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APPENDIX E DESC~PlION OF S~OOTHNES~EASORINC EgOIP~ENT

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APPENDIX E. DESCRIPTION OF SMOOTHNESS-MEASURING EQUIPMENT Introduction Over the last century, a vast array of equipment has been developed to evaluate the smoothness of pavements. The first of these devices was developed on early paving projects, while some have been developed In connection with the construction of test roads. Many of these employed some innovative approaches in the attempt to quantify and ensure pavement smoothness, and even the early models tended to be quite sophisticated. In recent years, the growing interest in pavement management systems has focused on pavement ride as the major factor In evaluating the serviceability of a road, Hereby creating the need for economically evaluating the extensive mileage of a highway system. Electronics and space age-technology have been applied, creating an ever-changing approach to the subject. This appendix describes the significant types of equipment that have been used for evaluating the smoothness of pavement surfaces. Those devices that are currently being used by major highway agencies, as well as those that are believed to provide a potential contribution in the immediate future, are covered in depth. Smoothness Measuring Equipment Used in Construction Currently, there are a variety of types of equipment in use for measuring the smoothness of newly constructed pavements. Table E-l shows the breakdown of usage among the 47 States and 3 federal agencies that responded to the agency questionnaire. Discussed in this appendix are the pavement smoothness measuring systems currently used for crucial construction smoothness quality control testing and listed In table E-~. Several other profile- and smoo~ness-measur~ng systems have been used for pavement management purposes, including numerous high-speed profile measuring systems. Certainly, some of these systems also have application in initial pavement smoothness measurement. New smoothness measurement equipment is being developed, and these systems are also described in the following sections. Straightedge / Stringline Perhaps the most basic method of locating surface longitudinal and transverse pavement irregularities is win me use of a straightedge or stringline. Straightedge devices are usually made of wood or metal and can be of any convenient length, typically in the range of ~ to 16 It (2.4 to 4.9 m). A wire or string stretched tightly from the ends of a bow-shaped form is also sometimes used. When the straightedge E-!

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Table Eel. Agency use of smoothness-measur~ng equipment. 1 Equipment Type | No. of Agencies Using l l Californ~a-type Profilograph (generic) | 33 l Rainhart Profilograph 7 Mays Meter (Vehicle mounted) | 2 Mays Meter (Trailer mounted) | 5 l | GM Type Profilometer | 4 Rolling Straight Edge 1 | Straight Edge or String line | 33a l l a six agencies use this category as Me sole method of smoothness measurement, and me remaining use it to augment over smoothness testing. Or stringline is placed on the pavement surface, variations in the pavement surface from the straightedge can be readily seen and measured. Smoothness is controlled by allowing no more than a specified deviation from the straightedge when placed on the pavement surface. Use of this approach is very labor intensive, because We person doing the measuring must be very close to the pavement surface, generally in a kneeling position, to determine if any deviation exists. Continuous longitudinal pavement surface coverage using straightedges is usually not practical, but Me evaluation of localized areas can be addressed adequately. Application is limited to identification Of short wavelength roughness, since measurement accuracy diminishes for pavement surface wavelengths greater Man about one-half the straightedge length. Since Me straightedge looks at a pavement surface from a "snapshot" viewpoint, its output can vary greatly from that determined using a profilograph. For example, a New York DOT study in 1960 found that straightedge results from measured ramps noted 25 percent more displacement than a profilograph. However, on mainline highways the straightedge results contained 50 percent less displacement (Scofield 1993~. This is assumed to be a result of Me tremendous effort required to measure mainline pavement surfaces and the associated fatigue effects. Although use of more sophisticated smoothness measuring equipment is the norm for use on most mainline paving projects, there are some situations in which the straightedge may be the primary method of measuring smoothness. About two- ~irds of the State agencies polled in 1994 indicate that straightedges are used to augment other forms of smoothness control. E-2

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Rolling Straightedge Rolling straightedge equipment, as shown in figure E-1, consists of a rigid straightedge beam with wheels at each end. At the beam midpoint is a third wheel, riding on the pavement surface, which is linked to an Indicator showing the deviation from the straightedge plane. One United States manufacturer, ELK International-Soiltest supplies a generic rolling straightedge under the name Hi-Low Detector. It is a precision-made rectangular aluminum beam from 10 to 16 It (3.0 to 4.9 m) long with riding wheels at the ends and a detector wheel at the middle. The system is pushed lengthwise at walking speed by hand from the rear where the operator can steer the detector and control the spray marking system. If the deviation from the straightedge plane is greater than is allowable, the operator can trigger an inverted spray canister from the steering handle to mark the location of high or low pavement surface deviations. Calibration can be done by hand on a level surface. The rolling straightedge is slow and incapable of measuring "true" pavement surface profile. No record of the equipment output is provided by this system except for the paint markings on the pavements surface, but it is useful for bridge decks and small projects. Costs for the 10- to 16-ft (3.0- to 4.9-m) systems in 1995 range from $3,300 to $4,300. Figure E-~. Rolling straightedge. (Source: ELK) E-3

