1、Designation: E 445/E 445M 88 (Reapproved 2008)Standard Test Method forStopping Distance on Paved Surfaces Using a PassengerVehicle Equipped With Full-Scale Tires1This standard is issued under the fixed designation E 445/E 445M; the number immediately following the designation indicates the yearof or
2、iginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of stoppingdistance o
3、n paved surfaces with a passenger vehicle equippedwith specified full-scale automobile tires.1.2 This test method utilizes a measurement of stoppingdistances representing the non-steady state skid resistance onfour locked wheels as the vehicle decelerates over a wettedpavement surface under specifie
4、d limits of static wheel loadand from a desired speed, while the vehicle remains essentiallyparallel to its original direction of motion.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents
5、; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.4 This standard may involve hazardous materials, opera-tions, and equipment. This standard does not purport toaddress all of the safety concerns, if
6、 any, associated with itsuse. It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 178 Practice for Dealing With Outlying Observat
7、ionsE 274 Test Method for Skid Resistance of Paved SurfacesUsing a Full-Scale TireE 501 Specification for Rib Tire for Pavement Skid-Resistance TestsF 403 Test Method for Tires for Wet Traction in Straight-Ahead Braking, Using Highway Vehicles3F 457 Test Method for Speed and Distance Calibration ofF
8、ifth Wheel Equipped With Either Analog or DigitalInstrumentation3. Summary of Test Method3.1 The test apparatus consists of a passenger vehicle withfour wheels.4The apparatus contains transducers, instrumen-tation, and a brake system for the four test wheels. The testwheels are equipped withASTM Pav
9、ement Test Standard Tiresas specified in Specification E 501.3.2 The pavement in the test lane is wetted. The test vehicleis brought above the desired test speed and is permitted to coastonto the wetted section until the proper speed is attained. Thebrakes are then promptly and forcefully applied to
10、 cause aquick lockup of the wheels and to skid to a stop. The resultingdistance required to stop is recorded with the aid of suitableinstrumentation, and the speed of the test vehicle at themoment of brake application is noted.3.3 The skid resistance of the paved surface is determinedfrom the result
11、ing stopping distance measurement and testspeed as stopping distance number, SDN, as determined fromthe equation given in 9.1, or as stopping distance, SD.NOTE 1Since speed has a significant effect on pavement surface skidresistance measurements, ranking and comparison of pavement surfaces athigher
12、speeds might be considerably different from that at lower speeds.4. Significance and Use4.1 The knowledge of vehicle stopping distance serves as anadditional tool in characterizing the pavement surface skidresistance. When used in conjunction with other physical andchemical tests, the skid resistanc
13、e values derived from this testmethod may determine the suitability and adequacy of pavingmaterials or finishing techniques. Improvements in pavementmaintenance practices and schedules may result from use ofthis test method.4.2 The stopping distance values measured by this testmethod with the equipm
14、ent and procedures stated herein do notnecessarily agree or correlate directly with other methods ofskid-resistance measurements.5,6This test method is suitable1This test method is under the jurisdiction of ASTM Committee E17 on Vehicle- Pavement Systems and is the direct responsibility of Subcommit
15、tee E17.21 onField Methods for Measuring Tire Pavement Friction.Current edition approved June 1, 2008. Published July 2008. Originally approvedin 1971. Last previous edition approved in 2001 as E 445 88 (2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custo
16、mer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4Rizenbergs, R. L., and Ward, H.A., “Skid Testing With anAutomobile,” RecordNo. 187, Highway Research Board, 1967.5Rizenbergs, R. L., “Flori
17、da Skid Correlation Study of 1967-Skid Testing withAutomobiles,” Highway Skid Resistance, ASTM STP 456, ASTM, 1969.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.for research and development purposes, where direct compari-son betwee
18、n pavement surfaces are to be made within the sametest program.5. Apparatus5.1 VehicleAfour-wheel passenger vehicle or a light truckpreferably equipped with a heavy-duty suspension system.5.1.1 Braking SystemThe four test wheels shall beequipped with suitable brakes. The brake system shall becapable
