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Designation: E 503/E 503M – 88 (Reapproved 2004

)

Standard Test Methods for

Measurement of Skid Resistance on Paved Surfaces Using
a Passenger Vehicle Diagonal Braking Technique1
This standard is issued under the fixed designation E 503/E 503M; the number immediately following the designation indicates the year
of 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 (e) indicates an editorial change since the last revision or reapproval.

1. Scope
1.1 These test methods cover the measurement of skid
resistance on paved surfaces with a passenger vehicle equipped
with specified full-scale vehicle tires and using the diagonal
braking mode. These test methods include the following:
1.1.1 Full-Stop Method—This represents the nonsteadystate skid resistance on two diagonally locked wheels, as the
vehicle decelerates over a wetted pavement surface under
specified limits of static wheel load and from a desired speed.
The vehicle shall remain essentially parallel to its original
direction of motion.
1.1.2 Pulse-Braking Method—The deceleration resulting
from momentary diagonal wheel lockup (pulse braking) is
measured. The vehicle decelerates over a wetted pavement
surface under specified limits of static wheel load and at a
desired speed. The vehicle shall remain essentially parallel to
its original direction of motion.
1.2 The values stated in either inch-pound units or SI units
are to be regarded separately as standard. Within the text, the
SI units are shown in brackets. The values stated in each
system are not exact equivalents: therefore, each system must
be used independently of the other. Combining values from the
two systems may result in nonconformance with the specification.

F 403 Test Method for Tires for Wet Traction in StraightAhead Braking, Using Highway Vehicles
F 457 Method for Speed and Distance Calibration of a Fifth
Wheel Equipped with Either Analog or Digital Instrumentation
3. Summary of Test Methods
3.1 The test apparatus for both test methods consists of a
passenger vehicle with four wheels, of which two are used for
test purposes. The apparatus contains transducers, instrumentation, and a selected brake system for the test wheels. The test
wheels are to be equipped with the Standard Pavement Test
Tires described in Specification E 501 or E 524.
3.2 For both test methods, the pavement in the test lane is
wetted with two applications from a water wagon equipped
with a spray bar or other means of distributing water evenly
and rapidly. The test vehicle is brought above the desired test
speed and permitted to coast onto the wetted section until
proper speed is attained. The brakes are then promptly and
forcefully applied to cause quick lock-up of the test wheels.
3.3 For the full-stop method, the vehicle operator maintains
brake application until a complete stop is obtained. The
resulting distance required to stop is recorded with the aid of
suitable instrumentation, and the velocity at the moment of
brake application is noted. The skid resistance of the paved
surface is determined from the resulting stopping distance
measurement and test speed as stopping distance number,
SDN, as determined from the equations given in Section 10, or
as stopping distance, SD.
3.4 For the momentary deceleration (pulse-braking)
method, the vehicle operator maintains the locked wheel
condition for approximately 1 s, and then releases the brakes.
The resulting deceleration during braking is recorded with the
aid of suitable instrumentation, and the velocity during brake
application is noted. The skid resistance of the paved surface is
determined from the resulting deceleration measurement and
test speed as diagonal braking number, DBN, as determined
from the equation given in Section 10.

2. Referenced Documents
2.1 ASTM Standards: 2
E 178 Practice for Dealing with Outlying Observations
E 501 Specification for Standard Rib Tire for Pavement
Skid-Resistance Tests
E 524 Specification for Standard Smooth Tire for Pavement
Skid-Resistance Tests
1
These test methods are under the jurisdiction of ASTM Committee E17 on
Vehicle-Pavement Systems and are the direct responsibility of Subcommittee
E17.21 on Field Methods for Measuring Tire Pavement Friction.
Current edition approved Dec. 1, 2004. Published December 2004. Originally
approved in 1982. Last previous edition approved in 2000 as E 503/E 503M – 88
(2000).
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [email protected] For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.