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Profilograph Equipment The term profilograph refers to a rigid frame device carried by a system of support wheels that provides a dawn from which pavement surface deviation measurements can be made. A profile wheel, which rests on the pavement surface at the center of the unit, is linked to a mechanical strip chart recorder or computer, and variations In vertical movement of the profile wheel with respect to the established datum are recorded. For the mecharucal models, Me strip chart is then evaluated manually or electronically. Computerized models are programmed to produce a strip chart and a tabulation of pertinent smoothness information automatically. All of the devices in this category are operated In the range of 2 to 3 mi/hr (3.2 to 4.S km/hr). Two basic types of profiIograph have evolved, differing In We support wheel configuration. Support wheels on Me California-type profilograph have varied in number from four to twelve, with systems in many States using twelve wheels. These wheels are attached to the ends of a 25 It (7.6 m) truss and mounted on a mulliple-axie carriage Cat includes four wheels 17 in (432 mm) from Me truss centerline and two wheels 17 In (432 mm) on the opposite side of the truss centerline. The support wheels are commonly spaced at 2.7 it (0.82 m) intervals and positioned near the ends of the tmss, resulting In an overall profilograph span of about 33 It (10.0 m). The twelve support wheels for Me Rainhart-type profilograph are evenly spaced along its 24.75 it (7.5 m) span at offsets up to 22 in (559 mm) such that no wheel follows the same path. On bow systems, the front support wheels can be steered by the operator. The following sections will provide a short history of the profilograph systems and discuss several of the different models within the profilograph group. These include the Cox, McCracken, Ames, SSI, Paveset, Soiltest, and Rainhart systems. California ProfiIograph Background The development of the California profilograph followed many avenues in Me period from the 1930s to Me 1950s. Units win a beam length ranging from 10 ft to 30 ft (3.] m to 9.3 m) were used and the model that ultimately became popular has a length of 25 It (7.6 m). This type has come to be known generically as Me California profilograph, developed under Me direction of F. N. Hveem, former Materials and Research Engineer with Me California Division of Highways, and is described In a classic report from Mat era (Hveem 1960~. The basic 25-ft (7.~m) long California profilograph, as developed In the late 1950s, is typically supported be a carriage of six wheels at each end, arranged In an articulated manner and provided win steering capability. (Current models in use by the State of California consist of a single axle and two wheels at each end of the 25 It [7.6 m] beam.) A profile wheel is located at Me beam midpoint and is linked to a recorder Mat provides a paper strip chart showing changes in Me distance between the pavement at Me point of the profile wheel and the datum established by the E-4

