1、Designation: E445/E445M 88 (Reapproved 2013)E445/E445M 15Standard Test Method forStopping Distance on Paved Surfaces Using a PassengerVehicle Equipped With Full-Scale Tires1This standard is issued under the fixed designation E445/E445M; the number immediately following the designation indicates the
2、yearof original 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 stopping
3、distance on paved surfaces with a passenger vehicle equipped withspecified full-scale automobile tires.1.2 This test method utilizes a measurement of stopping distances representing the non-steady state skid resistance on fourlocked wheels as the vehicle decelerates over a wetted pavement surface un
4、der specified limits of static wheel load and from adesired speed, while the vehicle remains essentially parallel to its original direction of motion.1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in eachsystem may not be exa
5、ct equivalents; therefore, each system shall be used independently of the other. Combining values from thetwo systems may result in non-conformance with the standard.1.4 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address allof the safe
6、ty concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriatesafety and health practices and determine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E178 Practice for Dealing With Out
7、lying ObservationsE274 Test Method for Skid Resistance of Paved Surfaces Using a Full-Scale TireE501 Specification for Rib Tire for Pavement Skid-Resistance TestsF403 Test Method for Tires for Wet Traction in Straight-Ahead Braking, Using Highway Vehicles (Withdrawn 2007)3F457 Test Method for Speed
8、and Distance Calibration of Fifth Wheel Equipped With Either Analog or Digital Instrumentation3. Summary of Test Method3.1 The test apparatus consists of a passenger vehicle with four wheels.4 The apparatus contains transducers, instrumentation,and a brake system for the four test wheels.ABS must no
9、t be functioning if so equipped. The test wheels are equipped withASTMPavement Test Standard Tires as specified in Specification E501.3.2 The pavement in the test lane is wetted. The test vehicle is brought above the desired test speed and is permitted to coastonto the wetted section until the prope
10、r speed is attained. The brakes are then promptly and forcefully applied to cause a quicklockup of the wheels and to skid to a stop. The resulting distance required to stop is recorded with the aid of suitableinstrumentation, and the speed of the test vehicle at the moment of brake application is no
11、ted.3.3 The skid resistance of the paved surface is determined from the resulting stopping distance measurement and test speed asstopping distance number, SDN, as determined from the equation given in 9.1, or as stopping distance, SD.NOTE 1Since speed has a significant effect on pavement surface ski
12、d resistance measurements, ranking and comparison of pavement surfaces athigher speeds might be considerably different from that at lower speeds.1 This test method is under the jurisdiction of ASTM Committee E17 on Vehicle - Pavement Systems and is the direct responsibility of Subcommittee E17.21 on
13、 FieldMethods for Measuring Tire Pavement Friction.Current edition approved Dec. 1, 2013Dec. 1, 2015. Published February 2014January 2016. Originally approved in 1971. Last previous edition approved in 20082013 asE445/E445M 88 (2008).(2013). DOI: 10.1520/E0445_E0445M-88R13.10.1520/E0445_E0445M-15.2
14、For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this historical standard is refe
15、renced on www.astm.org.4 Rizenbergs, R. L., and Ward, H. A., “Skid Testing With an Automobile,” Record No. 187, Highway Research Board, 1967.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous
16、 version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM Intern
17、ational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Significance and Use4.1 The knowledge of vehicle stopping distance serves as an additional tool in characterizing the pavement surface skidresistance. When used in conjunction with other physical and chem
18、ical tests, the skid resistance values derived from this testmethod may determine the suitability and adequacy of paving materials or finishing techniques. Improvements in pavementmaintenance practices and schedules may result from use of this test method.4.2 The stopping distance values measured by
19、 this test method with the equipment and procedures stated herein do notnecessarily agree or correlate directly with other methods of skid-resistance measurements.5,6 This test method is suitable forresearch and development purposes, where direct comparison between pavement surfaces are to be made w
20、ithin the same testprogram.5. Apparatus5.1 VehicleAfour-wheel passenger vehicle or a light truck preferably equipped with a heavy-duty suspension system. Vehiclesequipped with ABS are not acceptable unless there is a method of disabling the ABS when taking friction measurements.5.1.1 Braking SystemT
