TR9303-CS 930811 ' 'HE DEVELOPN,.NT OF ROADWAY IMPAL.., FEES IN TEXAS
Robert C. Wunderlich, P. Efi
Introduction Roadway Service Units
In Texas, the establishment of impact fees for In order to develop a system to assess new
roadways has been governed by state enabling development for the cost of roadway facilities needed
legislation since 1987. All impact fees imposed on to serve that development, a service unit that can be
new development for roadways must conform to the used to express both the supply provided by, and the
requirements of this legislation, passed as Senate Bill demand placed on, the roadway system must be
336 and now codified as V.T.C.A. Local Government identified. The service unit was defined as Vehicle
Code, Article 395~. This paper describes the technical Miles of Travel (VMT) in the PM peak hour.
process used to develop roadway impact fee systems
conforming to Article 395 in the cities of Arlington, Service Unit Supp/y
Garland, and DeSoto, Texas.
For roadway capital improvement projects, the number
These systems can be used by any jurisdiction to of service units provided is simply the product of the
assess new development for the impact created on the hourly capacity of the roadway and the length of the
roadway system in an equitable and rational manner, project. Therefore, a four lane divided roadway project
The systems also satisfy the legal requirement that a with a 650 vehile per hour per lane capacity and a
rational connection be established between new length of two miles would provide 5200 VMT.
development and an impact fee.
650 vehicles per hour per lane x 4 lanes x 2 miles
State Legislation = 5,200 VMT per hour
In Texas, state enabling legislation requires the use of Service Unit Demand
service unit and service area concepts. The service
unit establishes the relationship between land-use and The demand placed on the system can be expressed in
the demand placed on the roadway system. The use a similar manner. For example, a development
of service areas ensures that fees collected from new generating 100 vehicle trips in the PM peak hour with
development are based on the cost of roadway projects an average trip length of three miles would generate
in the vicinity of that development and will be spent 300 VMT.
only on those projects.
T/me Per/od Used To Assess Impact Fees
Process
A critical factor in determining a service unit is the time
The process of developing transportation facility impact period selected for the assessment of impact fees. The
fee systems in these Texas cities consists of three PM peak hour was selected for the time period for
basic steps, assessing impact fees based on the following criteria;
1. Determining an appropriate service unit for roadway 1. The heaviest demand for service typically occurs
demand and capacity, during this hour;
2. Determining the cost of providing each roadway 2. Roadways are sized during the planning process to
service unit. meet the needs during this PM peak hour, and
3. Determining the service unit generation of specific 3. Roadway capacity can be precisely defined on an
land uses. hourly basis.
~ Robert C. Wunderlich, P.E., Senior Associate, Barton-Aschman Associates, Inc., 5485 Belt Line Road, Suite
199, Dallas, Texas 75240
C(~st Per Service Unit '"'" C. Service area.~%re made as large as possible in
order to promo(e un!fortuity in the fees.
The second step in the overall impact fee process is
determining a cost per roadway service unit, or cost An example of a service area is shown in Figure 1.
per VMT. The .process involved three steps: (1)
Determining a capital improvements program; (2)
Developing a service area structure; and (3) Calculating 3 Mile
the cost per service unit in each service area. .Dlarneter Circle
1. Developing a Capita/Improvements Program
The first step in determining the cost per service unit is
to develop a transportation capital improvements
program. In Texas, state enabling legislation restricts
the calculation to a 10-year horizon period. Therefore,
a program of roadway capital improvements necessary
to meet 10-year traffic demands must be developed.
Construction costs, surveying and engineering fees,
land acquisition costs, and projected interest charges
and other finance charges may be included in the cost
calculations. Cost calculations were also made for
previously-built improvements which had excess
capacity available for bse by new development.
Therefore, the total capital improvements program used
to calculate fees included both previously constructed
roadways and projects which will be constructed which
provide roadway capacity that can be used by new
developments in the next ten years.
The cost of State projects are specifically excluded FIGURE 1. EXAMPLE SERVICE AREA
from inclusion by Article 395. A city may not use
impact fee proceeds to pay for its portion of State
roadway projects, even if capacity enhancements will
serve new development.
2. Determining A Service Area Structure
3. Calculating Costs Per Service Unit (VMT)
The structure of the enabling legislation requires that
fees be calculated on a service area basis and not a State enabling legislation in Texas requires that impact
city-wide average. Nonetheless, the calculations may fees for roadway areas be based on the costs within
be made on a system-wide basis within the individual each service area. The following calculations were
service area. The criteria used to develop service areas necessary within each service area:
were:
A. VMT Supply
A. The boundaries of the service areas were designed
to meet State enabling legislation requirements The amount of net roadway service unit supplied by
which essentially require that no point within a the lO-year capital improvements program was
service area can be more than three miles from the determined by calculating the total VMT of supply
boundary of the service area. provided by the roadway capital improvements program
within a service area and subtracting out the VMT of
B. Service areas were made to conform to traffic existing usage and existing capacity deficiencies within
survey zone (TSZ)boundaries which were the the service area. Deficiencies were defined by
smallest geographical area with readily available land identifying roadway segments where the hourly
use data. capacity used in calculating the amount of supply was
, exceeded by existing traffic demand.