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carrying wheels. The strip chart produces the deviations on a true vertical scale and on a 1:300 (25 ft/in [0.3 m/mm]) horizontal scale. Overall pavement smoothness is expressed by this equipment in terms of its "profile index" (Pl) and a tolerance for individual bumps. Pi is expressed in inches per mile (mm per km) and represents the total accumulated excursion of the strip chart trace beyond a tolerance zone. That tolerance zone typically ranges from 0.2 in (0.5 mm) to less than 0.001 in (0.025 ~run). For individual bumps the tolerance limit is expressed as some height, usually 0.3 in (7.6 mm) over a 25 ft (7.6 m) base length as read on Me strip chart. Some agencies use 0.4 in (10.2 mm) or 0.5 in (12.7 mm) tolerance levels. When the specifications are exceeded, it is necessary to identify the individual bumps on the pavement surface so that grinding can be completed to remove the bumps. Methods for analysis if the strip chart profiIogram include manual and computerized techniques. Manual evaluation of the strip chart is done using two clear plastic templates. The profile index is determined for each 0.! mi (0.16 km) of pavement using a plastic template 21.12 In (536.45 mm) long (21.12 in x 25 ft/in = 528 It [161 mid. The template is scribed in 0.1 in (2.5 mm) vertical increments to allow the vertical excursion to be counted. A smoothness tolerance represented by a blanking band runs the length of Me template. The blanking band is typically 0.2-in ,_ ~ ~ .. . . ~ ~ ~ ~ . `~ _ ~ . ~ ~ ~ ~ to.l-mm) wine; however, some agencies nave used a U.1-ln t;~.~-mm) wine nancl and some have used a 0.0-in blanking band. The blanking band, when used, is placed on the profile to cover as much of Me trace as possible. The accumulated distances of the trace above and below Me blanking band are used to determine the profile index. Individual bumps are manually identified using a second clear plastic template with a ~ in (25 mm) scribed base length and a parallel I-in (25-mm) long slot separated by Me bump tolerance limit, typically 0.3 in (7.6 mm). Computerized recording and analysis of profiIogram traces is completed by the manufacturer's software, once the appropriate parameters have been defined. Prior to completing the measurement pass, the critical bump height and blanking band width defined by the applicable specification must be defined. In addition, the computer filter setting, which essentially defines the baseline trace, is selected. The Cox and McCracken manufacturers have developed data filters in an effort to match the electronic data profiIogram to Me trace Mat would be measured by a manual profiIograph. Cox produces a baseline trace and accompanying null band by filtering a copy of the profiIogram to remove short-wavelength chaNer and produce a smooth trace that matches the profile trend. The McCracken profiIograph software reportedly breaks Me section into shorter intervals and analyzes the short intervals by the standard manual methodology (Scofield 1993~. The 25-ft (7.6-m) long frame for the profiIograph is comprised of five segments for ease of transportation and storage. All of the frame segments and the wheel assemblies, steering mechanism, and recorder can be carried in a pickup or van and assembled at the job site. Propulsion can be manual or by the use of a small E-5

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motorized unit that is attached alongside the profilograph. carries the operator as well as propelling the equipment. The propulsion unit California implemented a profiIograph specification for concrete pavements . beginning In IV58 All of the California ~01~ prohlographs have been constructed ~ the machine shop of the Materials and Research Department, and the fleet eventually grew to about 20 units. They were built with various materials over the years. Early frames were constructed using plywood boxes, and later devices were built with rectangular aluminum tubing. Different recorder designs have been used and the wheel assembly was redesigned in 1983 to consist of a total of four wheels rather than We twelve Cat were used: earlier. As other agencies adopted the California profiIograph, obtaining the device was somewhat difficult. Some States constructed them in Weir own shops or In a local machine shop using plans obtained from CALTRANS. As Me demand grew, Me units were made available commercially. At the present time, Me California profilograph is being marketed by five firms: Cox and Sons, McCracken Division of International Pipe Machinery Corp, Ames Corporation, ELK International-Soillest, and Surface Systems and Instruments-~LC. A dual-lane testing system was also recently Introduced by Paveset America. The accuracy, repeatability, and ease of use reportedly varies between these systems. Numerous State Agencies have developed detailed descriptions for operating profilographs and for evaluating the profilogram traces. The American Society for Testing and Materials has developed a standard method for profilograph testing- ASTM E 1274, "Standard Test Method for Measuring Pavement Roughness Using a Profilograph." In 1978, Me California DOT prepared their latest revision of California Test 526 "Operation of the California Profilograph and Evaluation of Profiles." The increased use of Me California-type profilograph over Me past 35 years suggests that it has filled a definite need in the area of construction smoothness control. However, there is growing concern about certain lunitations of this instrument, including the following (Scofield 1992; Scofield, Kalevela and Anderson 1992): Speed The slow operating speed of 2 to 3 mi/hr (3.2 to 4.8 km/hr) is becoming less tolerable. Agencies need a faster way to obtain profile v information. Precision- Recent studies have focused on the precision of Me instrument and trace evaluation methods operating under Me current state of the art. It is questionable whether the profile index can be obtained win adequate precision to justify its use in specifications that have incentive/dis~ncentive payments based on ~ in/ml (0.02 m/k~rl) increments. For example, a 1992 study by the Arizona DOT found that Me average standard deviation was 1.9 n/mi for four trace reduction operators on new pavements win average PI ratings from 2.6 to 4.S ~n/mi (Scofield 1992~. On four rougher sections, with an average PI of 8.6 ~n/mi (136 mm/km), Me average standard deviation was E-6