1

The accelerometer frequency response: direct current to minimum 10 Hz (flat 61.2. a reasonably level.1 The knowledge of vehicle stopping distance or deceleration serves as an additional tool in characterizing the pavement surface skid resistance. shall be mounted on each diagonal-braked wheel to provide indication of wheel lockup.8 km] in length.45 mg]. 5.8 km) in length.2 Distance—Calibrate the distance transducer and counter by traversing. 4. requiring 70 to 90 psi [480 to 620 kPa] pressure to close. recorded.5 mile (0. ranking and comparison of pavement surfaces at higher speeds might be considerably different from that at lower speeds. The vehicle gross weight shall not be less than 3200 lb [1. 5.6 Low-Pass Filter—To minimize vehicle and roadway related vibrations from effecting the deceleration data. The slewing rate of the fifth wheel shall be within the limits described in Test Method F 403. 5. −3 dB at 9 6 1 Hz and rolloff at between 12 and 24 dB per octave. Calibration 6.7 Multichannel Recorder—If a multichannel recorder is used during tests with either method. or the transducer output shall be recorded. a “fifth-wheel”-mounted transducer.1. and accurately measured pavement at least 0. 5.2 The stopping distance or deceleration values measured by these two test methods with the equipment and procedures stated herein do not necessarily agree or correlate directly with other methods of skid-resistance measurements. Apparatus 5.6 Safety Equipment—Vehicle lighting and signing shall conform to local requirements.1 Vehicle—The vehicle shall be a four-wheel passenger car or a light truck.5 km/h] and repeatable to within 62 mph [63. capable of providing at least 1 count per revolution. ranking and comparison of pavement surfaces using the Specification E 501 test tire might be considerably different from that using the Specification E 524 test tire.3 Wheel Load—The static wheel load of the vehicle shall not exceed the rated load of the Standard Tire for Pavement Tests in accordance with Specification E 501 or E 524 and shall be as close to the stipulated load as possible.2 Distance-Measuring Transducer and Counter—For the full-stop method.2. The filter shall be flat 62 % from direct current to 5 Hz.2. and shall be maintained to provide at least 80 % of “new” tread depth. meter readings shall be monitored by test observer in vehicle.0 mph [61. These test methods are suitable where direct comparison between pavement surfaces are to be made within the same test program. 5.4 Steering System—Power steering is recommended to minimize control requirements that might result from brake application. 5. 4.1. Transducer output shall be recorded. Improvements in pavement maintenance practices and schedules may result from use of these test methods. a reasonably level. NOTE 2—Since speed has a significant effect on pavement surface skid-resistance measurements. Output shall be directly viewed by operator. When used in conjunctionwith other physical and chemical tests.2. the skid resistance values derived from these test methods may determine the suitability and adequacy of paving materials or finishing techniques.2 Braking System—The brake system shall be capable of rapidly locking the diagonal test wheels and maintaining a locked-wheel condition throughout the test. the recorder should meet the requirements specified in Test Method F 403.1 Speed—Calibrate the speed indicator of the test vehicle at the test speed by determining the time for traversing. 5.2.4 Pressure-Sensitive Switch—A pressure-sensitive switch. at the approximate test speed.2 Instrumentation: 5.5 mile [0. Initiate the calibration from a complete stop at the beginning of the test course and terminate by stopping at 2 . an accelerometer. straight. Make a minimum of two speed determinations at the test speed.01 g. at constant speed. NOTE 1—Since tire-tread design has a significant effect on pavement surface skid-resistance measurements.2. straight. The test vehicle shall be equipped with appropriate brake system cut-off valves. The speed shall be accurate to within 61 mph [61.0 km/h] when calibrated at 40 mph [65 km/h].5 Tire and Rim—The test tires shall be the Standard Tire for Pavement Tests of Specification E 501 or E 524 mounted on a 15 by 6 JJ rim.1. preferably equipped with a heavy-duty suspension system. shall be installed in the wheel hydraulic brake system to actuate the stoppingdistance counter. and accurately measured pavement at least 0. 5.E 503/E 503M – 88 (2004) recorded if desired.8 Power Supply—The power supply for transducers and recorder (optional) should meet requirements specified by transducer and recorder manufacturers. Output shall be directly viewed by the operator and 6. either manual or electric to prevent brake actuation on the diagonal wheel pair not equipped with test tires. 5. ranged to 61 g full scale and mounted near the vehicle center of gravity to measure longitudinal deceleration of the vehicle.1.3 Vehicle Test Wheel Revolutions—Pulse transducers. or both. and capable of accepting a count rate equivalent to the number of counts produced at the test speed.1. or tachometer generators.2. 5. meeting specifications given in Test Method F 403. Significance and Use 4.1. such as a hydraulic brake-light switch. producing at least 1 count per foot [3 counts per metre] shall actuate a high-speed distance counter. 5. 5.1 Rear Axle—Posi-traction or other limited-slip differentials must not be used. a low-pass filter shall be connected to the signal output of the accelerometer. 5. 6.0 %). Unbraked wheels of the test vehicle shall be equipped with standard production tread designs. visible to the operator. shall provide deceleration resolution and accuracy of 60.5 Acceleration-Measuring Transducer or Meter—For the momentary deceleration (pulse-braking) method. 5.1 Vehicle Speed-Measuring Transducer and Indicator— The transducer shall be a “fifth-wheel”-mounted tachometer generator or pulse transducer and speed-indicating meters shall provide speed resolution and accuracy of 61. NOTE 3—The fifth wheel assembly with speed and distance readouts should meet requirements specified in Method F 457.5 km/h]. 5.2.

