Madanat, Samer

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UC BerkeleyACCESS MagazineTitleThe Road Ahead: Managing PavementsPermalinkhttps://escholarship.org/uc/item/2vp7q3mxJournalACCESS Magazine, 1(17)AuthorMadanat, SamerPublication Date2000-10-01Copyright InformationThis work is made available under the terms of a Creative Commons Attribution-NonCommercial License, availalbe at https://creativecommons.org/licenses/by-nc/3.0/ Peer reviewedeScholarship.org Powered by the California Digital LibraryUniversity of California26A  C  C  E  S  SAN E W-L A I D S T R E T C H O F PAV E M E N T is not a finished p roduct. Tr a f fic pounds it; hot sun heats and expandsit; water gets inside and washes away the soil beneathit. Depending on these forces and the quality of its design andc o n s t ruction, a pavement will last only a limited time before itneeds repair or replacement. Because there are so many factorsinvolved, it’s not possible to just schedule a replacement in x number of years. The pavement has to be checked periodicallyfor potholes and cracks and ruts. Visual and manual inspectionscan be slow, hazardous, and fraught with uncert a i n t y. But that’sthe way it’s always been done.N o w, however, there is a whole range of new technologies available that can quickly, accurately, and safely check the c u rrent condition of a pavement. Although the tools and tech-niques are not cheap, they can potentially save a lot of money byp e rmitting accurate diagnosis and rational management, thuseliminating unnecessary repairs. But the technology itself is not enough. Agencies in charge of maintaining pavements needfirst to accept these technological developments and then theo rganizational changes they imply. S a m e r  M a d a n a t  i s  a s s o c i a t e  p r o f e s s o r  o f  C i v i l  a n d  E n v i r o n m e n t a l  E n g i n e e r i n g  a t  t h eU n i v e r s i t y  o f  C a l i f o r n i a ,  B e r k e l e y  ( m a d a n a t @ c e . b e r k e l e y. e d u )TH E RO A D AH E A D:Managing Pavements B Y  S A M E R  M A D A N A T27 A  C  C  E  S  SN U M B E R  1 7 ,  F A L L  2 0 0 0CURRENT PAVEMENT MANAGEMENTHighway agencies developed what they call pavement management systems to p rovide systematic pavement maintenance and re p a i r. Regular inspections re c o rd cur-rent conditions such as cracking, rutting, roughness, and skid resistance. A common wayto use this information is to consolidate it into a single number, such as the PavementCondition Index. Managers then correlate the PCI with the pavement’s age and pre d i c twhen the PCI will fall below a standardized level. Then, plans can be made for futuremaintenance, re p a i r, or re c o n s t ruction of the pavement. But there ’s lots of room for uncertainty in these methods. Surface conditions onlyhint at a pro b l e m ’s underlying causes. Although an experienced engineer can make a very good guess about what makes a road crack in a particular way, it’s still a guess.The information that goes into the index is subject to errors, from sources as diverse astechnological limitations of inspection equipment, imprecise data, and human error inp rocessing. The perf o rm a n c e - p rediction models themselves create some uncert a i n t y.These possible errors compound, increasing the likelihood of a wrong maintenance deci-sion. Prediction models try to account for these uncertainties by creating a broad rangeof decision possibilities, but basically it’s difficult to choose precisely the right re p a i r. And any time a wrong choice is made, costs go up. NEW INSPECTION TECHNOLOGIESDuring the past ten to fifteen years there has been rapid introduction of automatedhigh-speed pavement-condition inspection technologies. Commercial systems now avail-able can continuously measure and re c o rd the type, degree, and intensity of cracking;the width, depth, and pro file of rutting; and the thickness of the pavement layer, all at n o rmal driving speed. These high-speed surveying systems can provide in-depth pave-ment inspection with a level of detail and accuracy never before attainable. ➢High-speedsurveyingsystems can provide in-depthpavementinspection with a level of detail andaccuracynever beforeattainable.28A  C  C  E  S  SBecause they can collect information at driving speed, they dispense with the needto block lanes, disrupt traffic, and endanger workers. They also are not subject to thesame limitations as older methods, as for example when estimating cracking, conven-tionally a slow process involving visual observation and manual measurement. Video andlaser crack detectors now identify and measure cracks quickly and accurately. Gro u n d -penetrating radar provides invaluable and here t o f o re unattainable information aboutpavement layer thickness. And rutting can be spotted and accurately measured with optical, laser, or ultrasonic sensors.The re v o l u t i o n a ry aspect of these new technologies, the thing that could change theway pavements are re p a i red and maintained, is the simultaneous collection of all theseseparate bits of information over a single stretch of pavement. No longer is it necessaryto correlate piecemeal evaluations of separate factors and then guess at underlyingcauses. These new methods can create a complex picture of a pavement’s condition, evaluating multiple factors over a specific distance.THE INST ITUTIONAL CHALLENGEC u rrent pavement management systems work well enough, given the real limita-tions of equipment. Even