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. . 1.6 in/ml (25.3 mm/km). For mechanical and computerized profilographs, the range of test results for the same pavement with the same operator and trace reducer was between 3.5 and 7.0 in/ml (55.3 and 110.6 mm/km) for a smooth section and between 7.0 and 11.0 (~10.6 and 173.S mm/km) for a rougher wheelpa~. This is clearly more variability than can be considered acceptable for Implementing ~ncentive/disincentive specifications. The combination of variability from trace reduction, test path location, equipment properties, and computer filter settings makes obtaining precise smoothness statistics with the profilograph difficult. Smoothness Index With the growing Interest in pavement management systems and the Increased sophistication that is being applied to this activity, there is interest in moving away from Me profile index standard and adopting some other sublunary statistic such as the International Roughness Index (IRI) or Root Mean Square Vertical Acceleration (RMSVA), neither of which can be obtained using a profiIograph. This would allow a given index to be used for new construction and throughout the life of the pavement. Relation to User Response Because Me profilogram is known to amplify and attenuate Me true pavement surface profile, there is some concern about how well the profilograph output relates to the wavelengths of a pavement profile that are felt by highway users. Several cases have been documented in which new pavements that received low PI ratings, and in some cases incentive payments, were found by the roadway users to be uncomfortably rough. This calls into question the suitability of using profilograph data for construction control and suggests the need for refinement in evaluation procedures (Parcells 1992; Scofield 1992~. California ProfiIograph-Cox Models James Cox and Sons, Inc. of Colfax, California, began manufacturing profilographs in 1973. The basic parameters of the California type were adhered to, but Cox developed numerous innovations in design and construction. In the mid-19SOs, Cox developed a computerized version, shown in figure E-2, that is currently marketed as Model CS 8200 at a 1995 price of approximately $24,000. The CS 8200 is a microcomputer-based profile measuring device designed to measure roadway profiles and to reduce profile data in accordance with test method Califorrua 526 (1978~. The CS 8200 reduces Me measured profile data and generates graphic reports containing the measured profile annotated win stationing, excursion information, and documentation points. Profilograms may be reduced to obtain profile index or high points or may do bow sunultaneously. Cox no longer markets a manual profilograph. California ProfiIograph-McCracken The McCracken Division of International Pipe Machinery Corp. of Sioux City, Iowa, has marketed mechanical profilographs since 1984 and a computerized mode] since 1990. They are priced (1995) at approximately $16,000 and $26,000, respectively. E-7

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Figure E-2. James Cox & Sons, Inc. computerized profilograph. (Source: Cox & Sons) The computerized version, illustrated in figure E-3, is fully capable of automatically providing Me full analysis of profile information in a manner similar to that performed by the Cox machine. The manufacturer indicates that PI repeatability with one unit and one operator is about 7 percent (0.5 in/ml [7.9 mm/km] for 7 in/ml [~10.6 mm/km] pavement). California ProfiIograph Ames The Ames Unit is manufactured by Ames ProfiIograph of Ames, Iowa was developed In 1986. Bow a manual and a computerized version are available, priced at approximately $10,000 and $22,000, respectively (1995~. The manual unit is referred to simply as the Ames ProfiIograph and the computerized unit is known as Computerized ProfiIograph Mode! 4000. The Ames units are designed to produce the same profile trace as the other California type units that have been mentioned, but it is considerably different In basic design, as shown in figure E-4. The wheel assemblies are similar to those of over models in that an articulated system consisting of a total of six wheels is used to support each enct of the device. E-8

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Figure E-3. IPMC McCracken computerized profilograph. (Source: IPMC) .~.... Figure E-4. Ames computerized profilograph. (Source: Ames Profilograph) E-9

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ICC MDR Profiling System The South Dakota profiling system is now manufactured commercially by International Cybernetics Corporation (ICC) of Clearwater, Florida. This company has a family of road profiler equipment in its "Mobile Data Recorder" (MDR) product line, each mounted in a small- to mid-sized cargo van. These include the following: MDR 4084 Profile/Roughness System featuring Profile/IR] in one wheelpath; average rut depth in two wheelpaths to center of lane; one inertial reference accelerometer; three height sensors; one linear distance sensor, and a m~rumum recording interval of 3 in (76 mm). MDR 4085 Enhanced Profile/Rut depth/Roughness System featuring profile/IRI in two wheelpaths; average or half-car simulation {RI; average rut depth in two wheelpaths to center of lane; two inertial reference accelerometers; three height sensors; one linear distance sensor, and a 3 in (76 mm) minimum recording interval. MDR 4087 Enhanced Profile/Rut depth/Roughness System, shown in figure E- 9, featuring profile/IRI in two wheelpaths; average or half-car simulation IRI; average rut depth In each wheelpath; two inertial reference accelerometers; five or more height sensors one linear distance sensor, and a minimum recording interval of 3 in (76 mm). ~ _ _ ~ __ Figure E-9. ICC MDR 4087 profiler. (Source: ICC)

