The Federal Highway Administration Highway Performance Monitoring System is the national database for US roadway conditions—collecting pavement condition ratings, traffic volumes, lane miles, and functional class data for 4.1 million miles of public roads, from Interstate highways to rural local roads, enabling Congress to calculate federal highway funding formulas and researchers to track infrastructure decline.
What HPMS is and why it exists
The Highway Performance Monitoring System was established in 1978 following the Federal-Aid Highway Act, which directed FHWA to maintain a systematic national database of highway conditions and performance. The program is administered by the FHWA Office of Highway Policy Information and operates through annual data submissions from each of the 50 state departments of transportation, the District of Columbia, and US territories. States collect field data on pavement condition, traffic volumes, geometric characteristics, and operational attributes throughout the year and submit their HPMS data to FHWA in June of the following year.
The legal anchor for HPMS is 23 USC 502, which mandates that FHWA produce a biennial Conditions and Performance Report to Congress—the C&P Report—assessing the current status and future investment needs of the US highway and bridge network. Every C&P Report draws directly on HPMS data for its pavement condition and performance findings. The most recent reports cover the full NHS and provide projections of investment needed to maintain or improve current conditions under different funding scenarios. Congress uses this evidence base when authorizing surface transportation legislation and setting funding allocation formulas.
HPMS also functions as the data foundation for the federal-aid highway program funding formulas. The apportionment of formula funds among states under programs such as the National Highway Performance Program depends partly on lane-mile counts, VMT, and pavement condition data that states report through HPMS. States that report inaccurate or incomplete HPMS data may receive incorrect apportionments, which gives state DOTs strong institutional incentives to maintain high-quality submissions.
Coverage within HPMS is tiered by road classification. For the National Highway System and other federal-aid highways, states must submit full-extent coverage—data for every section of roadway in those functional classes. For minor collectors and local roads, HPMS uses a sample-based approach: states submit data for a statistically designed sample of sections sufficient to produce reliable statewide estimates. FHWA uses the sample data to generate national and state-level estimates for the full lower-classified road network without requiring field measurement of every local street and rural road in the country.
The scale of the US road network
The total US public road network covered by HPMS comprises approximately 4.1 million centerline miles. That figure encompasses every public road from the Interstate highway system down to the shortest paved local street maintained by a county or municipality. Understanding the scale and composition of that network is essential context for interpreting HPMS data.
The Interstate Highway System, completed as a connected network in the 1990s, covers approximately 48,000 miles of divided limited-access highway. Despite representing barely more than one percent of total public road mileage, the Interstate carries a disproportionate share of national traffic—roughly 25 percent of all vehicle miles traveled—because it serves the highest-volume urban and intercity corridors. The National Highway System, established by Congress in 1995, is a broader designation that includes the Interstate plus other highways of national significance: principal arterials connecting major urban areas, Strategic Highway Network routes used for defense mobilization, and intermodal connectors linking ports, rail terminals, and airports to the NHS backbone. The NHS totals approximately 163,000 centerline miles.
Federal-aid highways—those eligible for federal highway funding and subject to federal geometric and design standards—total roughly 1.1 million miles. This category covers the NHS plus other principal arterials, minor arterials, and collectors that carry most of the country's non-local traffic. The remaining approximately 3 million miles of public roads are local roads: streets in residential subdivisions, rural county roads, and municipal streets that carry local access traffic. Local roads are the largest category by mileage but carry a small fraction of total VMT.
A critical distinction in HPMS data is between centerline miles and lane miles. A four-lane divided highway has one centerline mile per physical mile of road but four lane miles, because lane miles count each travel lane separately. The Interstate system's 48,000 centerline miles translate to roughly 115,000 lane miles once the multiple lanes of divided highway are counted. Lane miles matter for pavement condition reporting because pavement measurements are taken by lane, and funding formulas that reference lane miles capture the actual pavement area requiring maintenance rather than simply counting road centerlines.
The rural versus urban split in the US road network is striking. By centerline miles, approximately 75 percent of public roads are rural—reflecting the vast geographic extent of the country outside metropolitan areas. By vehicle miles traveled, however, the distribution inverts: roughly 60 percent of VMT occurs on urban roads, which carry high traffic volumes on comparatively short segments. This inversion shapes funding and condition debates: rural roads dominate the mileage count but urban roads experience more intensive use-related deterioration and serve more vehicle trips per mile of road.
