The Importance of Highways to U.S. Agriculture


In December 2020, USDA released a report, The Importance of Highways to U.S. Agriculture, to examine the importance of highway infrastructure to the efficient movement of domestic agricultural products. The agriculture industry is the largest user of highway freight, and the industry relies on highway infrastructure for the safe and efficient transportation of goods. The report’s analysis showed that 80 percent of domestic agricultural commodities travel on 17 percent of the U.S. highway mileage. These “High-Volume Domestic Agriculture Highways” (HDAH) are important to U.S. farmers, the agriculture industry, and downstream producers. The report utilized a novel analysis technique to combine and geo-reference public and proprietary data sets to project roadway conditions on 17 HDAH corridors. This section provides further context and detail to the data that can be publicly shared and the methodology behind them. For more information, please see the full report.
The series of maps and charts below show commodity flows on key highway segments and the condition and performance of select highway corridors. This additional data is presented to help transportation planning entities benefit from understanding how domestic agricultural commodities move on U.S. highways, and how highway condition and performance of highways may affect those movements.

High Volume Domestic Agricultural Highways 

This section identifies high-volume domestic agriculture highways (HDAH) that moved the largest volumes of U.S. agricultural freight in 2018 using the IHS Markit Transearch database. This dataset is similar to the U.S. Census Commodity Flow Survey and the Federal Highway Administration's (FHWA) Freight Analysis Framework, but provides greater spatial and commodity-level resolution. HDAH connect high-producing agricultural areas with storage, processors, ports, other transportation modes, and more. The agricultural commodity flows along the HDAH comprise approximately 805 million tons and represent over $428 billion in market value.
The HDAH consist of just over 49,000 highway miles of both Interstates and non-interstates. They carry the top 80 percent of the tonnage or market value of the focus commodities (fruits, vegetables, grain, dairy, livestock, and poultry) produced in the United States and represent approximately 17 percent of the lane mileage of the network of highways modeled in the Transearch database.
The first map below shows how HDAH connect areas where key agricultural products are produced in high volumes, based on 2017 production of the focus commodities which serve as a representative sample. The next two maps show the movement of the focus commodities along the HDAH by volume and value.

Seventeen Analysis Corridors

This section analyzes 17 corridors within the HDAH in greater detail to illustrate how specific agricultural commodities move through the HDAH, and the congestion, reliability, and safety performance characteristics of these corridors. The corridor analysis approach allows examination of the characteristics and performance of significant HDAH corridors in a detailed way that is not possible for all HDAH because of data and resource limitations. In many cases, agricultural freight does not regularly travel the corridors’ full length, but we can better understand a corridor’s importance by examining the variations in commodity flow and performance along the corridor.
The analysis corridors were chosen by identifying the top 5 percent of routes within the HDAH that carry the largest share of each of the focus agricultural commodities (by tonnage, market value, or truck units) and matching this to corresponding performance data from the Highway Performance Monitoring System (HPMS) and National Performance Monitoring Research Data Set (NPMRDS). Corridor endpoints were chosen using natural breaks in the commodity flow data and comparison with highway infrastructure and relevant intermodal and processing facilities. Additional corridors that fell just shy of the 5-percent threshold were added to ensure a geographic balance and incorporate insights from the stakeholder engagement element of the project.
The first map below shows the 17 analysis corridors, and the maps that follow show commodity flows along the 17 corridors by tons, value, and truck units.

Map of Seventeen Analysis Corridors

Performance Metrics Along Key Corridors

This section analyzes the performance of 17 key corridors in terms of pavement and bridge condition, congestion, reliability, and safety. The first chart shows the average annual daily traffic for the 17 corridors, while the charts that follow show the travel time index (TTI), truck travel time reliability index (TTTR), and the bridge and pavement conditions for the 17 corridors. TTI indicates the level of congestion, while TTTR shows how consistent congestion levels vary over time.