Overall, the 1958-1960 AASHO Road Test encompassed the largest & most substantive pavement research performed in the 20th century. Its results have proven to be highly influential with respect to highway design & construction. FHWA: It is a landmark in highway & bridge design that has never been equaled.
“ASSHO Road Test of 1958-1960”. Click to enlarge.
1958 Ribbon Cutting Launching Ceremony:
The inaugural ceremony for the American Association of State Highway Officials (AASHO) Road Test took place October 15, 1958—in Ottawa, Illinois, southwest of Chicago. The AASHO Road Test was conducted in the North Central region, on the future alignment of I-80 near Ottawa, Illinois (Figure 10 above), and played an important role in the design of Interstate pavements.
The noon ceremony officially launched the comprehensive project with a ribbon cutting by Illinois Governor William G. Stratton. Speaker Ellis L. Armstrong, Commissioner-BPR (recently appointed) proclaimed to those in attendance,
“Today we are opening the most important section of highway in the country. For highways are built for only one reason: TO SERVE THE PEOPLE! And this road is not different in that respect . . . . The benefits from this test road . . . will begin to serve the Nation at the earliest possible date.”
Claude R. McMillan, President-AASHO and Chief Highway Commissioner-South Carolina, likewise spoke at the ceremony. He asserted, “This is a big day for highway transportation in the United States and everywhere.”
Sponsored by AASHO and administered by the Highway Research Board (now Transportation Research Board (TRB)) of the National Academy of Sciences), the purpose of the AASHO Road Test entailed conducting scientific studies of the performance of highway pavements when subjected to repeated passages of vehicles of various weights and sizes. According to the Federal Highway Administration (FHWA), the test site was financed by:
• State highway agencies • U.S. Bureau of Public Roads (BPR) • Department of Defense (DOD)—provided heavy vehicles and drivers • Automobile Manufacturers Association • American Petroleum Institute • American Institute of Steel Construction • Federal-aid highway funds • American materials and transportation associations • Foreign countries
1956 to 1958: Construction
In August 1956, construction of the 7-mile two-lane pavements began—the future alignment of I-80 near Ottawa, Illinois—and consisted of 6 loops and a tangent: half concrete/half asphalt.
Click to enlarge. 6 Pavement Loops in AASHO Road Test.
6 pavement loops comprised the Test Road:
• 5 loops were exposed to traffic loadings (Figure 11 above)
• Each traffic loop consisted of two straight tangent sections and a super-elevated turnaround connecting them at each end
• Tangent lengths were
—6,800 ft for Loops 3 – 6
—4,400 ft for Loop 2
—2,000 ft in Loop 1
• 2 traffic lanes were constructed throughout the large loops
• Each lane in traffic loops subjected to specific truck axle type and axle load
• Northern tangent section and the eastern turnaround of each loop consisted of HMA test sections
• Southern tangent section and the western turnaround of each loop consisted of PCC test sections
• Series of short test sections were constructed within each tangent (representing a factorial set of pavement thicknesses), separated by a short transition
• Each test section was separated into two identical pavement sections by the centerline of the pavement (as specific truck axle type/axle load combinations operated in each lane)
• 16 short-span bridges
• Total: 836 test sections constructed in all loops at the AASHO Road Test:
—468 HMA pavement test sections
—368 PCC pavement test sections
1958 to 1960: Testing
The AASHO Road Test was conducted between 1958 and 1960, and ended November 30, 1960. The performance of the pavement sections were closely monitored over the 2-year period. The Road Test employed a wide range of surface, base, and subbase thicknesses, and:
• Evaluated the performance and behavior of pavement structures under a variety of axle loadings
• Investigated the performance of highway bridge structures under known loading conditions—provided the foundation for analytical evaluation of stresses and deflections from moving vehicles
The U.S. DOD provided cars and heavy-duty trucks that were driven over this experimental stretch of highway relentlessly to see which pavement segments lasted the longest in the best possible condition. Information on these segments was crucial in advancing knowledge about structural design, pavement performance, and the impact of heavy loads.
The AASHO Road Test was one of the most significant pavement research projects conducted in the past 50 years:
• Pavement construction and monitoring, and data analysis activities conducted established many standards and protocols and helped define design, construction, and evaluation practices.