Bridge data is tracked separately from HPMS through the National Bridge Inventory, a companion FHWA database covering approximately 620,000 bridge structures. While NBI and HPMS share the same institutional home at FHWA and both feed into the C&P Report, they are distinct data systems with different collection methodologies, reporting cycles, and data structures. The NBI records bridge-specific condition inspections on a 24-month cycle; HPMS records pavement and traffic data across road sections on an annual cycle.
Pavement condition data and the International Roughness Index
The central pavement condition metric in HPMS is the International Roughness Index. IRI measures road surface smoothness by quantifying the accumulated vertical displacement of a vehicle suspension as it travels along a road surface, expressed in inches per mile (or meters per kilometer in the international standard). A lower IRI indicates a smoother road surface; a higher IRI indicates a rougher surface with more significant surface irregularities. IRI is measured using inertial profilers—laser-based instruments mounted on vehicles that travel at highway speed and record the road profile continuously.
FHWA establishes IRI thresholds for classifying pavement condition on the NHS into the Good, Fair, and Poor categories used in the C&P Report and in performance management reporting. For Interstate highways, the thresholds are: Good if IRI is below 95 inches per mile, Fair if IRI is between 95 and 170 inches per mile, and Poor if IRI exceeds 170 inches per mile. For non-Interstate NHS roads, the thresholds are slightly higher to reflect different design standards and use conditions. A freshly paved Interstate highway typically measures IRI values in the range of 40 to 60 inches per mile; roads at the Poor threshold of 170 inches per mile produce a noticeably rough ride that most drivers would describe as uncomfortable at highway speed.
IRI was not always the primary pavement condition metric in federal reporting. Before the widespread adoption of IRI measurement in the 1990s, HPMS relied on the Present Serviceability Rating, a subjective rating scale developed in the 1950s through the AASHO Road Test. PSR ranged from 0 to 5 and was derived from a combination of physical measurements and rater assessments. The transition to IRI provided an objective, instrument-measured standard that is reproducible across states and over time, which significantly improved the comparability of pavement condition data across the national inventory. PSR is still referenced in some state DOT systems and historical datasets but is no longer the primary federal reporting metric.
HPMS collects several additional pavement distress indicators beyond IRI. Cracking percentage measures the fraction of pavement area showing visible cracking, a distress mode that indicates structural deterioration in flexible (asphalt) pavements and joint deterioration in rigid (concrete) pavements. Rutting depth measures the longitudinal depression formed in asphalt pavement under repeated wheel loading—rutting is a safety concern because it channels water and can cause vehicle instability in wet conditions. Faulting measures the vertical offset at joints or cracks in concrete pavement, a condition that produces the characteristic “bump” at pavement joints and accelerates roughness progression. Together, IRI, cracking, rutting, and faulting provide a multi-dimensional picture of pavement condition that goes beyond the single-number smoothness index.
State DOTs also use the Pavement Condition Index, a 0-to-100 composite distress rating developed by the US Army Corps of Engineers. PCI incorporates visual distress survey data across a wider range of distress types than HPMS collects and is widely used by state and local agencies for network-level pavement management systems. PCI is not reported directly in HPMS—it is not part of the FHWA national data specification—but many state DOTs maintain PCI alongside their HPMS data as part of their own pavement management programs. Researchers and state agencies sometimes use PCI to cross-validate HPMS IRI-based condition classifications.
One significant source of variation in HPMS pavement data is equipment differences among states. While FHWA mandates IRI as the metric and requires the use of certified inertial profilers, the specific equipment, calibration procedures, and measurement protocols vary across state DOT fleets. This variation introduces known systematic differences in reported IRI values that complicate direct state-to-state comparisons. FHWA has implemented profiler calibration requirements and proficiency testing programs to reduce these differences, but analysts working with HPMS data across states should be aware that apparent condition differences between states may partly reflect measurement system variation rather than true pavement condition differences.
Traffic data: AADT, VMT, and the Traffic Volume Trends
HPMS is as much a traffic database as a pavement condition database. Every HPMS section record includes traffic data characterizing the volume and composition of vehicles using that road section. The primary traffic metric is the Annual Average Daily Traffic— the estimated average number of vehicles crossing a point on the road on any given day of the year, averaged across all 365 days including weekends and seasonal variation. AADT is derived from continuous count stations supplemented by short-duration traffic count programs that states operate throughout their road networks.
Vehicle Miles Traveled is the aggregate measure computed from AADT data across all HPMS sections. VMT for a road section equals AADT multiplied by section length; summing across all sections in the national network yields total national VMT. VMT is the traffic metric that drives emissions inventories, economic analyses of transportation demand, and several federal highway funding formula components. The Federal Highway Trust Fund, which receives most of its revenue from the federal motor fuel tax of 18.4 cents per gallon of gasoline and 24.4 cents per gallon of diesel, is directly linked to fuel consumption—and fuel consumption, adjusted for fuel economy trends, tracks VMT.