21、he four test wheels shall be equipped with suitable brakes. The brake system shall be capable of rapidlylocking the wheels and maintaining the locked-wheel condition throughout the test.5.1.2 Wheel LoadThe static wheel load of the vehicle shall not exceed the rated load of the ASTM Pavement Test Sta
22、ndardTire in accordance with Specification E501, and shall be as close to the stipulated load as possible. The vehicle gross weight shallnot be less than 3200 lb 1.45 mg.5.1.3 Tire and RimThe test tires shall be the ASTM Pavement Test Standard Tire as specified in Specification E501 mountedon a 15 b
23、y 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. The speed-indicating meters shall provide speed resolution and accuracy of 61.0 mph 61.5 km/h.Output shall be directly viewable by t
24、he operator and recorded if desired. The slewing rate of the fifth wheel shall be within thelimits described in Test Method F403. Other speed measuring devices are also acceptable as long as they meet the aboverequirements for resolution and accuracy.5.2.2 Distance-Measuring Transducer and CounterA
25、“fifth-wheel”-mounted transducer, producing at least 1 count per foot3 counts per metre, shall actuate a high-speed distance counter capable of accepting a count rate equivalent to the number ofcounts produced at the selected test speed, or the transducer output shall be recorded.NOTE 2The fifth whe
26、el assembly with speed and distance readouts should meet requirements specified in Test Method F457.5.2.3 Pressure-Sensitive SwitchApressure-sensitive switch, such as a hydraulic brake-light switch, requiring 70 to 90 psi 480to 620 kPa pressure to close, shall be installed in the wheel hydraulic bra
27、ke system to actuate the stopping-distance counter.6. Calibration6.1 SpeedCalibrate the test-vehicle speed indicator at the test speed by determining the time for traversing at constant speeda reasonably level and straight, accurately measured pavement at least 0.5 mile 0.8 km in length. Make a mini
28、mum of two speeddeterminations at the test speed. The speed shall be accurate to within 61 mph 61.5 km/h and repeatable to within 62 mph63.0 km/h when calibrated at 40 mph 65 km/h.6.2 DistanceCalibrate the distance transducer and counter by traversing at the approximate test speed a reasonably level
29、 andstraight, accurately measured pavement at least 0.5 mile 0.8 km in length. Initiate the calibration from a complete stop at thebeginning of the test course and terminate it by stopping at the end of the test course. Distance counter over 0.5-mile 0.8-km testcourse shall be within 63.0 ft 61.0 m
30、and repeatable to within a range of 64.0 ft 61.2 m when calibrated at 40 mph 65 km/h.Perform a minimum of two distance calibrations.6.3 Pressure-Sensitive SwitchSelect a pressure-sensitive switch responding to the specified pressure by testing in a hydraulicsystem equipped with a calibrated pressure
31、 transducer or gage having an accuracy of 63 % of the applied pressure.7. General7.1 Test VehicleCondition new tires by running them at rated inflation pressure on the test vehicle (or a similar vehicle) at amaximum speed of 50 mph 80 km/h for a distance not less than 200 miles 320 km before they ar
32、e used for test purposes.Afterconditioning, dynamically balance all tire and wheel assemblies. Inspect the tires for flat spots, damage, or other irregularities thatmay affect test results, and reject tires that have been damaged or worn beyond the wear line. The tire inflation pressure shall be24 6
33、 0.5 psi 165 6 3.5 kPa at ambient temperature (cold). Prior to each series of tests, warm-up the tires by traveling for at least5 miles 8 km at normal traffic speeds.5 Rizenbergs, R. L., “Florida Skid Correlation Study of 1967-Skid Testing with Automobiles,” Highway Skid Resistance, ASTM STP 456, AS
34、TM, 1969.6 Dillard, J. H., and Mahone, D. C., Measuring Road Surface Slipperiness, ASTM STP 366, ASTM, 1965.E445/E445M 1527.2 Test SectionsTest sections shall be defined as segments of the highway having a pavement of uniform age and uniformcomposition that has been subjected to essentially uniform
35、wear along its length. For instance, do not include sharp curves andsteep grades in the same test section with level tangent sections, and do not include passing lanes with traffic lanes. Make stoppingdistance measurements only on pavements that are free of obvious or unusual contamination.7.3 Test
36、SitesTest sites shall be defined as segments of test sections selected for stopping distance measurement, and shallinclude traffic lanes, or passing lanes, in both directions of travel.7.4 Lateral Positioning of Test Vehicle on HighwayNormally, perform test in the center of the wheel tracks of a tra
37、ffic laneof a highway. A stopping distance number may be quoted without qualification only if the test vehicle was so positioned duringthe test. If during the test, the vehicle moves outside the wheel tracks for more than 20 % of the stopping distance, or terminatesskidding off of the test lane, voi
38、d the test. 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 65 km/h. Tests may be made at other speeds but not less than 20 mph32 km/h. Initiate tests within 61.0 mph 61.5 km/h of the desired speed.7.5.