B. 'Cost of VMT Supply ~ 1. Trip Generat~''~
The cost of supplying the service units was identified The number of vehicles generated by development in
by splitting the roadway projects into segments within the PM peak hour was based primarily on rates
each service area and adding the costs associated with published by the Institute of Transportation Engineers~
those segments, supplemented by other sources, including the North
Central Texas Council of Governments.
C. Projected VMT Demand
A key element is that adjustments were made to
The third step in this process involved determining the reduce the possibility of overcounting the impact from
VMT demand expected from new development in the new development by only counting primary trips to
lO-year period using 10-year land use assumptions in new developments and excluding both pass-by and
a travel demand model, diverted trips from the trip generation rate.
D. VMT attributable to New Development 2. Trip Length
In Texas, state enabling legislation requires that impact Trip lengths were based primarily on the information
fees be based only on the portions of the capital gathered by the North Central Texas Council of
improvements program which can be attributed to, and Governments staff in a region-wide travel survey. The
are made necessary by, new development. In each informatiOn was stratified by land use type and was
service area the number of service units required by matched to the trip generation rates where possible.
new development was compared to the number of Other sources were used to fill in the gaps including
service units supplied by the capital improvements the experience of the consultant and the City staff.
program and the proportion of the supply which could
be attributed to new development was determined. Adjustments were also made to the trip lengths to
account for travel on state highways. For example, it
E. Cost per VMT was determined that some 15% of the total VMT in
Arlington occurs on State highways. Therefore, each
The cost per service unit in each service area was trip length was reduced by 15% in Arlington. The
determined by dividing the cost of the portion of the adjustment for travel on State highways was 22% in
capital improvements program attributable to new Garland and 9% in DeSoto.
development by the number of vehicle miles of demand
expected in the lO-year period. This adjusted trip length was then divided by two to
reflect half of the total average trip length associated
Typical average engineering and construction costs per with each one-way trip. This was done to ensure that
VMT range from $650 to $950. In each jurisdiction, each new development pays only for half of each
the initial fees were set at roughly half of the vehicle-trip made during the PM peak hour to and from
calculated cost and finance costs were not included, that development.
Within each city, a wide variation of VMT cost
between service areas resulted from the requirement Finally, an adjustment was made so that no resulting
for separate calculations within each service area. trip length exceeded three miles in order to comply
Some jurisdictions have capped fees at a uniform level with the intent of the State enabling legislation, which
to reduce differences in fee rates between service implies that the development's responsibilities are
areas, limited to an 'area defined by the average trip length,
but in no event more than three miles.
Service Unit (VMT! Generation Of Specific Land Uses
3. Serv/ce unit (VMT) Generation
The assessment of an individual develol~ment's iml~act
fee is based on the premise that each vehicle-trip has The vehicle-trip generation rates and average trip length
an origin and destination and that the development on information were combined to create a service unit
one end of the vehicle-trip should pay half the costs equivalency table similar to Table 1, which lists
necessary to provide for the complete trip. Thus, a examples of the VMT rate per development unit for
new development is assessed only for a portion of each common land uses.
vehicle trip associated with that development. The
determination of the dumber of service units generated The trip generation rate per development unit is
by a new development has two components: (1) trip multiplied by the number of development units to
generation; and (2)average trip length, provide the total VMT generated by a specific
· de'velopm~nt. This total VMT is th~'"'nultiplied by the 2. They recogn~'3nd value actions on the part of
fee per VMT established within the service area developers wr~ch can decrease the costs of
containing the development to determine the total providing impact facilities. Developers receive credit
roadway impact fee. for the value of right-of-way dedication and design
and construction of major facilities.
TABLE I 3. They allow the poo!ing of developer contributions
EXAMPLE SERVICE UNIT EQUIVALENCIES within a service area for maximum effectiveness in
Trip Veh-Mi/ providing roadway infrastructure within the cities.
Dev. Trip Length Dev.
Land Use Unit Rate (miles) Unit
These systems developed in Texas can be used in any
Single Family D.U. .95(x) 3.0 2.eS(x) jurisdiction where there is a desire to assess new
Residence development fairly and rationally for the roadway needs
General Office 1,000 1.35(x) 3.0 3.99(x) they create. They are comprehensive systems which
Building SF GFA require a commitmen( to construct roadways to meet
future needs but provide mechanisms to recover the
Shopping 1,000 1.623 2.7 4.38(x)
Center SF GFA COSTS associated with that construction. They also
require jurisdictions to implement sound transportation
General Light 1,000 0.353(x) 3.0 ~.OS(x) planning and implementation programs. These are the
Industrial SF GFA dividends.that make the establishment of an impact fee
system worthwhile.
Summary
References
The transportation impact fee systems developed in
Arlington, Garland, and DeSoto provide a mechanism
so that all new developments contribute to funding
major roadway facilities in proportion to the amount of
burden they place on the system. The major features 1. Vernon's Texas Codes Annotated, Local Government
of the systems are: Code, Article 395, West Publishing Co., St. Paul,
Minnesota
1. They allow new developments to be treated
equitably regardless of their location and proximity
to major roadway systems and the timing of the 2. Trip Generation, 4th Edition, Institute of
development in relationship with the provision of the Transportation Engineers, Washington, D.C.
infrastructure.