Published FHWA data on annual VMT shows long-run growth interrupted by two major disruptions in recent decades. VMT grew steadily from approximately 3.095 trillion miles in 2015 to 3.261 trillion miles in 2019. The COVID-19 pandemic caused an unprecedented single-year decline: 2020 VMT fell to 2.905 trillion miles, a drop of approximately 11 percent, as shelter-in-place orders, remote work adoption, and business closures sharply reduced vehicle travel. VMT recovered rapidly in 2021 to 3.181 trillion miles and stabilized near pre-pandemic levels in 2022 at approximately 3.192 trillion miles. The 2022 figure remained slightly below the 2019 peak, with persistent remote work keeping commute VMT below pre-pandemic levels in many metropolitan areas even as leisure and freight travel recovered fully.
Truck VMT is tracked separately within HPMS and through FHWA's Freight Analysis Framework. Commercial truck traffic imposes disproportionate pavement damage relative to passenger vehicles because pavement wear scales roughly with the fourth power of axle load—a loaded 80,000-pound semi-truck causes approximately 10,000 times more pavement damage per pass than a typical passenger car. Interstate highways and major arterials in freight corridors experience accelerated pavement deterioration driven by truck traffic that their IRI measurements directly reflect.
Alongside annual HPMS data, FHWA publishes the Traffic Volume Trends report monthly, providing early estimates of current VMT based on a sample of continuous traffic count stations. TVT data is released approximately 60 days after the end of each month and provides the first available indication of national travel trends before the full HPMS annual data cycle is completed. TVT is the source cited in news coverage of monthly travel demand changes, including the COVID-era travel collapse and subsequent recovery.
Infrastructure funding: IIJA, NHPP, and performance management
The Infrastructure Investment and Jobs Act of 2021—the Bipartisan Infrastructure Law—directed $110 billion specifically for roads and bridges over five fiscal years (2022 through 2026), the largest dedicated road and bridge investment in US history. Within that total, multiple program structures channel funds toward pavement condition improvement in ways tied directly to HPMS data.
The National Highway Performance Program is the largest formula program in surface transportation funding, providing approximately $29 billion per year to states for the construction, reconstruction, and preservation of highways on the NHS. NHPP funds can be used for pavement rehabilitation, bridge replacement, safety improvements, and capacity expansion on NHS routes. Under the performance management framework established by MAP-21 in 2012 and reinforced by the FAST Act and IIJA, states must set two-year and four-year targets for NHS pavement condition using the IRI, cracking, rutting, and faulting metrics collected through HPMS. FHWA monitors state progress against these targets using HPMS data.
The performance management consequence for states that report poor NHS pavement condition and a deteriorating trend is substantial. Under 23 CFR Part 490, if a state reports that more than 5 percent of Interstate lane-miles are in Poor condition and fails to demonstrate progress toward improvement, FHWA can impose a spending restriction requiring the state to direct a portion of its NHPP funds specifically toward Interstate pavement improvement rather than allowing discretionary allocation among eligible projects. This mechanism gives HPMS pavement condition data direct budget consequences for state DOTs and is a significant enforcement lever in the federal-aid highway system.
The IIJA also created the new Bridge Formula Program ($27.5 billion) and the Promoting Resilient Operations for Transformative, Efficient, and Cost-saving Transportation program (PROTECT, $8.7 billion), which funds resilience improvements to transportation infrastructure against climate hazards including flooding, extreme heat, and wildfire. Road pavement is vulnerable to heat damage—high summer temperatures cause asphalt softening and accelerated rutting—and HPMS rutting data in regions with increasing extreme heat events is becoming relevant to climate resilience analysis. The Good Repair formula program specifically targets deferred maintenance on federal-aid highways, providing funding for rehabilitation projects on routes where deferred maintenance has allowed condition to deteriorate below the thresholds that more expensive reconstruction would otherwise require.
The MAP-21 performance management framework that governs NHS pavement condition targets operates through a cycle of state-set targets, FHWA monitoring, and annual progress determination. States submit targets in the form of percentage-of-lane-miles in Good and Poor condition by fiscal year. FHWA compares the annual HPMS data to those targets and publishes determination letters indicating whether states are making significant progress. The target-setting and monitoring process is fully documented in FHWA's pavement performance management regulations and has created an extensive public record of state pavement condition commitments and outcomes.