the PCI is an acceptable, if cumbersome, way to use complexand uncertain information. But the advent of new technologies offers an opportunity anda challenge to highway agencies to do better. M e rely obtaining equipment and training is not enough to assure cost savings fro mthese new methods. Instead, the pavement management system itself needs to be re f o rmulated. I recommend four institutional changes to exploit all this newly availablei n f o rmation and promote better maintenance decisions.First, stop compiling and summarizing the information into a single index. Clearly,all the information pouring out of these new machines will go to waste if managers continue to reduce the information to one generic number. Instead, develop a 3-D imagethat connects the various kinds of information and gives a more complete picture of pavement condition. Second, because we can see a deeper and more complex picture of the pavement,we can develop new computer-based predictions that eliminate much of the uncert a i n t ymanagers must now account for in their plans. For example, cracking is caused either byfatigue or by rapidly changing temperatures. Fatigue is a result of strain in the pavements t ru c t u re, which in turn is a result of load (vehicle number and weight), layer thickness,and layer stiffness. On the other hand, thermal cracking is caused by thermal stre s s e sresulting from daily temperature variations. Since load, temperature, and cracking cannow be continuously and accurately measured, there is enough information to determ i n ethe exact cause of cracking. As a result of better understanding the causes, we can alsop redict the future rate of cracking and thus allow managers to make more exact mainte-nance decisions.T h i rd, change the process of making maintenance decisions. With less uncert a i n t y,the need for caution in planning is lessened, so managers will be less inclined to over-compensate by ordering repairs that are pre m a t u re and too extensive. For example, ifmanagers have more confidence in their ability to predict pavement life, they can re d u c ethe amounts of funds that are often set aside for emergency repair work. Although anexperiencedengineer canmake a verygood guessabout whatmakes a roadcrack in aparticular way,it’s still a guess.29 A  C  C  E  S  SN U M B E R  1 7 ,  F A L L  2 0 0 0F o u rth, and perhaps most useful, develop adaptive models that can learn over time,c reating an institutional memory. That is, instead of relying solely on the practiced eyeof a human inspector who, through experience, has learned the likely causes of pavementp roblems, create a self-learning system. Adapting to feedback from real conditions asthey change, such a system can adjust its predictions accord i n g l y. Thus more and moreaccurate predictions based on complex information will become available over time.THE REAL FIXAs they must in virtually every field, technological developments compel the agencies that adopt them to also adapt to them. New ways of attacking problems call fornew styles of management and hence new modes of organization. As pavement manage-ment shifts from visual and manual inspection to automated monitoring, the roles ofinspectors will necessarily shift as well. With demands for diff e rent skills than were f o rmerly sufficient, there will inevitably be demands for new staff equipped to superv i s eand apply the new electronics and optics. In turn there will be demands for revised methods of decision making and changed channels of authority.These necessary changes will not happen simply because they should. There is av e ry serious need for the re s e a rch community to assist state and federal transport a t i o nagencies to improve their data-collection schemes, perf o rm a n c e - p rediction models, anddecision-making pro c e d u res. In the 1980s, substantial re s e a rch eff o rt was dire c t e dt o w a rds developing the first generation of pavement and bridge management systems. A similar endeavor is needed now to modernize these systems, so that they can make themost of new technologies.It will no doubt take a while before the new pavement-management techniques canbe fully adopted, because responsible agencies will need time to adapt themselves to thenew tools and techniques. There can be no question that they will—preferably soonerthan later of course. And, once the institutions do adapt, the potholes and cracks will getfixed sooner, the maintenance budgets will be smaller, and the ride will be smoother. ◆F U R T H E R  R E A D I N GSamer Madanat, “Incorporating InspectionDecisions in Pavement Management Systems,”Transportation Research, v. 27B, no. 6, PergamonPress, 1993.Samer Madanat and Moshe Ben-Akiva, “OptimalInspection and Repair Policies for TransportationFacilities,” Transportation Science, v. 28, no. 1,1994.Ken Maser, Brian Bradmeyer, and RichardLittlefield, “Pavement Condition Diagnosis Basedon Multisensor Data,” Transportation ResearchRecord 11, 96 (Transportation Research Board,Washington DC, 1989).Mohammad Shahin and Steve Kohn, “PavementMaintenance Management for Roads and ParkingLots,” Technical Report M-294 (ConstructionEngineering Research Laboratory, US Army Corpsof Engineers, Urbana-Champaign, IL, 1981).Kelvin Wang, “Designs and Implementations ofAutomated Systems for Pavement SurfaceDistress Survey,” ASCE Journal of InfrastructureSystems, v. 6, no. 1, 2000.

The Road Ahead: Managing Pavements

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