CELEBRATING THE INTERSTATE’S 50TH ANNIVERSARY THE OF THE INTERSTATE HIGHWAY SYSTEM A 50-Year Retrospective of Advances and Contributions

LESTER A. HOEL AND ANDREW J. SHORT

he Interstate Highway System now mark- bold plan for a limited-access highway system that Hoel is the L.A. Lacy ing its 50th anniversary is the largest and would link the contiguous 48 states. For example, Distinguished Professor most expensive public works project in the geography, geology, and climate of the United of Engineering and U.S. history. The Interstate’s role in pro- States varied greatly from state to state, as did the Director of the Center for Tmoting economic development, strengthening the expertise in highway engineering and construction. Transportation Studies at nation’s defense, and facilitating vehicular travel is the University of well known, but its impact on engineering and tech- Lessons from Rail Virginia, Charlottesville. nology is not widely understood. The experience of the railroad era demonstrated A member of the Although some of the technology and engineering the feasibility of constructing a national transpor- National Academy of expertise needed for this massive undertaking was tation system. Railroad building began on a massive Engineering, he is a past already in place, the 42,500-mile Interstate Highway scale after the Civil War (1861–1865). By 1880, the chair of the TRB System was a complex engineering effort without system included about 94,000 miles of track, which Executive Committee precedent in the history of transportation. Many peaked at more than 254,000 miles in 1918, at the (1986) and of the advances and techniques developed as the project end of World War I. Subcommittee for NRC progressed. Engineers learned important lessons about soil Oversight (1996–2004). behavior, drainage, structural design, and grading Short is a Captain in the On the Shoulders of Giants that would prove useful to the engineers building U.S. Army, completing When President Dwight D. Eisenhower signed the in the 1930s and 1940s. Railroad construction his master of science Federal-Aid Highway Act of 1956 that authorized proceeded without the kinds of equipment and degree in transportation the Interstate project, the concept of a national high- technology that were available for highways in the systems engineering at way system had been under investigation for many 1950s. Many highways followed along the right-of- the University of years. Enormous challenges were associated with the way of previously constructed railroads. Virginia. P HOTO : C ONNECTICUT DOT

Connecticut’s Merritt —shown here near Fairfield—was built in

TR NEWS 244 MAY–JUNE 2006 TR NEWS 244 MAY–JUNE the 1930s and served as a 22 model for the Interstates. TR NEWS 244 MAY–JUNE 2006 23 The Lincoln under The Lincoln Tunnel the Hudson River between City and New New York Jersey was an engineering achievement that provided know-how for the building of the Interstate system. (BPR) and consulting 1 The enabling legislation had anticipated comple- World War II also advanced the state of U.S. War World When hostilities ended in 1945, many returning as well as the U.S. State highway departments, Now the Federal Highway Administration. 1 Overcoming Constraints Overcoming faced the engi- Several unique engineering problems tasked with building the Interstate neers who were con- three around centered system. The problems the scope of the proj- straints: the size of the project, the project. to complete ect, and the time required tion within 13 years, but engineers soon learned that would greatly the scope and cost of the project exceed early estimates of the materials and person- in which In contrast to earlier projects, nel required. the the major challenge was conquering nature, The Golden Gate between San Francisco and Northern California took 4 years to build; The Golden Gate Bridge between San Francisco two towers rise 746 feet. the bridge’s Golden Gate Strait below is 400 feet deep, and construction practice. from Servicemen returning the war had experience with construction equip- ment. In addition, the expanding manufacturing the development of highway con- sector brought struction equipment to a new level of performance. firms, eagerly employed engineering graduates to firms, eagerly employed engineering graduates that would center on the Inter- embark on careers state system. servicemen enrolled in engineering schools funded by in engineering schools funded servicemen enrolled a federal grant known as the GI Bill. Some attended their redirecting state or private universities that were this new area toward programs training and research of studies. Schools such as the University of Califor- and Northwestern University, Yale nia at Berkeley, early leaders in highway engineering University were management education. and traffic of Public Roads Bureau tion projects—including roads, , airstrips, bridges, roads, tion projects—including completed quickly and and harbor facilities—were under adverse conditions. The George Washington Bridge, completed in Bridge, completed Washington The George In 