
of the
Western Transportation Institute
College of Engineering
Montana State University—Bozeman
A scope of work prepared for the
City of Bozeman
September 2014
Bozeman TDFM Table of Contents
TABLE OF CONTENTS
Listof Figures................................................................................................................................. ii
BackgroundSummary.....................................................................................................................I
WorkPlan........................................................................................................................................5
Task1: Literature Review and Informal Interviews....................................................................5
Task 2: White Paper and Presentation Development ..................................................................5
Task3: Stakeholder Meetings .....................................................................................................5
Task4: Scope of Phase Two........................................................................................................5
Schedule...........................................................................................................................................6
Budget..............................................................................................................................................7
Staffing ..........................................................................................................................................25
PatMcGowen............................................................................................................................25
TaylorLonsdale.........................................................................................................................25
NaCui........................................................................................................................................26
SupportStaff..............................................................................................................................26
Western Transportation Institute Page i
Bozeman TDFM List of Figures
LIST OF FIGURES
Figure 1: TIS Trip Distribution Using TDFM (source: De1DOT, 2014).........................................3
Figure 2: Example of WTI Research of TDFM Model for Rural and Small Urban Use................4
Figure3: Project Schedule...............................................................................................................6
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Bozeman TDFM Background Summary
BACKGROUND SUMMARY
The City of Bozeman is once again seeing a very high level of development pressure, similar to
the extreme growth of the mid-2000s. With the increase in traffic growth, fueled particularly by
higher density development that is growing in frequency, the City of Bozeman would like to
revisit and possibly revise the current approach for traffic modeling and the model's implications
to transportation system investment decisions.
The current development standards require any new development to complete a traffic impact
study (TIS) as part of the development application. A TIS contains a traffic impact analysis
(TIA) that predicts how the traffic added by the development will impact the transportation
system (note that some people use TIA and TIS terms interchangeably). In the past, the city
development standards required the TIA to include all intersections within one mile of the
development. The requirement is now that the analysis only looks at impacts within one half
mile of the development. The City of Bozeman has concerns that this narrow view of traffic
impact is too simplistic and is not serving to adequately inform decisions on city wide
transportation system investments. The TIA can often be a point of debate in the public process
for new developments. The current methodology of having the developer's engineer complete
the TIA may lead to inconsistency in methodology as each developer may hire a different
engineer. Each engineer may utilize different assumptions in distributing traffic from the
proposed development. How the traffic generated from a development is distributed is a key
factor in determining the level of impact to adjacent neighborhoods and intersections.
Every five to seven years the city of Bozeman updates the Bozeman Area Transportation Plan.
Part of this update includes an update of the travel demand forecasting model (TDFM) for the
city. This modeling is completed by the Montana Department of Transportation (MDT) and
includes updating the street network and land uses to predict future traffic volumes. The city of
Bozeman would like for this model to be updated more frequently and a system wide approach
be developed to evaluate the transportation investments that individual developments helps to
make.
These two processes (TDFM and TIA) use similar methods to predict future traffic impacts.
Table 1 provides a very generalized comparison of travel demand forecasting models (TDFM)
and traffic impact analysis (TIA).
Western Transportation Institute Page 1
Bozeman TDFM Background Summary
Table 1: Comparison of TDFM and TIA
Model Step TDFM TIA
Trip Generation `g 4 6 3 Attributes
estimates the number - �I of a single
of trip ends. _ I developm
Zone ent
attributes (e.g., number of homes, (number
number of employees, median - of homes,
income) results in trip ends per square footage) result in trip ends
zone per development
Trip Distribution Each zone to zone
matches each home pair are considered
trip end with a non- collectively
home trip end so that considering travel
the activity locations times to match
of a round-trip are every trip end
determined. Trip ends are assigned to
driveways and directions based on
existing street traffic.
Mode Choice
determines the most OV7�
likely mode (walk, ": Typical Typical
bike, transit, auto) the percent splits are assigned to trips percent splits are assigned to trips
traveler will use.
Route Choice assigns > User equilibrium The paths
each trip to the 1?�.�.�— models place the identified in trip
transportation ~r = trip on the most generation are
network '-' ' likely path totaled up and
considering the n w added to existing
congestion created traffic to
by all other traffic resulting in determine intersection turning
traffic flows for every link movements.
(intersection turning movements
can also be derived).
Spatial and temporal The region The individual
scope determines the (city, multi- development and
size of the study area, city, county direct neighboring
how frequently the S11000 or multi- streets (e.g., major
model is created and • 0� county) is intersections within
the future target year analyzed '/z mile) are analyzed for baseline,
collectively with a base year model partial build-out, full build-out.
and a 20 year projection. The These are completed for every new
model is updated every few years. development.
Western Transportation Institute Page 2
Bozeman TDFM Background Summary
The obvious similarity leads one to wonder why the two models are not combined. Some of the
challenges to combining TDFM and TIA are:
• TDFM takes considerable calibration and validation effort such that the frequency of
updating TDFM is years apart and not suitable for TIAs that are done, in some cases,
almost monthly. The cost of the license for software used to develop TDFMs can be as
much as $10,000.
• The geographic and temporal scale of the two are different and not easily merged.