State of the roads: 2022 C&P Report findings
The 2022 Conditions and Performance Report to Congress presents the most comprehensive recent assessment of US highway network condition available from HPMS data. Its findings on pavement condition reflect a network that has seen incremental improvement in some categories alongside persistent deterioration in others, particularly on urban routes and in states with aging infrastructure and constrained transportation budgets.
For the Interstate system, the 2022 C&P data shows approximately 43 percent of Interstate lane-miles in Good condition (IRI below 95 inches per mile) and approximately 6 percent in Poor condition (IRI above 170 inches per mile). Urban Interstates consistently show worse IRI than rural Interstates—a pattern driven by higher traffic intensity, more truck loading, and the greater complexity of pavement maintenance operations in urban environments where lane closures impose significant traffic management costs. Non-Interstate NHS routes show somewhat lower Good percentages and higher Poor percentages than the Interstate, reflecting lower relative investment and the inclusion of urban arterials with challenging maintenance environments.
Pavement deterioration accelerated during the COVID-19 pandemic years in ways that HPMS data captures clearly. The sharp VMT decline of 2020 initially appeared to suggest that reduced traffic loading might arrest or slow pavement deterioration. In practice, state DOT maintenance operations were also disrupted by budget pressures, workforce constraints, and supply chain problems during the pandemic period. Deferred maintenance during 2020 and 2021 contributed to condition decline in states where preventive maintenance programs were suspended, and the recovery of heavy truck traffic to pre-pandemic levels by late 2020 continued to load pavement sections that had received reduced maintenance attention.
The bridge condition picture tracked separately through the National Bridge Inventory shows approximately 42,000 structurally deficient bridges—roughly 7 percent of the 620,000-structure national inventory. While this represents significant improvement from the 22 percent structurally deficient rate of the early 1990s, the remaining population of deficient bridges includes structures carrying millions of vehicle crossings daily. The American Society of Civil Engineers' 2021 Infrastructure Report Card assigned roads a grade of C-minus, citing the combination of pavement condition deterioration, bridge deficiency, and a deferred maintenance backlog the ASCE estimates at approximately $1.3 trillion across the combined road and bridge network.
The deferred maintenance concept is central to interpreting HPMS condition data in a funding context. Pavement maintenance economics follow a well-documented curve: preventive maintenance actions performed while a pavement is in Good condition are substantially less expensive per lane-mile than rehabilitation of a pavement that has deteriorated into Fair condition, which in turn is far less expensive than full reconstruction of a pavement that has reached Poor condition and begun to fail structurally. The HPMS data, by tracking pavement sections across the Good-Fair-Poor progression annually, provides the empirical input for estimating how much deferred maintenance has accumulated and what investment would be required to reverse the trend.
Data access and the HPMS Field Manual
HPMS data is compiled at the national level and released through several FHWA publication channels. The primary public release is the HPMS Public Release dataset, available through the FHWA data portal at maps.dot.gov/HPMS. The public release includes section-level records with pavement condition, traffic, and geometric attributes for NHS and federal-aid routes, available in GeoJSON and shapefile formats for GIS analysis. The spatial format of the public release enables mapping and geographic analysis of pavement condition patterns across the national road network.
The HPMS Field Manual, published by FHWA, is the authoritative reference for the data specifications, field definitions, acceptable values, and quality control requirements that govern state submissions. The Field Manual defines the data elements that states must report for each functional class tier, the measurement methodologies for pavement condition metrics, and the sample design requirements for lower-classified roads. Analysts working with HPMS data should treat the Field Manual as the primary technical reference, as it contains the precise definitions needed to correctly interpret what the data elements represent and what measurement protocols generated the reported values.
For summary statistics and trend data, the FHWA Highway Statistics publication series at fhwa.dot.gov/policyinformation/statistics provides annual tabulations covering road mileage by functional system, pavement condition by state, VMT by road class and state, and bridge condition summaries. The Highway Statistics tables are published as Excel and PDF files and provide the published summary figures cited in the C&P Report and in most infrastructure policy analyses. Table HM-64 covers pavement condition on the NHS by functional system and state; Table VM-2 covers VMT by functional system; Table HM-20 covers road mileage by functional system and ownership.
The FHWA Traffic Volume Trends monthly publication at fhwa.dot.gov/policyinformation/travel_monitoring/tvt.cfm provides monthly VMT estimates based on the continuous traffic count station network. TVT data is available as monthly PDF reports and as tabular data files. It is the earliest available indicator of changes in national travel demand and is widely used by transportation economists, energy analysts, and policy researchers who need timely VMT data rather than waiting for the annual HPMS cycle.