19、 of rapidly locking the wheels and maintaining thelocked-wheel condition throughout the test.5.1.2 Wheel LoadThe static wheel load of the vehicleshall not exceed the rated load of the ASTM Pavement TestStandard Tire in accordance with Specification E 501, and shallbe as close to the stipulated load
20、as possible. The vehicle grossweight shall not be less than 3200 lb 1.45 mg.5.1.3 Tire and RimThe test tires shall be the ASTMPavement Test Standard Tire as specified in SpecificationE 501 mounted on a 15 by 6 JJ rim.5.2 Instrumentation:5.2.1 Vehicle Speed-Measuring Transducer and IndicatorThe trans
21、ducer shall be a “fifth wheel”-mounted tachometergenerator or transducer. The speed-indicating meters shallprovide speed resolution and accuracy of 61.0 mph 61.5km/h. Output shall be directly viewable by the operator andrecorded if desired. The slewing rate of the fifth wheel shall bewithin the limi
22、ts described in Test Method F 403.5.2.2 Distance-Measuring Transducer and CounterA“fifth-wheel”-mounted transducer, producing at least 1 countper foot 3 counts per metre, shall actuate a high-speeddistance counter capable of accepting a count rate equivalent tothe number of counts produced at the se
23、lected test speed, or thetransducer output shall be recorded.NOTE 2The fifth wheel assembly with speed and distance readoutsshould meet requirements specified in Test Method F 457.5.2.3 Pressure-Sensitive SwitchA pressure-sensitiveswitch, such as a hydraulic brake-light switch, requiring 70 to90 psi
24、 480 to 620 kPa pressure to close, shall be installed inthe wheel hydraulic brake system to actuate the stopping-distance counter.6. Calibration6.1 SpeedCalibrate the test-vehicle speed indicator at thetest speed by determining the time for traversing at constantspeed a reasonably level and straight
25、, accurately measuredpavement at least 0.5 mile 0.8 km in length. Make aminimum of two speed determinations at the test speed. Thespeed shall be accurate to within 61 mph 61.5 km/h andrepeatable to within 62 mph 63.0 km/h when calibrated at40 mph 65 km/h.6.2 DistanceCalibrate the distance transducer
26、 and counterby traversing at the approximate test speed a reasonably leveland straight, accurately measured pavement at least 0.5 mile0.8 km in length. Initiate the calibration from a complete stopat the beginning of the test course and terminate it by stoppingat the end of the test course. Distance
27、 counter over 0.5-mile0.8-km test course shall be within 63.0 ft 61.0 m andrepeatable to within a range of 64.0 ft 61.2 m whencalibrated at 40 mph 65 km/h. Perform a minimum of twodistance calibrations.6.3 Pressure-Sensitive SwitchSelect a pressure-sensitiveswitch responding to the specified pressur
28、e by testing in ahydraulic system equipped with a calibrated pressure trans-ducer or gage having an accuracy of 63 % of the appliedpressure.7. General7.1 Test VehicleCondition new tires by running them atrated inflation pressure on the test vehicle (or a similar vehicle)at a maximum speed of 50 mph
29、80 km/h for a distance notless than 200 miles 320 km before they are used for testpurposes. After conditioning, dynamically balance all tire andwheel assemblies. Inspect the tires for flat spots, damage, orother irregularities that may affect test results, and reject tiresthat have been damaged or w
30、orn beyond the wear line. The tireinflation pressure shall be 24 6 0.5 psi 165 6 3.5 kPa atambient temperature (cold). Prior to each series of tests,warm-up the tires by traveling for at least 5 miles 8 km atnormal traffic speeds.7.2 Test SectionsTest sections shall be defined as seg-ments of the hi
31、ghway having a pavement of uniform age anduniform composition that has been subjected to essentiallyuniform wear along its length. For instance, do not includesharp curves and steep grades in the same test section withlevel tangent sections, and do not include passing lanes withtraffic lanes. Make s
32、topping distance measurements only onpavements that are free of obvious or unusual contamination.7.3 Test SitesTest sites shall be defined as segments of testsections selected for stopping distance measurement, and shallinclude traffic lanes, or passing lanes, in both directions oftravel.7.4 Lateral
33、 Positioning of Test Vehicle on HighwayNormally, perform test in the center of the wheel tracks of atraffic lane of a highway. A stopping distance number may bequoted without qualification only if the test vehicle was sopositioned during the test. If during the test, the vehicle movesoutside the whe
34、el tracks for more than 20 % of the stoppingdistance, or terminates skidding off of the test lane, void thetest. If testing cannot be conducted in the prescribed manner,identify the test data accordingly.7.5 Test SpeedThe standard test speed shall be 40 mph 65km/h. Tests may be made at other speeds