39、1 When the test speed is 40 mph 65 km/h, it is desirable, but not necessary, to cite the speed when quoting the test data.For all other speeds, including test speeds above 40 mph 65 km/h, the speed must be recorded. This may be done by adding tothe symbol as a subscript the numerals of the test spee
40、d in mph, that is, SDN30, or SD30, indicates stopping distance number, orstopping distance, at a test speed of 30 mph 48 km/h.8. Procedure8.1 Distance Counter ReadingSet the distance counter to zero prior to testing and record the total counts accumulated duringthe skid. If a strip-chart recorder is
41、 used for the purpose of measuring stopping distance, the recorded pulses may be counted later,but properly mark the chart or have the brake switch apply a mark to the chart when the switch closes.8.2 Pavement WettingWet the test lane at the test site just prior to skid testing using a water wagon e
42、quipped with spray baror other means of distributing water evenly and rapidly. Make two or more applications of water with a minimum coverage of 0.015gal/ft2 0.6 L/m2 6 15% per application until the surface is well-saturated (surface cavities are filled with water and runoff results).Wet a sufficien
43、tly long segment of the test lane to permit the test vehicle to skid on a wet surface and to allow the driver to adjustthe speed before brake application. Rewet the test lane between each test as required to maintain similar wetness conditions.8.3 After the pavement in the test lane is wetted, bring
44、 the vehicle above the desired test speed and permit it to coast(transmission gear in neutral) onto the wetted section until the proper speed is attained. Apply the brakes promptly and forcefullyto cause quick lockup of the wheels and to maintain a locked-wheel condition until the vehicle comes to a
45、 stop. Note the speedat the moment of brake application.9. Calculation9.1 Calculate the stopping-distance number for each test as follows:Inch-pound units:SDN5V2/30 SD! 3100 (1)Metric units:SDN5V2/255 SD! 3100# (2)where:V = speed of test vehicle at the moment of brake application, mph km/h, andSD =
46、stopping distance, ft m, (total count feet metres per count).9.2 The test results may also be expressed in terms of stopping distance, SD, in feet (or metres). Stopping distance obtainedwithin the permissible speed deviation may be corrected to the desired test speed by the following equation:Correc
47、ted SD5desired speed!2/actual speed!23actual SD (3)10. Number of Tests and Retests10.1 Skid Resistance of a Test SectionPerform at least three measurements of stopping distance in each test lane at a giventest site and at each selected test speed. Test no less than two sites in a test section. Consi
48、der the arithmetic average of the stoppingdistance numbers, or stopping distances, to the skid resistance of the test site. Consider the arithmetic average of the determinationfor test sites to be the skid resistance of the test section. If statistical or other criteria applied to the stopping dista
49、nce number, fora long test section indicate that it cannot be considered to be uniform, treat the section as two or more sections. For treatment ofthe results of faulty tests see 10.3.10.2 Skid Resistance of a Single LaneIf the skid resistance of a single lane at a given test site must be known, perform at leastsix measurements of stopping distance at each specified test speed.E445/E445M 15310.3 Faulty TestTests that are manifestly faulty or that give stopping distance numbers differing by more th