02 g when statically calibrated as specified below. Test Speed 8. recording the accelerometer output at each increment. 9.1 Test Vehicle—Install test tires on one front and one rear wheel diagonally. A stopping distance number.6 L/m2] 615% per application until the surface is well-saturated (surface cavities are filled with water and runoff results). rotate the pendulum-type accelerometer in 5° increments up to 30 6 0. 7. 6. Then apply the brakes promptly and forcefully to cause quick lock-up of the wheels and to maintain the locked-wheel condition until the vehicle comes to a stop. verify proper output during the vehicle speed calibration procedure described in 6.5-mile [0. The tire inflation pressure shall be 24 6 0. while allowing the other tires to remain free rolling. or terminates skidding off the test lane. may be quoted without qualification only if the test vehicle was so positioned during the test.3 Vehicle Test Wheel Revolutions—If pulse transducers are used. but not necessary. stopping distance.2 m] when calibrated at 40 mph [65 km/h]. When the test speed is 40 mph. or other irregularities that may affect the results. that is SDN30. but properly mark the chart or have the brake switch apply a mark to the chart when the switch closes.5.2 Pendulum Type—By using a known accurate inclinometer.5 km/h] of the desired speed.5 Accelerometer—The accelerometer shall be accurate to within 60. runway touchdown areas and taxi areas.E 503/E 503M – 88 (2004) the end of the test course. the vehicle moves outside the wheel tracks for more than 20 % of the stopping distance. damage. it is desirable. calibrate in accordance with the manufacturer’s specifications.8-km] test course shall be within 63.1.5 psi [165 6 3. 9. Warm up the tires by traveling for at least 5 miles [8 km] at normal traffic speeds. or stopping distance. Use a similar pair of test tires with the same tread type and condition.1 Electronic Transducer Type—Conduct calibration of transducer-type accelerometer statically by tilting the accelerometer on a rotary table or another test fixture to incrementally increased or decreased angles with respect to a true horizontal plane and record the accelerometer output values for each angle by observing the chart trace deflections on the recorder used in testing.2 Pulse Braking Test Method: NOTE 4—Marking and comparing pavement surfaces at different water depths may vary considerably since surface water depth has a significant effect on pavement skid-resistance measurements. Adjust vehicle brake system cut-off valves to brake only diagonal test tires.5 kPa] at ambient temperature (cold). The accelerometer output in gs should agree with the tangent of the angle within 60. 7.015 gal/ft2 [0. SD30. Perform a minimum of two distance calibrations.3 Test Sites—Test sites shall be defined as segments of test sections selected for stopping distance or deceleration mea3 .4 Pressure-Sensitive Switch—Select a pressure-sensitive switch responding to the specified pressure by testing it in a hydraulic system equipped with a calibrated pressure transducer or gage having an accuracy of 63 % of the applied pressure.01 g and repeatable to within 60.1 Distance Counter Reading—Set the distance counter to zero prior to testing and record the total counts accumulated during the skid. Condition new tires by running them at their rated inflation pressure on the test vehicle (or a similar vehicle) at a maximum of 50 mph (80 km/h) for a distance not less than 200 miles [320 km] before using them for test purposes. and shall include highway traffic lanes.4. or diagonal braking number at a test speed of 30 mph [48 km/h]. Make two or more applications of water with a minimum coverage of 0. If testing cannot be conducted in the prescribed manner. If tachometer generators are used.0 mph [61. inspect the tires for flat spots. Distance counter over a 0. during the test.4 Pavement Wetting—Wet the test lane at the test site just prior to skid testing using a water wagon equipped with a spray bar or other means of distributing water evenly and rapidly. the test speed must be stated. do not include sharp curves and steep tangent sections in the same segment with level tangent sections. 8. in both directions of travel.01 g at each increment. the recorder pulses may be counted later. to cite the speed when quoting test data. 6. or passing lanes.1 The standard test speed for both the full-stop and pulse-braking methods shall be 40 mph [65 km/h]. 6. surement. For all other speeds. Bring the vehicle above the desired test speed and permit it to coast (transmission gear in neutral) onto the wetted section until proper speed is attained.0 m] and repeatable to within a range of 64 ft [61. Follow accelerometer calibration steps specified in Test Method F 403. Note the speed at the moment the brake is applied. the numerals of the test speed in mph.2 Test Sections—Test sections shall be defined as segments of the highway or runway having a pavement of uniform age and uniform composition that has been subjected to essentially uniform wear along its length. Dynamically balance all tire and wheel assemblies. Prior to each series of tests. 6. or DBN3 0 indicates stopping distance number.3 Wet the pavement in the test lane at the test site as outlined in 7.5. void the test. Initiate tests within 61. test in the center of the wheel tracks of a traffic lane of a highway.1. Tests may be made at other speeds but not less than 20 mph (32 km/h).2°.1 Full-Stop Test Method: 9.2 Lateral Position of Test Vehicle on Highway— Normally.1. Preparation 9. Wet a sufficiently long segment of the test lane to permit the test vehicle to skid on wet surface and to allow the driver to adjust speed before brake application. If. Rewet the test lane between tests as required to maintain similar wetness conditions. 9. 7. If a strip-chart recorder is used for the purpose of measuring stopping distance. and reject tires which have been damaged or worn beyond the wear line. 7. This may be done by adding to the symbol as a subscript. and do not include passing lanes with traffic lanes. Procedure 9. 6.1. 7. identify the test data accordingly.0 ft [61. For instance. Conduct the test immediately after the water truck clears the test area.

