State-by-State Analysis

Because of the differences in State data reporting, FHWA evaluates and adjusts the data submitted by the States. FHWA's State-by-State analysis is a detailed process, requiring completion of four worksheets for each State, plus additional calculations in some situations. It is important to note once again, that the purpose of this process is to attribute to each State its proportion of on-highway motor fuel usage. This attribution of gallons is based on State tax information. To obtain equal treatment of all States, adjustments are made to the State reports to account for unequal reporting of off-highway uses, public uses, and differences in definitions of gasohol.

The first step in the FHWA annual analysis of a State's data is to run a summary program of the monthly FHWA-551M reports for a calendar year. [The State annual summary report (FHWA-556) is for a State's fiscal year, which may be on a calendar basis or may be on some other annual basis.] Using this calendar year summary, FHWA compares the annual summary totals based on FHWA-551M monthly reports with the preliminary estimates provided through the nationwide models for non-highway fuel use, public fuel use, and gasohol consumption.

From the gross gallons reported, FHWA subtracts the gallons of gasoline listed as exempt or refunded for off-highway purposes or exported to other States and the gallons of diesel listed as non-highway, public (except transit), and exported. (There has been a change regarding reporting of public diesel usage. More information is provided in the section on "Process Refinements.") FHWA also examines motor fuel loss allowances. (There has been a change regarding reportable losses. More information is provided in the section on "Process Refinements.") Because IFTA data are available on a quarterly rather than a monthly basis, some months will contain "spikes." In addition some States do not report IFTA gallons on FHWA-551M; the missing IFTA data may be on FHWA-556, or the data may be on supplementary documents. (FHWA will be providing additional guidance on reporting IFTA data.)

Form FHWA-556 serves as a checkpoint for the time period covered by the State's fiscal year. It is used to compare State-reported revenue against State-reported gallons multiplied by the State's tax rate. Some States have very complicated tax structures and require additional special attention.

Generally, State motor-fuel taxes are levied on all consumers, and refunds of the taxes paid or exemptions to the tax are given for non-highway use of motor fuel. However, not all States offer refunds or exemptions for all classes of non-highway use, and not all available refunds are actually claimed. Thus, often the net volume of fuel taxed is not the same as the volume consumed on highways. Volume of motor fuel consumed on the highways in each State is the primary data parameter of interest for FHWA purposes. Therefore, various adjustments to the tax-status information provided by the States are needed to treat States equitably.

By FHWA definition, transit use, regardless of the ownership of the transit system, is treated as private and commercial use of special fuels. Many States do not report their use of transit special fuels. Transit motor fuel use is available on the Federal Transit Administration web site, and States may use this data if they wish.

Aviation gasoline is another fuel tracked by an independent source. Since aviation gasoline is treated differently than normal gasoline, the U. S. Department of Energy (DOE), Energy Information Agency, tracks its inventory. FHWA uses this source along with estimation procedures for determining the stock of aviation gasoline in a State.

While intrastate diesel fuel use is captured under normal State reporting procedures, interstate use is covered under IFTA procedures. Almost all States and Canadian Provinces now use IFTA provisions. (The Yukon, Alaska, and Hawaii are the exceptions.) IFTA taxation addresses the issue of where the fuel is used, rather than where it is purchased. IFTA measures the use of diesel, gasoline, gasohol, and other special fuels. A problem with IFTA data is the reporting lag. IFTA processing takes place on a quarterly basis and a State does not know its IFTA net tax revenue until five to six months after tax liability occurs. Current FHWA guidance asks for State data within 90 days of the end of the reporting month.

At this point in the attribution process, the State's data will have been separated into use (on-highway versus off-highway), fuel type (gasoline, gasohol, special fuels), and tax status based on public, private, and commercial categories (exempt, refunded, taxed-at-other-rate, etc.). As a final step, FHWA sums the on-highway gallons to derive a national total for each of the three motor fuel types and divides each State's gallons by the total gallons. This percentage is the State's share. For the Federal truck tax revenue, each State's share of special fuels is used to calculate attribution. This analysis is documented in a draft data report, issued about eight months after the end of the calendar year being reported. States and the FHWA work together to review and modify the report as needed. The final version is issued around August, about 20 months following the calendar year being reported.

In summary, the attribution process estimates the gallons of motor fuel used on-highway in each State. The process uses data reported by the States, develops estimates for unreported data, and adjusts the data based on consistent definitions. The methodology is sound. However, improvements in data uniformity, accuracy, and consistency would ensure that each State receives its share, consistent with Congressional intent. FHWA proposes to provide improvements in instructions (e.g., a revised Guide to Reporting Highway Statistics) and other documentation (e.g., IFTA reporting description and a description of FHWA models and analyses). The purpose of these documentation improvements is to assist the States in reporting their data.

A flow chart showing the basic steps in the attribution process is shown on the following page. The boxes on this chart represent actual tables of data; the ovals are steps in the analysis process as described above. Titles of the tables (e.g., MF-1) shown in the chart are provided in the table below the chart.

Flow Chart of Motor Fuel Data


Titles of Tables Used In "Flow Chart of Motor Fuel Data"


Table Title


Monthly Motor Fuel Information



Special fuels reported by States



Gasoline and gasohol reported by States



State tax rates on motor fuel


General State Motor Fuel Information


  State motor fuel taxes and related receipts


  Motor fuel volume taxed


  Motor fuel use


  Non-highway use of gasoline


Attribution Tables

  Highway use of motor fuel
  Estimated use of gasohol
  Receipts attributable to highway users by State
  Comparison of receipts to apportionments and allocations
  Selected data used in apportionments



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