35、but not less than 20mph 32 km/h. Initiate tests within 61.0 mph 61.5 km/h ofthe desired speed.7.5.1 When the test speed is 40 mph 65 km/h, it isdesirable, but not necessary, to cite the speed when quoting thetest data. For all other speeds, including test speeds above 40mph 65 km/h, the speed must b
36、e recorded. This may be doneby adding to the symbol as a subscript the numerals of the testspeed in mph, that is, SDN30,orSD30, indicates stoppingdistance number, or stopping distance, at a test speed of 30mph 48 km/h.6Dillard, J. H., and Mahone, D. C., Measuring Road Surface Slipperiness, ASTMSTP 3
37、66, ASTM, 1965.E 445/E 445M 88 (2008)28. Procedure8.1 Distance Counter ReadingSet the distance counter tozero prior to testing and record the total counts accumulatedduring the skid. If a strip-chart recorder is used for the purposeof measuring stopping distance, the recorded pulses may becounted la
38、ter, but properly mark the chart or have the brakeswitch apply a mark to the chart when the switch closes.8.2 Pavement WettingWet the test lane at the test site justprior to skid testing using a water wagon equipped with spraybar or other means of distributing water evenly and rapidly.Make two or mo
39、re applications of water with a minimumcoverage of 0.015 gal/ft20.6 L/m2 6 15% per applicationuntil the surface is well-saturated (surface cavities are filledwith water and runoff results). Wet a sufficiently long segmentof the test lane to permit the test vehicle to skid on a wetsurface and to allo
40、w the driver to adjust the speed before brakeapplication. Rewet the test lane between each test as requiredto maintain similar wetness conditions.8.3 After the pavement in the test lane is wetted, bring thevehicle above the desired test speed and permit it to coast(transmission gear in neutral) onto
41、 the wetted section until theproper speed is attained. Apply the brakes promptly andforcefully to cause quick lockup of the wheels and to maintaina locked-wheel condition until the vehicle comes to a stop.Note the speed at the moment of brake application.9. Calculation9.1 Calculate the stopping-dist
42、ance number for each test asfollows:Inch-pound units:SDN 5 V2/30 SD! 3 100 (1)Metric units:SDN 5 V2/255 SD! 3 100 (2)where:V = speed of test vehicle at the moment of brake appli-cation, mph km/h, andSD = stopping distance, ft m, (total count 3 feet metresper count).9.2 The test results may also be e
43、xpressed in terms ofstopping distance, SD, in feet (or metres). Stopping distanceobtained within the permissible speed deviation may be cor-rected to the desired test speed by the following equation:Corrected SD 5 desired speed!2/actual speed!23 actual SD (3)10. Number of Tests and Retests10.1 Skid
44、Resistance of a Test SectionPerform at leastthree measurements of stopping distance in each test lane at agiven test site and at each selected test speed. Test no less thantwo sites in a test section. Consider the arithmetic average ofthe stopping distance numbers, or stopping distances, to theskid
45、resistance of the test site. Consider the arithmetic averageof the determination for test sites to be the skid resistance of thetest section. If statistical or other criteria applied to thestopping distance number, for a long test section indicate thatit cannot be considered to be uniform, treat the
46、 section as twoor more sections. For treatment of the results of faulty tests see10.3.10.2 Skid Resistance of a Single LaneIf the skid resis-tance of a single lane at a given test site must be known,perform at least six measurements of stopping distance at eachspecified test speed.10.3 Faulty TestTe
47、sts that are manifestly faulty or thatgive stopping distance numbers differing by more than 5 SDNfrom the average of all tests in the same test section shall betreated in accordance with Practice E 178.11. Reports11.1 Field ReportThe field report for each test sectionshall contain data on the follow
48、ing items:11.1.1 Location and identification of test sections,11.1.2 Date and time of day,11.1.3 Weather conditions, principally temperature, cloudcover, and wind,11.1.4 Location of each test site and lanes tested,11.1.5 Test speed (for each test), and11.1.6 Stopping distance number, or stopping dis
49、tance (foreach test).11.2 Summary ReportThe summary report shall includefor each test section, data on the following items as far as theyare available and pertinent to the variables or combinations ofvariables under investigation:11.2.1 Location and identification of test section,11.2.2 Number of lanes and presence of lane separators,11.2.3 Grade and alignment,11.2.4 Pavement type, mix design of surface course, condi-tions, and aggregate type (specify source if available),11.2.5 Age of pavement,11.2.