1 Field Report— The field report for each test section shall contain data on the following items: 12. perform at least six measurements of stopping distance or deceleration at each test speed. SDN.1.2 Skid Resistance of a Single Lane—If the skid resistance of a single lane at a given test site must be known. If statistical or other criteria applied to the stopping distance numbers or diagonal braking numbers for a long test section indicate that it cannot be considered to be uniform. cloud cover. mph. DBN.6 Tire type (for each test). 9.2 If a recorder is used. 11. (4) where: a = average locked-wheel deceleration corrected for the vehicle free-rolling drag acceleration.1 Accelerometer Reading—If a pendulum-type accelerometer is used. Then apply the brakes promptly and forcefully to cause quick lockup of the wheels.1.E 503/E 503M – 88 (2004) 9. 12. Report 12.3 Weather conditions (principally temperature.1.2. [m] (total count 3 metres per count). Number of Tests and Retests 11. The arithmetic average of either the stopping distance numbers or diagonal braking numbers shall be considered to be the skid resistance of the test section. the section shall be treated as two or more sections.2 Pulse-Braking Test Method: 10. 1 Pulse-Braking Deceleration determination of the average differential deceleration between free-rolling and locked-wheel test conditions requires a separate test run to obtain the average free-rolling deceleration level through the same speed range and with similar surface conditions as measured during the locked-wheel test run. set the accelerometer to zero prior to testing and record the deceleration level measured during the pulse braking skid. The test results may also be expressed in terms of stopping distance. measured in units of feet [metres].1 Skid Resistance of a Test Section—Perform at least three measurements of skid resistance using either method in each test lane at a given test site and at each selected test speed. Note the speed at the moment the brakes are applied and released and the deceleration level measured if a pendulum-type accelerometer is used.1. Bring the vehicle above the desired test speed and permit it to coast (transmission gear in neutral) onto the wetted section until proper speed is attained. as measured by an accelerometer is determined from the equation: DBN 5 2a 3 100 12.5 SD! 3 100 11. NOTE 5—If an electronic transducer-type accelerometer is used.1.1. (2) where: V = speed of test vehicle at the moment of brake application. Test no less than two sites in a test section. but properly identify the records. the recorded deceleration output may be determined later. turn it on prior to the start and turn it off after completing the vehicle test run. 1.1 Full-Stop Test Method: 10. (1) where: V = speed of test vehicle at the moment of brake application. 12. If an electronic transducer-type accelerometer is used. for each test as follows: SDN 5 ~V 2/15 SD! 3 100 FIG. the values of free-rolling deceleration before and after the locked-wheel portion of the test run are available for correcting locked-wheel deceleration values as denoted by the typical oscillograph-record accelerometer trace shown in Fig.5 Test speed (for each test). For treatment of the results of faulty tests see 11. 9.4 Location of each test site and lanes tested. [km/h].4.2 Date and time of day. ft (total count 3 feet per count) or SDN 5 ~V2/127. 11. 12. and SD = stopping distance.3 Faulty Tests—Tests that are manifestly faulty or that give stopping distance numbers or diagonal braking numbers differing by more than 5 SDN or DBN from the average of all tests in the same test section shall be treated in accordance with Recommended Practice E 178.1 Calculation of Stopping Distance Number— Calculate the stopping distance number. 12.1 Location and identification of test sections.2.3. If a pendulum-type accelerometer is used. Stopping distance obtained within the permissible speed deviation may be corrected to the desired test speed by the equation: Corrected SD 5 ~desired speed!2/~actual speed!2 3 actual SD (3) 10.3 Wet the pavement in the test lane at the test site as outlined in 7. Calculation 10. SD. 12.1 Calculation of Diagonal Braking Number— Pavement diagonal braking number.2.1. and wind). 10. 4 . and SD = stopping distance. release the brakes and convert to four-wheel braking to bring the vehicle into position for the next test. maintain locked wheel condition for approximately 1 s.2.