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International Cybernetics Corporation offers ultrasonic or laser sensors on all current MAR systems. The lasers are more expensive than the ultrasonic sensors but offer several advantages. First, the lasers can be used when roads are wet as long as there is no standing water to alter the readings. Second, more data points can be sampled with the laser so that a better average height can be obtained, allowing better repeatability. Also, the laser is less sensitive to temperature changes, which may occur quickly in hilly or changing terrain. Finally, the accuracy of ultrasonic sensors is affected by macrotexture on asphalt pavements, according to a national study (Perera 1994~. Reported accuracy of the distance measuring system is 0.02 percent. The standard deviation of two laser-based {CC MDR 4087-L systems tested in 1993 on eight sections at four sites was 4 for AC pavements and 2 for PCC pavements. IRI at the sites ranged from 55 in/ml (869 mm/km) to more than 300 in/ml (4,740 mm/km) (Perera 1994~. Setup effort, including equipment warm up, calibration, and system initialization, for this type of system is minimal, requiring 15 to 30 minutes. Data can be collected at highway speeds, and is stored and processed by computer. Costs of these systems range from $80,000 to $110,000 in 1995 dollars. A single wheelpath portable laser profiler is also available for $45,000. Dynatest Profiling System In 1995, Dynatest introduced a fully-automated roughness measurement test system called the Model 5051 RSP (Road Surface Profiler) to meet the FHWA Long Term Pavement Performance monitoring specifications. The base system, mounted on Me front of a mid-s~zed van, generates response-type output using a single accelerometer. The system is shown in figure E-IO. Up to eleven lasers can be added to the response-type system, using the in-place accelerometer, to provide longitudinal and transverse pavement surface profile and rutting information ~ real tune at speeds up to 100 km/hr (62 mi/hr). The lasers and accelerometers can be mounted in single boxes, S.5-ft (2.~m) rut bars, and In fold-out extensions to measure up to Il.5 ft (3.5 m) of road width. The software is capable of automated data recording and post-process~ng, or real- t~me data processing of longitudinal or transverse profile and the TR] statistic. Longitudinal profile recording Intervals down to ~ in (25.4 mm) are available. Transverse profile measurement can be measured on the same frequency. With a single accelerometer, the software is capable of providing a response-type roughness index developed at the University of Texas (Walker 1991~. Using a combination of accelerometers and laser sensors, the Dynatest 5051 RSP system can provide real-time ~ values for each wheelpath and maximum "stringl~ne memos" rut values using the roadway cross section. Precise, high quality distance measurement Instrumentation is also provided. E-22

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Figure E-10. Dynatest 5051 Road Surface Profiler (Source: Dynatest Consulting, Inc.) FHWA PRORUT The PRORUT device was developed through an FHWA contract with the University of Michigan Transportation Research Institute (UMTRI) in 1983 (Gillespie and Sayers 1987~. PRORUT is an inertial profiling system that can be used to measure and record various roadway characteristics, including longitudinal pavement profiles, rutting, and roughness levels of the bow wheel tracks. The system is mounted In a van and uses commercially available components. Laser sensors and accelerometers are used to obtain the profile measurement in each wheel track. A centrally mounted laser sensor is also included for measuring the crown between Me wheel tracks and determining an average rut depth. The electronics and software system provide for two additional sensors so that Me rut depth in each wheel track can be measured, if desired. An IBM-compatible personal computer controls system operation and processes the data. The menu-driven software leads the operator through system calibration, component checks, and data collection. Data can Men be analyzed and presented graphically and numerically. The graphic records are useful in detailing the road profiles, and Me tabular output is preferable for listing Me International Roughness Index (IRI) and the mean rut depth averaged over selectable lengths of the test sections (Brown 1990~. E-23