1937, the Golden Gate Bridge connected San Perhaps the best example of an early limited- Perhaps World War II Experience War World II had an impact on the development of War World that would be the highway engineering expertise needed to design and build the Interstate. Military complex challenges in and engineers faced large and Pacific theaters. Many construc- the European 1931, connected New York City with northern New City with northern 1931, connected New York period, its two steel Built over a four-year Jersey. embed- towers with a span length of 3,500 feet are rise The towers and . ded deep in rock suspension steel than 600 feet to support more than 107,000 miles of cables that contain more 300,000 The bridge carries approximately wire. vehicles per day and is one of the most heavily trav- eled bridges in the world. California. Its 4,200-foot span is Francisco to Northern an engineering achievement that continues to serve as for the California highway system. a major artery Bridge and Tunnel Models Bridge and Tunnel and highway bridges and Many railroad 19th and early 20th cen- constructed in the were highways. The Hol- Interstate turies, well before opened in 1927, connected which land Tunnel, It was the lower Manhattan with New Jersey. mechanically venti- world’s first long, underwater, of lated tunnel. The twin-tube design consisted and 130,000 cubic yards 115,000 tons of cast iron the second tunnel Tunnel, The Lincoln of concrete. opened in 1937 and under the Hudson River, for the New York a significant crossing remains Both tunnels served as models area. metropolitan Interstate for those to be constructed during the era for highway and rail transit. access highway is the Pennsylvania Turnpike. Mod- Pennsylvania Turnpike. access highway is the autobahns, the Pennsylvania eled after the German higher geometric opened in 1940 with Turnpike than had been applied in the and design standards United States. The facility still serves as a major and is now a seg- in Pennsylvania east–west artery design ment of the Interstate system. Interstate on similar principles. would be based standards Highway Precedents not America were highways in Limited-access had been freeways in 1956. Parkways and unknown 1920 and 1945. in several states between constructed River Parkways in The Henry Hudson and Bronx and the Merritt Parkway in Connecticut, New York, the Arroyo early are Seco Parkway in Los Angeles that servedexamples of highways for the as models Interstates. 24 TR NEWS 244 MAY–JUNE 2006 Interstates. standards forthe design criteriaand to thedevelopmentof Test, whichcontributed during theAASHORoad truck crossesabridge record dataafteratest Researchers filmand standards forhighways. U.S. geometricanddesign Interstate precursorraised the late1930s.The Pennsylvania Turnpike in Construction onthe and theengineeringstaffs qualified todesignand funds. Onlyafewstates,however, hadtheexpertise of highwaysasaconditionforreceiving federal of 1916required allstatestoestablishadepartment system withintheirstate.TheFederalAidRoadAct were responsible for buildingthesegmentsof percent ofthecost,individualhighwaydepartments Although thefederalgovernmentprovided atleast90 State Preparations excavate materialinlarge cutsectionsandtunnels. used more than1.5milliontonsofexplosivesto lion person-hoursbuildingInterstatehighwaysand infrastructure. Contractorsexpendedabout2.6bil- transportation by earlierbuildersofthenation’s challenges oftheproject greatly exceededthosefaced struction oftheGreat Pyramids.Thecomplexityand the mostextensiveengineeringproject sincethecon- in adifficult andmore hostileenvironment. quently, engineerswere constructingthesefacilities nect citiesandtorelieve traffic congestion.Conse- Interstate systemwasconceivedasameanstocon-

The Interstate Highway System becameknownas The InterstateHighway

: AASHTO : P HOTO American Association of State HighwayOfficials American Associationof Fortuitously, by1956,through theefforts ofBPR,the inPractice Uniformity ment, andcontractorscouldhindercompletion. shortages ofengineers,materials,constructionequip- the desire tosucceedwasstrong, concernsarose that a challengeandanopportunity ofalifetime.Although the Interstatescouldbebuiltonschedule. wouldrespondless hebelievedthattheindustry and “We’re upagainstapretty toughschedule.”Nonethe- to 1961,predicted “manyobstacles”andconceded, work. EllisArmstrong, BPRCommissionerfrom 1958 Interstate program. lish workingrelationships duringthecourseof house staff, contractors,andconsultantswouldestab- employees whowere prepared forthechallenges.In- Pennsylvania hadorganizations withseasoned States suchasNewYork,generation.” California,and neers; thosewhowere hired became“theInterstate construct highwaysatanInterstatescale. way buildingwasanactivepriorityinmanystates. state systemwasbegun,duringaperiodwhenhigh- the firsthalfof20thcentury, longbefore theInter- lishment ofdesignpolicieshadbeenperfected during ments. Theprocess forcommunicationandtheestab- technical informationbetweenstatehighwaydepart- network wasinplaceforcreating andtransmitting developing