Transportation Infrastructure

The International Roughness Index is used worldwide to measure whether travelers experience a rough or a smooth ride while driving on a highway. The index is a quantitative measure of a vehicle's up-and-down movement while traveling. States collect and report data to the Department of Transportation (DOT). This report describes (1) the uses DOT's Federal Highway Administration (FHWA), the states, and others make of the index to assess highway conditions; (2) the consistency and accuracy of state-reported data on highway roughness; and (3) FHWA's efforts to improve the data across states.

GAO noted that: (1) the International Roughness Index is used widely for federal and state purposes, as well as for independent analyses; (2) at the national level, where the index is the only available statistic on pavement conditions, FHwA uses it to assess changes in the overall condition of the nation's highways and to forecast future highway investment needs; (3) actual expenditures for highways by all levels of government in 1995 were about $29.2 billion, or about $41 billion less than FHwA had projected as needed to repair the deficiencies; (4) in addition, FHwA uses the index to measure progress toward a goal for ride quality in its strategic plan and publishes data from the index for use by the public; (5) at the state level, where other types of data on pavement conditions are available, reliance on the index varies; (6) while some states rely on it to make highway maintenance decisions, others do not consider it an important decision-making tool; (7) the states that rely on the index use it to project highway investment needs and report on pavement performance at the state or district levels; (8) in addition, some states use the index to set standards for construction projects; (9) independent analysts have used the data to compare pavement conditions across states and to develop scorecards of state performance; (10) critics contend that state comparisons based on the index are flawed because the pavement roughness data reported to FHwA by the states are not consistent or accurate; (11) these problems with consistency and accuracy have occurred for two reasons: (a) the states use different methods to gather data and compute results; the states differ in the devices they use to measure the pavement, the part of the road they measure, and their choice of an appropriate mathematical simulation; and (b) the type of surface asphalt or concrete influences the results; concrete roads may produce rougher readings than asphalt roads, even if the concrete road is of very high quality; (12) features such as joints between sections can contribute to the roughness of concrete highways; (13) while FHwA has tried to improve the data, these efforts have not been completely successful; and (14) the agency developed detailed guidelines for collecting the data and asked the states to apply these guidelines before reporting the data.

Recommendations

Our recommendations from this work are listed below with a Contact for more information. Status will change from "In process" to "Open," "Closed - implemented," or "Closed - not implemented" based on our follow up work.

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