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IMS Laser RST Propter Swedish The IMS Laser RST Profiler is a road surveying system developed by the Swedish National Road Adm~rustration. It can be used to measure longitudinal pavement profile, rut depth, megatexture, and macrotexture at a recording interval of ~ in (25.4 mm) or more. An accelerometer is used to establish an inertial reference plane, and roughness is measured continuously at speeds up to 55 mi/hr (90 km/hr). The roughness measurement output is IRI, although over roughness indices can be computed. A modification of this system has been used for ~ree-dimensional profile mapping. Figure E-~1 shows a version of the Laser RST system. Danish Road Institute ProfiIograph The Danish Road Institute (DRI) ProfiIograph was developed in 1990 and is quite similar to the Swedish device mentioned above, except Cat it is mounted in a car rather than in a small van. As shown in figure E-12, it has a vertical accelerometer, three aclditional accelerometers, two gyroscopes and one odometer, so that all six degrees (three translatoric and three rotoric) are evaluated. Road surface elevation is measured by up to 17 laser sensors mounted on a beam attached to the front of the vehicle. Lasers are also mounted at an angle on We extendable support bar to measure surface profile for the entire travel lane width. Because of the large number of accurate sensors and positioning instruments, this system can provide a large amount of Information. This includes lon~tud~nal and transverse surface profile, ruding, side slope, surface macrotexture (influencing fire noise), surface microtexture (influencing friction characteristics), and many profile- and response-related pavement smoothness indices. In 1994 the Danish Road Institute ProfiIograph Incorporated GPS technology using We GPS satellite navigation system to identify the vehicle's position within a few centimeters. clinometer-Based Profiling Systems Three manually propelled profiling systems have been developed using highly sensitive inclinometer sensors. The Face Dipstick was developed for smoothness measurement on ultra-smooth warehouse floors and later has been used for calibration of high-speed road profile systems. On the over hand, We CSC Profilair was intended as a replacement for rod-and-level profile measurement of airfield runways. The ARRB Walking Profiler was developed and manufactured by We Australian Road Research Board and is marketed In the United States by Trigg Industries International, Inc. for pavements, building slabs, and game courts as a World Bank Class ~ profile measuring device. These systems are discussed below. E-24

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Figure E-ll. Infrastructure Management Services Laser RST profiler. (Source: IMS) Figure E-12. DRI Profilograph system. (Source: Darrish Road Institute) E-25

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E.W. Face Dipstick The Dipstick (DIP = Digital Incremental Profiler) is a precision smoothness measuring device, operated by hand. Its shape is somewhat similar to a walking cane with a I-ft (0.3 m) long base, as shown In figure E-13. In the base is a vertical displacement measuring device that provides slope information to a small attached computer. By rotating the base end to end, an operator can move along a highway at 3-, 6-, 9-, or 12-in (7~, 152-, 229-, or 305-mm) Increments, determining Me surface profile, with a resolution of 0.001 in (0.025 mm). About 900 measurements can be made In an hour at 1-ft (0.3-m) increments. The computer and available software can produce a record of the profile measurements and also calculate an TRT, RMSVA, Mays Output, PSI, PRI, instantaneous vertical and angular acceleration, F-numbers (floor smoothness ratings), and cumulative deviation from a selected straightedge. Surface contours can be plotted, overlay thicknesses can be determined, and cumulative and running IR! can be computed and displayed. cot Begs It hands MEOW .11 1 L - d Gem ~ Ale Sod, feel a: filet Cat -Cat LEO , / ~ S - ah Kk#sor~d OIL ~3 Ad> Exam* ~ Figure E-13. Dipstick Auto-Read Profiler. (Source: Face Construction Technologies) E-26

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A 1991 study by the Center for Transportation concluded that "the manual-read version of the dipstick is an effective Class ~ profiling instrument, as long as operational techniques, including loop closing and repeat runs are followed. It is many times faster than the rod-and-level surveying method, and has a resolution 12 times better, making it an extremely accurate device" (Bertrand, Harrison, and Hudson 1991~. Class ~ profiling instruments are assumed to provide absolute elevation relative to true horizontal profile with less than I.5 percent bias. In highway applications, the Face Dipstick is used primarily to calibrate other types of smoothness measuring equipment and is also used to evaluate the smoothness of warehouse floors when smoothness is a critical factor In automated storage/retrieval operations. Because of its accuracy, the Dipstick has been used recently by the FHWA to provide a baseline profile for verification of high-speed profile system accuracy. CSC Profilair Developed in 1992 by Civil Structural Consultants (CSC) of North Vancouver, B.C. and commercially available in 1994, He CSC Profilair was originally designed to replace rod-and-level profile measurement of airport runways. The system, shown in figure E-14, is a gravity referenced device using an inclinometer for measuring the vertical angular deviation between adjacent elevation points. The elevation difference is then computed and added algebraically to He value of the previous elevation. Sensitivity of the angular measurement is based on a + 14.5 degree range digitized into + 4,096 units of angle, providing a static resolution of 0.001 in (0.025 mm). The 3-wheeled device is comprised of a metal structure that moves by rolling on solid balloon-type natural rubber tires. It can be divided into three 70-Ib (32 kg), or less, sections for airline or vehicle transportation. Immediately behind He steering wheel is a fourth wheel for recording He surface elevation. Data from the inclinometer attacher! to Cat wheel is stored on a 3.5 in (89 mm) floppy disk. The interval for testing is ~ ft (0.3 m), and the recommended rate of data collection is 5,000 ff/hr (0.42 m/s). Power for He inclinometer data collection system is supplied by a 12-voll bakery for up to ~ hours of operation, and power for forward movement is provided by the operator. At the conclusion of data collection, the disk can be removed and installed in a portable computer for computation of He profile and roughness Indices IRI and RMSVA. Bump criteria for selected baselength can be input before processing with the result that locations of out-of-tolerance bumps are marked on the profile and listed In a separate table. The software makes corrections for temperature and state of motion variations. To unprove accuracy, a reverse run is generally necessary, and the software is designed to adjust for these closed-loop profiles. E-27