uniformityandconsistency inengineer- tion ofnewinformationtothehighway community. tator ofhighwayresearch andtoassistindissemina- asafacili- states andthefederalgovernmenttoserve Sciences, establishedrelationships betweenthe emy of Research Councilassociatedwith theNationalAcad- tion, andpromoted highwaydevelopment. to systems, establishedstandards forconstruc- tion betweenstates,brought anorderly arrangement way building,includingtheInterstatesystem. involvementinnationalhigh- federal government’s Great Depression of the1930sandspearheaded the road projects thatwouldemployworkersduringthe Inquiry, helpedstateandlocalgovernmentstocreate 3 2 (AASHO), andtheHighwayResearch Board Transportation Officials. Now theTransportation Research Board. State Highwayand Now theAmericanAssociationof    State highwayengineersrecognized theInterstateas States shared enthusiasmandexcitementforthe Many agenciescompetedtosecure qualifiedengi- These three organizations were instrumentalin HRB, organized in1920aspart oftheNational AASHO, formedin1914,facilitatedcoordina- BPR, establishedin1893astheOffice ofRoad 3 (HRB), a 2 TR NEWS 244 MAY–JUNE 2006 25

SOURCE: IOWA DOT Prototype slip-form developed in the paver, Iowa DOT laboratory in Ames, produced sidewalk-size sections of concrete in 1948, and soon yielded a model that produced sections 9 feet wide and 6 inches deep. In 1876, Belgian chemist Edmund DeSmedt outside of ventured rarely however, Paved roads, Engineers had limited knowledge of the proper- The results became the basis for pavement design became the basis The results supervised the asphalt paving of Pennsylvania and in 1891, George D.C., in Washington, Avenue paved Main Bartholomew in Bellefontaine, Street Ohio, with concrete. Soon other cities in the East and Midwest began paving their roads. cities. When automobiles arrived, the need for hard- to dis- efforts was critical, prompting roads surface cover how to build better pavements. the Interstate, and asphalt before ties of concrete especially about the wearing and load-bearing char- acteristics. Between 1945 and 1955, the total num- ber of automobiles in the nation doubled to 61 million. quality testing of pave- States had conducted knowledge was not devel- ments, but the requisite The Interstates oped until the AASHO Road Test. to be designed for 20 years of service, but many were years, and some portions sections lasted many more to four times the loads for which have carried three designed. they were Advances in Technology Advances in Technology signif- The construction of the Interstates produced par- icant advances in civil engineering technology, pavements, ticularly in asphalt and concrete and traffic drainage, bridge design, soil mechanics, forecasting. practice in the United the States and throughout advanced knowledge world. The AASHO Road Test perfor- of pavement structural design, pavement and the mance, load equivalencies, climatic effects, bridges. design of short-span Army, traveled around the loops continuously for traveled around Army, pavement conditions were than two years. The more pavement design to produce and analyzed measured describing how various pavement relationships to traffic. would deteriorate with exposure structures The testing was conducted in Ottawa, Illinois, vehicles, driven by members of the U.S. Test Highway departments could build Interstate proj- Highway departments In partnership, AASHO and BPR assembled and AASHO and BPR assembled In partnership, and consisted of more than 800 concrete and asphalt than 800 concrete and consisted of more pavement sections arranged in six loops. Each lane with axle loads ranging on the loop carried traffic 2,000 to 30,000 pounds. from AASHO Road Test of the projects One of the most significant research conducted Interstate era was the AASHO Road Test, between 1958 and 1960. The purpose of the project was to develop pavement design criteria for Interstate conditions. pave- for asphalt and concrete Standards a long ments and for bridge design would assure in design life that could withstand expected increases heavy truck travel. ects because of these established standards, which ects because of these established standards, state practice. from secured based on results were lim- Many states had minimal experience in building sensi- creativity, through ited-access highways. Yet and engineering practice, each state could tivity, uniform in some construct highways that were but also unique to the settings. respects, Research Studies Research of the result The policies published by AASHO were based on and experience, engineering research proven studies conducted by BPR, the National Cooperative (NCHRP) established Program Highway Research laboratories, and under HRB in 1962, state research disseminated effectively universities. The partnership design, as geometric information in such subject areas and pavement and bridge design, highway capacity, control. traffic An important feature of the Interstate is the uniformity feature An important opera- safety and efficient in design practice to assure as could be modified, however, tions. Design standards developed. techniques were innovations and new the before codified the knowledge gained by states and communicated the information Interstate project The partnership to all state highway departments. technical knowledge and valuable in sharing proved in establishing consensus within the engineering community. Design and Construction Standards ing practice throughout the country, a necessity for the country, throughout ing practice with the Inter- completion of a system the successful state’sdesign criteria to could tailor scale. Engineers of communication and lines special conditions, the modern dis- as the nation was inventing emerged cipline of highway engineering. 