1、Designation: E 445/E 445M 88 (Reapproved 2001)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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of stoppingdistance
3、on 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 specifi
4、ed 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 inch-pound units or SI unitsare to be regarded separately as standard. Within the text, theSI units are shown in brackets. The val
5、ues stated in eachsystem are not exact equivalents; therefore, each system mustbe used independently of the other. Combining values from thetwo systems may result in nonconformance with the specifi-cation.1.4 This standard may involve hazardous materials, opera-tions, and equipment. This standard do
6、es not purport toaddress all of the safety concerns, if 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 Stand
7、ards:E 178 Practice for Dealing with Outlying Observations2E 274 Test Method for Skid Resistance of Paved SurfacesUsing a Full-Scale Tire3E 501 Specification for Standard Rib Tire for PavementSkid-Resistance Tests3F 403 Test Method for Tires for Wet Traction in Straight-Ahead Braking, Using Highway
8、Vehicles4F 457 Test Method for Speed and Distance Calibration of aFifth Wheel Equipped with Either Analog or DigitalInstrumentation43. Summary of Test Method3.1 The test apparatus consists of a passenger vehicle withfour wheels.5The apparatus contains transducers, instrumen-tation, and a brake syste
9、m for the four test wheels. The testwheels are equipped with ASTM Pavement 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 spe
10、ed is attained. Thebrakes are then promptly and forcefully applied to 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
11、The skid resistance of the paved surface is determinedfrom the resulting 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 skidresistanc
12、e measurements, ranking and comparison of pavement surfaces athigher 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
13、conjunction with other physical andchemical tests, the skid resistance 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
14、 stopping distance values measured by this testmethod with the equipment and procedures stated herein do notnecessarily agree or correlate directly with other methods ofskid-resistance measurements.6,7This test method is suitable1This test method is under the jurisdiction of ASTM Committee E17 onVeh
15、icle-Pavement Systems and is the direct responsibility of Subcommittee E17.21on Field Methods for Measuring Tire Pavement Friction.Current edition approved Feb. 1, 1988. Published March 1988. Originallypublished as E 445 71 T. Last previous edition E 445 82.2Annual Book of ASTM Standards, Vol 14.02.
16、3Annual Book of ASTM Standards, Vol 04.03.4Annual Book of ASTM Standards, Vol 09.02.5Rizenbergs, R. L., and Ward, H. A., “Skid Testing With an Automobile,” RecordNo. 187, Highway Research Board, 1967.6Rizenbergs, R. L., “Florida Skid Correlation Study of 1967-Skid Testing withAutomobiles,” Highway S
17、kid 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 between pavement surfaces are to be made within the sametest program.5. Apparatu
18、s5.1 VehicleA four-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 of rapidly locking the wheels and maintaining thelocked-wheel condition
19、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 as possible. The vehicle grossweight shall not be less than 3200 lb 1.45
20、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 transducer shall be a “fifth wheel”-mounted tachometergenerator or transducer.
21、 The speed-indicating meters shallprovide speed resolution and accuracy of 61.0 mph61.5km/h. Output shall be directly viewable by the operator andrecorded if desired. The slewing rate of the fifth wheel shall bewithin the limits described in Test Method F 403.5.2.2 Distance-Measuring Transducer and
22、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 selected test speed, or thetransducer output shall be recorded.NOTE 2The fif
23、th 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 480 to 620 kPa pressure to close, shall be installed inthe wheel hydrauli
24、c 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, accurately measuredpavement at least 0.5 mile 0.8 km in length. Make ami
25、nimum 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 and counterby traversing at the approximate test speed a reasonably level
26、and 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 counter over 0.5-mile0.8-km test course shall be within 63.0 ft 61.0 m an
27、drepeatable 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 pressure by testing in ahydraulic system equipped with a calibrated pressure tran
28、s-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 80 km/h for a distance notless than 200 miles 320 km before they are used
29、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 worn beyond the wear line. The tireinflation pressure shall be 24 6 0.5 psi
30、 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 highway having a pavement of uniform age anduniform composition that has bee
31、n 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 stopping distance measurements only onpavements that are free of obvious or
32、 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 Positioning of Test Vehicle on HighwayNormally, perform test in the cente
33、r 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 wheel tracks for more than 20 % of the stoppingdistance, or terminates skiddi
34、ng 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 but not less than 20mph 32 km/h. Initiate tests within 61.0 mph61.5 km/h o
35、fthe 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 be recorded. This may be doneby adding to the symbol as a subscript the nume
36、rals of the testspeed in mph, that is, SDN30,orSD30, indicates stoppingdistance number, or stopping distance, at a test speed of 30mph 48 km/h.7Dillard, J. H., and Mahone, D. C., Measuring Road Surface Slipperiness, ASTMSTP 366, ASTM, 1965.E 445/E 445M28. Procedure8.1 Distance Counter ReadingSet the
37、 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 later, but properly mark the chart or have the brakeswitch apply a mark to the chart wh
38、en 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 more applications of water with a minimumcoverage of 0.015 gal/ft20.6 L/m2 6 15% per ap
39、plicationuntil 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 allow the driver to adjust the speed before brakeapplication. Rewet the test lane between
40、 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 the wetted section until theproper speed is attained. Apply the brakes promptly andf
41、orcefully 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-distance number for each test asfollows:Inch-pound units:SDN 5 V2/30 SD! 3 100 (1)Metric
42、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 expressed in terms ofstopping distance, SD, in feet (or metres). Stopping distanceobt
43、ained 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 Resistance of a Test SectionPerform at leastthree measurements of stopping distance
44、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 resistance of the test site. Consider the arithmetic averageof the determination for
45、 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 section as twoor more sections. For treatment of the results of faulty tests see10.
46、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 TestTests that are manifestly faulty or thatgive stopping distance numbers differing by mo
47、re 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 following items:11.1.1 Location and identification of test sections,11.1.2 Date and time o
48、f 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 distance (foreach test).11.2 Summary ReportThe summary report shall includefor each tes
49、t 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,11.2.6 Average daily traffic (for each year since pavementconstruction),11.2.7 Average traffi