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- ~- ~ ~- - l ~ ~ - ~ - 111 1 ~: ~ ~- ~ ~ s.- ~ ~ or ~ ~_ ~ 1 _ f ~ ~- ~ ~ - AL. _ ~ _ .:. - :' - - a :>x : 4:.~ - ~w I: x ~ ~ i: ~I -- ~ i: 1 ,: ~ :: :: ~: ::: ~ ~ :::: ::::: i: :::: : : ~ ::: : : ::: :: : :: :::::: : : : ::: :::: :: :: ~::::~: ::::: :: ~: ~ :~ :: : ~ : : ::: ::: ~ ~ ~ ~ ~ : : :, ::~ id: ~:: ::::::::::: ::~-: . ~a : ~::: ~- :: - ~ ::: :: : ::: ID_ : : :: : -~ ~ :: :::: :: ~ - ~ - .,,._: :: ::: : ::: :~. ~ Figure E-14. CSC Profilair. (Source: CSC Profilair) ARRB TR Lld. Walking Profiler The Walking Profiler, developed and manufactured by the Australian Road Research Board, is a multi-wheeled incI~nometer-based device that is pushed by the Operator at walking speed (1 km/hr [3,280 ft/hr]~. It continuously records the relative height of successive points at intervals of 241 mm (9.5 in), storing the vertical and horizontal deviation from the starting position in an onboard laptop computer. Software is available to compute and graph surface profiles and determine IRI. Accuracy reported by the manufacturer is +2 mm (0.0787 in) per 100 m (328 It) of horizontal distance. Other Profile and Smoothness Measuring Systems In addition to the above described pavement smoothness measuring devices, several other devices have been used for smoothness evaluations. These Include the ChIoe slope variance measuring system, Me Siometer accelerometer-based system, the Transportation Road Research Laboratory (TRRL) ProfiIometer, and the multifunctional ARAN pavement evaluation system. CHLOE Profits Developed at the AASHO Road Test during the late 1950s by Carey, Huckins, Leathers, and other engineers, Me ChIoe Profiler provides a "slope variance" (SV) statistic as a measure of pavement roughness, which in turn was intended to be used as an element of serviceability (Carey et al. 19621. Me Chioe Profiler is a relatively simple electrical-mechanical device. It is a trailered unit 25.5 it (7.8 m) long that measures the difference in angles between the 20-ft (6.! m) long trailer tongue and a small beam with two wheels, 9 in (229 mm) apart, recording the measured pavement slope at 6-~n (305-mm) increments. When in operation, the device is limited to a E-28