26 TR NEWS 244 MAY–JUNE 2006 8, nearYuma, Arizona. Telegraph Pass,Interstate admixtures. High-performance concrete wasintro- include fiberreinforcement andsuperplasticizersfor ing constructionworkers’productivity. more efficient paverswere developed,greatly increas- With theconstructionofInterstate,larger and produced asection9feetwideand6inchesdeep. Two yearslater, aslip-formpaverwasavailablethat form paver, in1947. developedinanIowalaboratory than on-siteproduction. The centralplantmixerwasupto12timesfaster the concrete placementandthequalityofmix. directly to theproject site,improving thespeedof tral mixer, concrete truckscouldtakethemix duced on-site.With thedevelopmentofalarge cen- until 1960,theconcrete forpavementswaspro- each wasuniquetothebuilder. From the1920s costs. Thefirstconcrete roads were primitive,and asphalt butlastslongerandhaslowermaintenance Concrete generallyhasahigherinitialcostthan Concrete tion, makingitlessprone tocracking. and odor;wouldagemore slowlyinproduc- produce themix;wouldreduce emissions,fumes, This newtechnologywouldrequire lessenergy to for asphaltpavementmaterialby50to100degrees. lower theproduction andconstructiontemperature the developmentofwarm-mixasphalt,whichmay economical pavingmaterialcontinues.Underwayis water, reducing hydroplaning andskidding. course designhasimproved surface drainageof highway performance. Theopen-gradedfriction climate andtraffic andhasshowndurabilityin Performing AsphaltPavement—canbetailored to Superior Superpave—which standsfor courses. stone-matrix asphalt,andopen-gradedfriction Superpave®, asphalt pavementdesigninclude in thepast50years.Recentimprovements in remain thesame,butmanyelementshavechanged foundation forasphaltsurfacing. ods, whichenabledtheuseofwornroadbeds asthe art includedrubblizationandcrack-and-seatmeth- tion techniquesthatnoware considered stateofthe wheel rollers were developed.Innovativeconstruc- steel- for pavingtwolanesatonce,andvibratory able. Electronic levelingcontrols, extrawidefinishers struction calledforlarger equipmentthanwasavail- could withstandheavyloads.ButInterstatecon- War aircraft IIbecausemilitary required surfaces that Asphalt technologygreatly improved duringWorld Asphalt Other improvements inconcrete technology Another advanceinconcrete pavingwastheslip- Research toproduce aquieter, more durable,and The basicprinciplesofhighwayconstruction and LosAngeles. Thepioneereffort wasthe1955 had beeninitiatedincitiessuch asChicago,Detroit, in itsinfancy. design, thestateofart intravelforecasting was future. Incontrasttootheraspectsof engineering accommodate traffic volumes20 yearsintothe ning becausethedesignhadtosizesystem Travel forecasting forInterstateplan- wasnecessary Planning tion, andbridgemanagementsystems. epoxy-coated reinforcement, radiographicinspec- design, cable-stayedspans,elastomericbearings, welded connections,computerizedanalysisand concrete, high-strength steel,weathering concrete, segmental construction,high-performance highway bridgesduringthepast50years:prestressed list ofadvancesthatcameintowidespread useon during theInterstateyearsisillustratedbyapartial Bridge openedin1883. before theInterstate.Forexample,Brooklyn for railroads andhighwayshadbeenconstructed As notedearlier, manylong-andshort-span bridges Bridges ber ofjoints,savinglaborandinstallationtime. longlengthreduced thenum- Olympics. Thepipe’s billion project onI-15intimeforthe2002Winter gated polyethylenepipeallowedcompletionofa$1.5 Salt LakeCity,project in Utah,forexample, corru- vided engineerswithanotheralternative.Inarecent or concrete culverts. and duringthe1950s,highwaybuildersusedmetal Interstate, culverts were madeofclayorconcrete, including culvert designandmaterials.Before the The Interstatealsoadvanceddrainagetechniques, andDrainage Culverts ity concrete fordurabilityandlongevity. later fullyunderstoodtheimplicationsofhigh-qual- for speedyconstruction.Engineersandcontractors the Interstate,qualitycontrol oftenwassacrificed was availableinsmallquantitiesattheinceptionof cal andlong-lasting.Althoughhigh-qualityconcrete reconstructing oldpavements. developing more economicalwaysofrecycling and loads, findingsolutionstodurabilityproblems, and performance ofalternativedesignsunderdynamic into pavementmanagementsystems,comparingthe pavements includeimproving informationforinputs duced in1987.Areas ofongoingresearch onconcrete Large-scale urbantransportation planningstudies Yet thedramatic progress inbridgeengineering Today thedevelopmentofplasticpipeshaspro- The goalistodevisemixtures thatare economi- TR NEWS 244 MAY–JUNE 2006 29

