ASTM_E_2467_-_05_2012.pdf

Designation:E246705(Reapproved 2012)Standard Practice forDeveloping Axle Count Adjustment Factors1This standard is issued under the fixed designation E2467;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This standard practice describes techniques for adjustingobserved or assumed axle counts so that they will representcorresponding estimated vehicle counts as part of roadwaytraffic monitoring.1.2 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and to determine theapplicability of regulatory limitations prior to use.2.Referenced Documents2.1 Other:TrafficMonitoringGuide,U.S.DepartmentofTransportation,FederalHighwayAdministration,Washington,DC 205903.Terminology3.1 Definitions:3.1.1 axle,naxis oriented transversely to the nominaldirection of vehicle motion,and extending the full width of thevehicle,about which the axle wheels at both ends rotate.3.1.2 axle count,ntotal number of vehicle axles that areenumerated at a point on a lane or roadway during a specifiedtime interval.3.1.3 axle counter,ndevice that receives signals from anaxle sensor and indicates the cumulative number of axles thatwere detected by the sensor during a specified time interval.3.1.4 functional classification,na stratification of high-ways based on their common usage or function.3.1.5 machine count,nthe cumulative number of axles,vehicles,or vehicles within specified classes,or all of these,indicated or recorded by a traffic recording device for aspecified time interval.3.1.6 traffc counter,na device that indicates,and usuallyrecords,the number of vehicles or vehicle axles,or both,thatpass a point on a lane or roadway during a specified timeinterval.3.1.7 traffc recording device,na device that receivessignals from a sensor(s)and registers axle count,vehicle count,vehicle classification count,speed,gap,or headway(any or allof these)for defined time intervals.3.1.8 vehicle,nan assembly of one or more mobile unitscoupled together for travel on a highway;a vehicle comprisesone powered unit and may include one or more unpoweredfull-trailer or semi-trailer unit(s).3.1.9 vehicle classification,nthe process of categorizingvehicles into various classes,usually according to their respec-tive axle or mobile-unit(s)configuration.3.1.10 vehicle classification count,nthe cumulative num-ber of vehicles of each defined class indicated or recorded fora specified time interval.3.2 Definitions of Terms Specific to This Standard:3.2.1 axle count adjustment factor,nthe number that whenmultiplied by an axle count(3.1.2)will adjust the axle count toan estimate of the total number of vehicles that produced theaxle count.3.2.1.1 DiscussionThe adjustment factor is sometimesbased upon the premise that(1)the portion of all vehiclesincluded in each of various vehicle classes,and(2)therespective average number of axles per vehicle class for thevehicles that produced the axle count being adjusted are knownor are assumed to be the same as the two corresponding valuesused to characterize the vehicles in a chosen,representative,orsimilar traffic stream.4.Summary of Practice4.1 Basic StepsDevelopment of an axle count adjustmentfactor involves two basic steps:(1)defining a time intervalalong with the characteristics of the vehicles that comprised thetraffic stream during the time interval,and(2)obtaining thedata needed to characterize the vehicles in the traffic stream.Depending upon the type of data available,one of the follow-ing methods may be used to calculate the factor.4.1.1 Direct MethodIf,for a chosen time interval,re-corded data are available(e.g.,from anASTM Type I and TypeII WIM system or from certain types of traffic counters or1This practice is under the jurisdiction of ASTM Committee E17 on Vehicle-Pavement Systems and is the direct responsibility of Subcommittee E17.52 onTraffic Monitoring.Current edition approved July 1,2012.Published July 2012.DOI:10.1520/E2467-05R12.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 traffic recordings devices)concerning the total number ofvehicles in the traffic stream concurrently with the total axlecount(3.1.2),the axle count adjustment factor can be calcu-lated directly as the ratio of the two numbers.The total numberof vehicles in the traffic stream may be determined from arecorded machine count(3.1.5)or by summating the number ofvehicles in each applicable vehicle class as recorded in avehicle classification count(3.1.10).This method of derivingan axle count adjustment factor is illustrated in Appendix A asAppendix X2.4.1.2 Alternative MethodIf specific