For Users of Highway Statistics
Purpose of Information
The Federal Highway Administration (FHWA) collects
from the States and publishes in Highway Statistics information
necessary to support its responsibilities to the Congress and
the public. This information is used in the development of highway
legislation at both the Federal and State levels. The information
is also used in preparing legislatively required reports to Congress,
in calculating and evaluating Federal fund apportionments, in
keeping State governments informed, and, in general, as an aid
to highway planning, programming, budgeting, forecasting, and
fiscal management. It is also used extensively in the evaluation
of Federal, State, and local highway programs. From an FHWA
perspective, the information in Highway Statistics meets
the Federal need of providing a national perspective on highway
program activities very well. Since this information was developed
primarily to meet FHWA and State needs in administering the Nation's
highway programs, other users need to exercise thoughtful care
in using this information for other purposes.
Information published in Highway Statistics
comes from a number of sources. These sources include various
administrative agencies within the 50 States, over 30,000 units
of local government, the FHWA, other Federal agencies, and the
five U.S. territories.
Information included in Highway Statistics
is the result of a cooperative effort between the FHWA and the
States. Nearly all of the data provided to FHWA, including the
Highway Performance Monitoring System (HPMS) data, come through
State Departments of Transportation from existing data bases or
business records of many individual State and local governmental
agencies, including metropolitan planning agencies (MPOs). The
existing data bases and record keeping systems of these governmental
units were designed and are maintained to meet their individual
Data quality and consistency of information
published in Highway Statistics are, therefore, dependent
upon the programs, actions and maintenance of sound data bases
by numerous data collectors, manipulators and suppliers at the
State, local and metropolitan area levels. In general, specific
data items that are used by the collecting agency are likely to
be of better quality than data items which are collected solely
for the FHWA. Data quality and consistency are also dependent
upon the nature of the individual data items and how difficult
they are to define, collect, etc.
HPMS data are collected in accordance with
the Highway Performance Monitoring System Field Manual for
the Continuing Analytical and Statistical Database. This
document contains standard codes for the various data items to
be reported in a consistent format.
Highway statistical data other than the HPMS
are collected in accordance with A Guide to Reporting Highway
Statistics (the Guide). Reporting procedures contained in
the Guide are not rigid standards; rather, they represent a reporting
reference system that the FHWA recommends the States use in collecting
and reporting State and local highway data to the FHWA.
Nearly all of the State reported data are analyzed
by FHWA for consistency and for adherence to reporting guidelines.
In a number of cases, data are adjusted to improve consistency
and uniformity among the States. The analysis and adjustment
process is accomplished in close working relationship with the
States supplying the data.
Using Data for Comparisons
Even when data are consistently collected and
reported, users need to recognize that highway statistical information
is not necessarily comparable across all States. For many of
the data items reported in Highway Statistics, a user should
not expect to find consistency among all States, due to many State
to State differences. When making State level comparisons, it
is inappropriate to use these statistics without recognizing those
differences that impact comparability.
Use of reported State maintenance expenditures
provides a clear example. Maintenance expenditures per mile can
vary between States depending upon a number of factors including
differences such as climate and geography, how each State defines
maintenance versus capital expenditures, traffic intensity and
percent trucks, degree of urbanization, types of pavement being
maintained, and the level of system responsibility retained by
the State versus that given to other levels of government. It
would be inappropriate, therefore, when using data from Highway
Statistics to compare per mile maintenance costs across all
States to draw any conclusions without taking into account the
differences that should be expected in these parameters
based upon differing State conditions.
If choosing to compare State data, the user
must be prepared to thoughtfully select a set of peer States that
have similar characteristics in relationship to the specific comparison
being made. Improperly selected peer States are likely to yield
invalid data comparisons.
Differences that the user needs to consider
in determining suitability of peer States for data comparison
purposes include characteristics such as urban/rural similarities,
population density, degree of urbanization, climate, geography,
differing State laws and practices that influence data definitions,
administrative control of the public road system, similarity of
the basic State economies, traffic volume similarities, and the
degree of State functional centralization.
To facilitate the selection of peer States
for possible comparative purposes, a table listing a number of
data items which might be considered follows this discussion.
Most of these data items are available in other tables in Highway
Statistics, but are included here for the user's convenience.
Finally, additional special considerations that the user should
be aware of in using the information in Highway Statistics
are included in the discussion that precedes each of the individual