11 Average stopping distance number(s).8 Stopping distance number. are entirely their own responsibility. West Conshohocken. if values are reported that were not used in computing the test section average. 12. 100 Barr Harbor Drive. 610-832-9555 (fax). As a result. PO Box C700. 12. stopping distance.2. If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards.7 Average traffic speed (or speed mix as in the case of grade with heavy truck traffic). United States. this fact shall be so stated. Stopping number data obtained with the same operator and under identical test conditions should not be considered suspect unless they differ by more than 5 %. and the risk of infringement of such rights.2.1 Location and identification of test section. and 13. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised. 5 . Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters. 12.1.2 The analysis of available data obtained with an experienced operator indicates that repeated tests using both the full-stop and the pulse-braking test methods show repeatability or agreement within 65 % of the average value.2.8 Date and time of day. either reapproved or withdrawn. 12. condition and aggregate type (specify source if available).6 Average daily traffic for each year since pavement construction.org (e-mail). Precision and Bias 13.4 Pavement type. at the address shown below.2. This standard is copyrighted by ASTM International.1 The relationship of observed SDN and DBN units to some “true” value of locked-wheel sliding friction has not been established at this time.2.astm.9 Weather conditions. tire and speed(s) at which reported average was obtained (highest and lowest average values for test sites may be reported). mix design of surface course. 12. only repeatability is given for these test methods.7 Accelerometer type (for each test). 12.2.10 Lane tested. 12. 12. which you may attend.2 Number of lanes and presence of lane separators. PA 19428-2959.3 Grade and alignment. or through the ASTM website (www. 12. 12. or [email protected] stopping distance(s). or diagonal braking number (for each test). Users of this standard are expressly advised that determination of the validity of any such patent rights. and 12.2.2.2.org).5 Age of pavement.1. or diagonal braking number(s) for test section. 13. Your comments will receive careful consideration at a meeting of the responsible technical committee.2. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the above address or at 610-832-9585 (phone). ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard.2.E 503/E 503M – 88 (2004) 12.2 Summary Report—The summary report shall include for each test section data on the following items as far as they are available and pertinent to the variables or combination of variables under investigation: 12. 12.