ASTM E445-15(R2019) pdf free download

ASTM E445-15(R2019) pdf free download.Standard Test Method for Stopping Distance on Paved Surfaces Using a Passenger Vehicle Equipped with Full-Scale Tires
1. Scope
1.1 This test method covers the measurement of stopping distance on paved surfaces with a passenger vehicle equipped with specified full-scale automobile tires. 1.2 This test method utilizes a measurement of stopping distances representing the non-steady state skid resistance on four locked wheels as the vehicle decelerates over a wetted pavement surface under specified limits of static wheel load and from a desired 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 each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.5 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Summary of Test Method
3.1 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 not be functioning if so equipped. The test wheels are equipped with ASTM Pavement 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 coast onto the wetted section until the proper speed is attained. The brakes are then promptly and forcefully applied to cause a quick lockup of the wheels and to skid to a stop. The resulting distance required to stop is recorded with the aid of suitable instrumentation, and the speed of the test vehicle at the moment of brake application is noted. 3.3 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 equation given in 9.1, or as stopping distance, SD. N OTE 1—Since speed has a significant effect on pavement surface skid resistance measurements, ranking and comparison ofpavement surfaces at higher speeds might be considerably different from that at lower speeds.
6. Calibration
6.1 Speed—Calibrate the test-vehicle speed indicator at the test speed by determining the time for traversing at constant speed a reasonably level and straight, accurately measured pavement at least 0.5 mile [0.8 km] in length. Make a minimum of two speed determinations at the test speed. The speed shall be accurate to within 61 mph [61.5 km/h] and repeatable to within 62 mph [63.0 km/h] when calibrated at 40 mph [65 km/h]. 6.2 Distance—Calibrate the distance transducer and counter by traversing at the approximate test speed a reasonably level and straight, accurately measured pavement at least 0.5 mile [0.8 km] in length. Initiate the calibration from a complete stop at the beginning 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] test course shall be within 63.0 ft [61.0 m] 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 Switch—Select a pressure-sensitive switch responding to the specified pressure by testing in a hydraulic system equipped with a calibrated pressure trans- ducer or gage having an accuracy of 63 % of the applied pressure.