ASTM_E_2341_-_E_2341M_-_05_2014.pdf

Designation:E2341/E2341M05(Reapproved 2014)Standard Test Method forDetermining the Stopping Distance Number by Initial Speedand Stopping Distance at Traffic Incident Sites1This standard is issued under the fixed designation E2341/E2341M;the number immediately following the designation indicates the 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 determination of an averagestopping distance number(SDN)under the conditions that thismethod was executed.The experimental conditions are gener-ally intended to be similar to those of a specified trafficincident.The data from this method is not comparable tomeasured distances of a specified traffic incident vehicle thatcannot be shown to have continuous,full application of itsbraking system.1.2 This test method determines the SDN from the mea-sured stopping distance and initial speed when the wheels onspecified axles are braked in the same manner as the specifiedtraffic incident vehicle.The evaluation vehicles braking sys-tem is required to duplicate the specified incident vehicle forboth type(conventional,partial ABS,or full ABS)and func-tionality(all brakes functional or not).1.3 The method documents the test conditions as a basis forevaluating their similarity to conditions of a specified trafficincident.1.4 The values stated in either inch-pound units or SI unitsare to be regarded separately as standard.Within the test,the SIunits are shown in brackets.The values stated in each systemare not exact equivalents;therefore,each system must be usedindependently of the other.Combining values from the twosystems may result in nonconformance with the specification.1.5 This standard may involve hazardous materials,operations,and equipment.This standard does 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 Standards:2E178 Practice for Dealing With Outlying ObservationsE274 Test Method for Skid Resistance of Paved SurfacesUsing a Full-Scale TireF403 Test Method for Tires for Wet Traction in Straight-Ahead Braking,Using Highway Vehicles(Withdrawn2007)3F457 Test Method for Speed and Distance Calibration ofFifth Wheel Equipped With Either Analog or DigitalInstrumentation3.Summary of Test Method3.1 The test apparatus consists of a vehicle and tires similarto the traffic incident vehicle and instruments to measure andrecord initial speed and stopping distance.If the incidentvehicle did not have ABS and the test vehicle does,the ABSmust be disabled.3.2 The test is performed on the roadway where the trafficincident occurred with surface conditions similar to those thatexisted at the time of the traffic incident.3.3 The test vehicle is brought above the desired test speedand permitted to coast onto the test section.The brakes are thenvery quickly and forcefully applied to cause immediate lock-upof all desired wheels and to skid to a stop(note:if the car isequipped with ABS,lock-up will not be obtained).In eithercase the initial speed at brake application,the stoppingdistance,and tire mark lengths are recorded.If tire marks donot vary smoothly in darkness,width or density,the variationin appearance needs to be described.3.4 The deceleration of the roadway/vehicle combination,called the stopping distance number(SDN),is determined from1This test method is under the jurisdiction of ASTM Committee E17 on Vehicle-Pavement Systems and is the direct responsibility of Subcommittee E17.21 onField Methods for Measuring Tire Pavement Friction.Current edition approved Dec.1,2014.Published December 2014.Originallyapproved in 2005.Last previous edition approved in 2009 as E2341/E2341M 05(2009).DOI:10.1520/E2341_E2341M-05R14.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 the measured stopping distance and the initial speed.SDNdiffers from skid resistance since it includes other factors suchas grade,air resistance,and rolling resistance,especially fornon-locked wheels.NOTE1Since speed has a significant effect on pavement surface skidresistance measurements,the SDN can be expected to be considerablydifferent at higher speeds from that at lower speeds as well.Generally,theSDN can be expected to decrease with increasing speed.4.Significance and Use4.1 The SDN determined by this