• With any modelling effort, there is a balance between accuracy and level of effort. A
more accurate model requires more local data collection, more analytical work and more
model testing. Although the underlying intents of TDFM and TIA are to predict traffic,
the specific purpose is different such that each focuses on different accuracy needs.
Some major metropolitan areas do combine these processes. TISs are still done individually, but
the trip generation data (i.e., the trips created by the development) are input into the TDFM to
determine the destination, mode and route of each trip based on the regional TDFM. Delaware,
for example, has been doing this informally over the past decade, but made it a requirement for
all TIS/TIA in 2013. An example of trip distribution using the TDFM is shown in Figure 1.
Delaware Department of Transportation, who maintains the TDFM, provides these trip
distributions along with a list of intersections that must be included in the TIS. The threshold for
intersections considered is any that project more than 50 site generated vehicles entering during
the peak hour.
TI5 Model Process:
TIS Site Trip Distrlbutlon Model Estimated Origin-Destination
Silver Woods SR76 Patterns.
Single Family Units Only "Leh/Right"at Proposed Site
June 19,2014 e%E nt re nce Used for Access Design.
239.
-_ hrvd �k t0)r
�h9r n mnA - j
SITE p
i
hQ� I
Figure 1: TIS Trip Distribution Using TDFM (source: DeIDOT, 2014)
Because of the size and resources of these MPOs, one or more staff can be devoted to upkeep of
a single TDFM while also providing this trip distribution service to engineering firms conducting
TISs. The City of Bozeman is probably not large enough to warrant this level of dedicated
resources. If a process can be developed that is streamlined to balance the level of effort required
with the model sensitivity, it could result in an annually updated TDFM that could be used to
distribute trips and identify impacted intersections for each TIS/TIA. There are several potential
benefits:
Western Transportation Institute Page 3
Bozeman TDFM Background Summary
• Intersections to include in TIS/TIA could be determined based on impact not distance.
• A more frequently updated local TDFM can improve local planning (infrastructure
improvement scenario evaluation and problem future identification)
• TIAs should use existing traffic counts and traffic from nearby planned developments as
a baseline in the analysis. One benefit to this centralized approach to distributing trips
generated by proposed developments is a central repository making it easier to find the
projected traffic for planned developments.
• The trip distribution method is more consistent across all TIAs.
• Although this process, or portions of this process could be managed by the City of
Bozeman, Gallatin County, MDT, and/or a consultant; if WTI were involved it could
dovetail with current research. Research at WTI has focused on this issue of improving
the rapid assessment TDFM for use in high growth rural and small urban communities,
understanding the balance between level of effort (resources available) and improving
accuracy. One recent study resulted in a process that could be added to the rapid
assessment model to more accurately account for urban form (Figure 2). In other words,
locations within the study area that had higher densities and better land use mix resulted
in different travel patterns. For this study WTI used the TDFM model developed for the
2007 Bozeman Area Transportation Plan and updated it to 2010 to be used in this
research as a case study. Bozeman is a great study site for this research topic because it
is a small urban city with high growth. WTI involvement in this process will provide
additional benefits of:
o Leveraging research funds for TDFM updates,
o Providing research opportunities for students, and
o Allowing the potential to add functionality to the TDFM through joint
research/implementation efforts (e.g., add bike/transit networks, create consumer
choice mode model, intersection delay).
Much New Data Needs None
High Sensitiveto Urban Form
Ilk
High Level of Effort Low
7 Model Berger Modell Model
Figure 2: Example of WTI Research of TDFM Model for Rural and Small Urban Use
Western Transportation Institute Page 4
Bozeman TDFM Research Plan
WORK PLAN
This scope of work details tasks needed to develop a process for an annually updated TDFM for
the Bozeman area, and integration of the TDFM with TIS/TIA traffic distribution.
Task 1: Literature Review and Informal Interviews
To take advantage of existing methods already developed, cities that integrate their TDFM with
TIAs will be investigated through collecting documentation and phone interviews. Information
will be collected on how data is updated, modelling methods, business systems, funding
mechanisms, etc.
Task 2: White Paper and Presentation Development
Based on Task 1, a straw-man process will be developed. This process along with a background
and summary of issues will be compiled into a white paper and presentation materials.
Task 3: Stakeholder Meetings
The white paper and presentation materials developed in Task 2 will be presented to various
groups. They could include city commissioners, MDT urban planning group, and local
consultants. The purpose of these meetings is two-fold. First, it will provide an open discussion
of issues that need to be addressed within the TDFM/TIS process. These issues could be specific
to modelling methods, legal/political problems, coordination issues, etc. Second, it will help to
educate the parties involved in the TDFM and TIS processes as to the proposed process and
garner support.
Task 4: Scope of Phase Two
This effort is envisioned to have two phases. This scope covers Phase 1. If no fatal flaws are
discovered during this investigation, Phase II provides for the first year implementation and
development of guidance documents (manuals, guides, MOUs, and reports) needed for the
continued maintenance of this process. Currently the scope of Phase II is expected to include:
• Implementation and testing of necessary conversions of current TDFM model,
• Review and testing of a selection of previous TIS reports to test and compare the TDFM
trip distribution, mode choice and routing methods,
• Development of management systems (processes, deadlines, file formats, reporting, etc.),
• A national peer review of model process,
• Documentation, and
• Education and outreach.
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