Direct programmatic access to HPMS section-level data is more limited than for some other federal transportation datasets. There is no comprehensive REST API for HPMS comparable to the BTS Transtats API for airline data or the NHTSA FARS API for crash records. The HPMS public release data portal provides visualization tools and download interfaces but does not expose a queryable API for arbitrary section-level data extraction. Researchers requiring full section-level data for a state or the national network typically work with the bulk GeoJSON or shapefile downloads from the HPMS portal rather than a programmatic API.
Python: analyzing FHWA pavement condition summary data
The following Python script demonstrates working with published FHWA HPMS summary statistics and VMT data. Because the HPMS section-level public release is distributed as bulk geospatial files rather than a queryable API, most research workflows start with the published summary tables from the Highway Statistics series or the C&P Report appendices. The script constructs a representative HPMS pavement condition summary from the 2022 C&P Report data and analyzes the VMT time series from published FHWA Traffic Volume Trends data.
import requests, pandas as pd
# FHWA Highway Statistics — published tables (CSV/Excel format)
# Table HM-64: Pavement condition on the NHS by functional system
# Published at: https://www.fhwa.dot.gov/policyinformation/statistics/2022/
# FHWA Traffic Volume Trends — monthly VMT data
vtt_url = "https://www.fhwa.dot.gov/policyinformation/travel_monitoring/tvt.cfm"
print("FHWA Traffic Volume Trends available at:", vtt_url)
# HPMS national summary data (example from published C&P Report appendix)
# These figures are from the 2022 Conditions and Performance Report
hpms_summary = {
"Functional System": [
"Interstate", "Other NHS", "Other Principal Arterial",
"Minor Arterial", "Collectors", "Local"
],
"Lane Miles (thousands)": [115, 261, 317, 420, 780, 2200],
"Pct Good IRI": [43, 38, 35, 30, 28, None],
"Pct Poor IRI": [6, 9, 12, 15, 18, None],
"AADT (avg)": [28500, 15200, 8700, 4200, 1800, 500],
}
df = pd.DataFrame(hpms_summary)
print("\nHPMS 2022 Pavement Condition Summary (National Highway System):")
print(df.to_string(index=False))
# VMT by year (published FHWA data)
vmt_data = {
"Year": [2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022],
"VMT_trillion": [3.095, 3.174, 3.212, 3.226, 3.261, 2.905, 3.181, 3.192],
}
vmt_df = pd.DataFrame(vmt_data)
print("\nUS Vehicle Miles Traveled by Year (trillions):")
print(vmt_df.to_string(index=False))
pct_change = ((vmt_df['VMT_trillion'].iloc[-1] / vmt_df['VMT_trillion'].iloc[-2]) - 1) * 100
print(f"2021-2022 change: {pct_change:+.1f}%")
The pavement condition summary illustrates the structural pattern that HPMS data consistently reveals: Good condition percentages decline as functional class drops from Interstate to collector, while Poor condition percentages increase. The Interstate benefits from concentrated federal investment, higher design standards, and the performance management framework that imposes spending restrictions when Poor condition exceeds 5 percent of lane-miles. Non-Interstate NHS routes and off-system collectors receive less targeted federal oversight and tend to show wider variation in condition across states depending on state DOT investment priorities.
The VMT time series makes the COVID disruption visible quantitatively: the 2020 reading of 2.905 trillion miles is the largest single-year VMT decline in the FHWA data record going back to the 1970s. The rapid 2021 recovery—a gain of approximately 9.5 percent in a single year—was itself nearly unprecedented, driven by pent-up travel demand, economic reopening, and the resumption of commuting as employers called workers back. The 2022 stabilization near but below the 2019 peak reflects the structural shift in commute patterns associated with hybrid and remote work arrangements that persisted well beyond the acute phase of the pandemic.
For more granular state-level analysis, the Highway Statistics Table HM-64 provides pavement condition data by state and functional system in Excel format, enabling comparison of Good and Poor IRI percentages across all 50 states for each road class. States with the highest Poor IRI percentages on the Interstate tend to be those with the oldest Interstate infrastructure—built in the 1950s and 1960s during the original National System of Interstate and Defense Highways construction—and those that have faced sustained budget constraints limiting preventive maintenance investment. Pairing HM-64 data with state DOT budget data from the Highway Statistics Table SF-1 (state highway agency receipts) provides a quantitative basis for analyzing the relationship between transportation investment levels and pavement condition outcomes across states.