• Even now, 6 decades after the completion of the Road Test, the AASHO (now AASHTO) design procedures continue to serve as the cornerstone for both PCC and HMA pavement design in the United States and other countries.
• Additionally, data from the Road Test are often used by researchers in a variety of ways unforeseen by the original AASHO Road Test developers.
• According to the FHWA, the design of pavements and bridges on the Interstate System largely followed the results of the AASHO Road Test.
• The test data established the relationships for pavement structural designs based on expected loadings over the life of a pavement.
• A portion of the original AASHO Road Test sections (Loop 1, the untrafficked loop) still remains today in the right-of-way of I-80 as a visible reminder of the significant contributions of the Road Test.
1962
The results of the AASHO Road Test were used in the development of the interim pavement design procedures that were released to the states in 1962 for a 1-year trial usage. The design procedures were widely accepted by many highway agencies and were used to design many of the pavements constructed during the Interstate era.
Overall, the 1958-1960 AASHO Road Test encompassed the largest & most substantive pavement research performed in the 20th century. Its results have proven to be highly influential with respect to highway design & construction. FHWA: It is a landmark in highway & bridge design that has never been equaled.
Click to enlarge
Early 20th Century:
This effort was far from being the first one undertaken to assess the most optimal materials and designs for the development of long-lasting roads.
1922: An early and well-documented example of this type of test involved the 2.5-mile (4-kilometer) test segment of Bates Experimental Road in Springfield Illinois by the Illinois Division of Highways. It was to determine the best materials to use for rural roads carrying major truck traffic and concluded that concrete was the best material for highway building and provided a precise design to maximize the life of concrete roads. Please see the ISCP October article: www.concretepavements.org/2020/10/29/influential-1920s-road-test-conducted-in-illinois/
1930s & 1948: The U.S. Bureau of Public Roads (BPR) conducted several loading tests on concrete pavement during the 1930s. Systematic efforts to gauge the service life of highway pavements and the impact of wheel loads gained new momentum after World War II. AASHO provided strong leadership and support when it came to those efforts. In 1948, the association established formal procedures for launching and managing road tests. These research projects were financed jointly by two or more states to provide data for the development of longer-lasting pavements to handle ever-increasing traffic nationwide.
1950 & 1951: The first of these projects—Road Test One-MD—was carried out in La Plata, Maryland. Administered by the Highway Research Board and financed by the District of Columbia and 11 states, the study used an existing road to test the impact of round-the-clock truck traffic on concrete pavements: Maryland, Connecticut, Delaware, Illinois, Kentucky, Michigan, New Jersey, Ohio, Pennsylvania, Virginia, and Wisconsin.
1953 & 1954: Following this project, the Western Association of State Highway Officials (WASHO) sponsored a road test in Idaho in 1953 and 1954, suggested by the AASHO Transportation Committee. The WASHO Road Test focused on the impact of heavy truck traffic on flexible (asphalt) pavements. Administered by the Highway Research Board and financed by the highway departments of 11 states’ highway departments:
Idaho, California, Colorado, Nevada, New Mexico, Oregon, Texas, Montana, Utah, Washington, and Wyoming. A 3rd planned road test was abandoned in favor of a more comprehensive research project sponsored by AASHO—was to have been under the aegis of the Mississippi Valley Association of Highway Officials (representing Midwestern states).
Click to go to TRB Circular.
For the reference pages and all information, please see: pp. 81-87 “THE AASHO ROAD TEST” in the TRB compilation of 6 papers: “Pavement Lessons Learned from the AASHO Road Test and Performance of the Interstate Highway System”, click on image above, or go to: http://onlinepubs.trb.org/onlinepubs/circulars/ec118.pdf
For more information on the AASHO Road Test and its legacy, please go to: Federal Highway Administration (FHWA)’s “AASHO Road Test”: https://www.fhwa.dot.gov/infrastructure/50aasho.cfm
For all information, please see the article on the AASHTO website: https://transportationhistory.org/2018/10/15/in-which-we-start-testing-roads/#more-1959
Images above: Figures #10, #11, #12 AASHO Road Test:
(p. 81-87 of TRB: “Pavement Lessons Learned from the AASHO Road Test and Performance of the Interstate Highway System”: Report: “A Historical Look at Interstate Highway System Pavements in the North Central Region” http://onlinepubs.trb.org/onlinepubs/circulars/ec118.pdf).