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speed of less than 5 mi/hr (8.0 km/hr) (Gillespie, Sayers, and Segal 1980; Carey et al. 1962). The gain from the CHLOE system is near 1.0 for wave numbers between 0.02 and 30 cycles/ft (0.006 and 98 cycles/m), and is less than 1.0 for higher wave numbers. A gain of 1.0 indicates prefect representation of the "true" pavement profile. This trueness to the actual slope profile is a positive advantage of the CHLOE system; however, the SV statistic is derived from an band of profile wave numbers much broader than is significant to an automotive vehicle, and as a result introduces a random error that degrades the agreement between RTRRM system output and SV (Gillespie, Sayers, and Segal 1980~. Walker Siomeler The Siometer accelerometer response device was developed at We University of Texas in the 1980s (Walker and Phung 1987~. Within the Texas SDHPT, the primary application of the Siometer is for evaluation of ride quality. The device became known as Me Siometer because its primary OUtDUt iS Me sewiceabili~ index (SI) for a particular pavement section. Currently, Me system consist of a sensor, a main control module, and a laptop computer for storing results. Included In the sensor system are an accelerometer, housed in a small case mounted vertically inside the trunk of a vehicle, and a distance measuring signal. The sensor unit and Me main control module cost $20,000 (1995~. -A - c, In 1995, the Siometer technology was incorporated into the Dvnatest Mode] 5051 RSP, described in an earlier section. This system provides a small van, a sensing accelerometer, hardware, and software for determining Me vehicle response-type roughness statistic. Including the test van, the 5051 RSP-R0.1 version is currently sold for about $41,000. - 1 - ~ . . .. - TRRL ProfiIometer Developed by the United Kingdom TRRL, the TRRL ProfiIometer originally consisted of a 2-wheeled trailer coupled to a lowing vehicle Jordan and Porter 1983~. The current system consists of a single vehicle into which is incorporated a beam encapsulated in foam and 15.4 ft (5 m) long, upon which four noncontact laser displacement transducers are mounted. Each transducer measures the vertical distance of pavement surface below the beam. The foam encapsulation inhibits the development of vertical temperature gradients in the beam, which would otherwise cause the beam to bend. Through a series of aigoriduns, He pavement surface profile is measured without He use of accelerometers or gyroscopes. . ~ ~ ~ ~ ~ ~ . ~ ~ ~ . ~ Reported capabilities of the equipment include measurement of longitudinal profile in either wheelpath, measurement of average rut depth, surface macrotexture measurement, and measurement of gradient, cross-fall, and radius of curvature. Windshield-mounted video cameras are also available. As reporter} by the manufacturer, the system is capable of accurately measuring pavement surface E-29

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wavelengths between 8 In (200 mm) and 493 it (150 m). accuracy is 0.5 percent. Distance measuring The equipment has been used to measure longitudinal profile on asphalt and concrete roads and airfields In bow the OK and continental Europe. It can operate at speeds from 3 to 62 mi/hr (5 to 100 km/hr). ARAN Profiler The Automatic Road Analyzer (ARAN) is a multi-function road quality surveying instrument. It is equipped with the following subsystems: (a) pavement surface roughness measurement, ebb rut clepth and transverse profile measurement, (c) gyro, (~) right-of-way video logging, (e) pavement condition video logging, and (f) pavement rating. System hardware Includes axle and body accelerometers, analog signal amplifiers, analog low-pass fillers, and a 12-bit analog to digital (A/D) converter. The software includes digital band-pass filters Passing wavelengths of 1 It ~_ ~ ~- ~ e e ~e ~bed ~ 1 ~ (A tO ;5tJU ~ (Ue;, m tO Yle4 m), alglta1 nlgn-pass nlters passing wavelengths of 2 It (Oe61 m) or less, and statistical models generating the reported roughness statistics RMSVA (roof mean square vertical acceleration), MAS (mean absolute sIope) and TEXTURE (surface texture) (Lu et al. 1994~. The current ARAN Laser SDP mode] provides surface profile, IRI, Serviceability Index (SI), and Ride Number output. The software is also capable of identifying must-grind locations, using algorithms developed by States. Accelerometers and laser-based distance measuring sensors are included In this self-calibrat~ng system mounted in a full-sized van. Smoothness Measuring Equipment of the Future What will be in Me future for pavement smoothness measuring equipment? Given Me rapid advances In technology, it would be hazardous to predict Me future. However, Improvements In accelerometers and gyroscopes advanced by Me space industry should make it possible to more accurately measure long wavelength (greater than 300 It [91.4 m]) surface deviations. Faster data collection systems, unproved data storage hardware, higher-speed computing capabilities, and better height sensing mechanisms should make it more possible to measure and evaluate megatexture (noise source) and microtexture (friction source) using noncontact profiling systems. Global positioning may be used to pinpoint areas of pavement roughness on maps that are linked to databases contouring construction, as well as maintenance and performance data for an entire States pavement inventory. As the capabilities of new equipment to measure pavement profiles Improve, the highway community will be unpolled to define the question, "How accurate is accurate enough?", especially in the area of new construction smoothness control. If drivers and vehicles do not respond negatively to very long or very short pavement surface wavelengths, it is not necessary for Crucial construction equipment to E-30

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accurately measure these wavelengths. Of course, other uses can be made of the new information made available by technological advances, including friction and noise evaluations, and highway agencies will use these advances to maintain high quality pavements In an era of shrinking budgets. E-31