SOURCE: MASSACHUSETTS TRANSIT AUTHORITY Boston’s 14-year Central Boston’s Project, Artery–Tunnel known as the Big Dig, has reconfigured the juncture of I-90 and I-93. As Stephen D. Bechtel, Jr., a noted engineer and As Stephen D. Bechtel, Jr., As the 21st century begins, the engineers and The most recent engineering challenge was the I- engineering The most recent Engineers employed the slurry to wall technique highway builder, has stated: “For those of us who are highway builder, to have been trained and to serve as engi- fortunate his- satisfaction in working on is great neers, there They projects. infrastructure toric and important the quality of life, in both safety and con- improve and eco- commerce venience, and facilitate improved the world.” around nomic growth planners who designed and built the Interstate High- way It is of their careers. in the twilight System are the lessons learned and skills to remember important in completing the Interstate Highway acquired Sys- has passed to a new generation of tem. The torch engineers who will face new chal- transportation lenges in a fast and changing technological world. Looking Ahead challenges in Engineers will continue to address and adapting the Interstate maintaining, improving, Highway and to the System to the needs of the future information age. The can-do attitude of the Interstate for transportation the standard generation remains engineers today and in the future. length and that feature two mile-long tunnels two mile-long length and that feature of com- beneath the ocean bottom to allow passage and military ships. mercial or Big Project, 90 and I-93 Central Artery–Tunnel elevated Dig, in Boston, Massachusetts. The original congested, plagued by highway was chronically ramps. sharp turns and many entrance and exit walls on which the 120-foot deep concrete create was con- while a new road old highway could rest walls also stabilized The concrete structed below. cave-ins during the construction site and prevented and five the tunneling. Completed over budget project years behind schedule, the $15 billion engi- an outstanding nonetheless is considered neering accomplishment. The Chesapeake Bay Bridge–Tunnel in Norfolk, The Chesapeake Bay Bridge–Tunnel Road safety standards also have improved in the have improved also Road safety standards Other contributors were Alan Voorhees, whose Alan Voorhees, were Other contributors Virginia, opened in 1964 and was named one of the Virginia, of the Modern World” “Seven Engineering Wonders connects Vir- in a 1965 competition. The structure Eastern to Virginia’s ginia Beach and Norfolk Shore, with bridges and tunnels that total 17.6 miles in Other Advances with it many advances that The Interstate has brought but to many have contributed not only to the highway, Engineers have adapted other engineering projects. laws highway design to comply with environmental For example, in Florida’sand regulations. Everglades, the construction of I-75—known as Alligator Alley— included underpasses that allow the endangered under the Florida panther and other wildlife to cross drainage also has enhanced the Improved highway. flow of water within the Everglades. past 50 years. As early as 1960, researchers were past 50 years. As early as 1960, researchers for highway pave- markings developing reflective guardrail ments. Other developments include signs, breakaway designs such as the Jersey Barrier, signs. Con- traffic clear zones, and reflectorized for highway safety struction zone practices assure workers. Statistics show that the Interstates have had of all classes of roadways. the best safety record Operations and Safety monitoring was another challenge for high- Travel in this way engineers. Among the many advances the 27-kilometer roadway, is the first high-tech area I-105 in Los Glenn Anderson Freeway–Transitway, opened in Angeles. This Interstate section, which with the latest in highway technology, 1993, features to com- sensors buried in the pavement and links flow. traffic puters that allow technicians to monitor on traffic In addition to meters that help regulate offi- television cameras alert ramps, closed-circuit cials to accidents on the highway. seminal paper, “A General Theory of Traffic Move- “A General Theory of Traffic seminal paper, a “gravity model” for forecasting ment,” proposed His planning firm and trip origins and destinations. studies apply- transportation others completed many the planning BPR perfected ing these principles. for the Interstate, which have methods developed in many urban transportation been implemented studies in the United States and worldwide. Chicago Area Transportation Study, which developed Study, Transportation Chicago Area flow patterns and traffic to forecast a series of models that procedure methodological four-step based on a distribution, modal generation, trip included trip these models assignment. Many of split, and traffic still in use today. are