1、Designation: E2415 05 (Reapproved 2012)Standard Practice forInstalling Piezoelectric Highway Traffic Sensors1This standard is issued under the fixed designation E2415; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las
2、t 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 practice covers the installation of piezoelectrictire-force sensors that are used to detect axles when counting,clas
3、sifying, or weighing vehicles as part of a roadway trafficmonitoring program. Piezoelectric sensors are often used inpairs and combined with other roadway sensors such asinductive loops to classify and weigh vehicles.1.2 The practice applies only to piezoelectric tire-forcesensors used for the detec
4、tion of vehicle axles on a roadway.1.3 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are for informa-tion only and are not considered standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its u
5、se. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E867 Terminology Relating to Vehicle-Pavement SystemsE1318 Specification f
6、or Highway Weigh-In-Motion (WIM)Systems with User Requirements and Test MethodsE1442 Practice for Highway-Traffic Monitoring (Withdrawn2001)3E1572 Practice for Classifying Highway Vehicles fromKnown Axle Count and Spacing (Withdrawn 2002)3E1957 Practice for Installing and Using Pneumatic Tubeswith R
7、oadway Traffic Counters and Classifiers3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 axleaxis oriented transversely to the nominal direc-tion of vehicle motion and extending the full width of thevehicle, about which the wheels at both ends rotate.3.1.2 axle countnumber of ve
8、hicle axles that are enumer-ated at a point on a lane or roadway during a specified timeinterval.3.1.3 axle countera device that receives signals from anaxle sensor and indicates the cumulative number of axles thathave been detected by the sensor during a specified timeinterval.3.1.4 axle spacinghor
9、izontal distance between the centerof a vehicle axle and that of the preceding axle on the vehicle.3.1.5 machine countcumulative 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 traf
10、fc counterdevice 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 deviceunit that receives outputfrom a sensor(s) and registers axle count, vehicle count, vehicleclassifi
11、cation count, speed, gap, or headway (any or all ofthese) for defined time intervals.3.1.7.1 DiscussionA traffic recording device may alsorecord axle load and gross-vehicle weight. Refer to Specifica-tion E1318.3.1.8 vehicleone, or multiple, mobile unit(s) designed fortravel upon a roadway; a vehicl
12、e comprises one powered unitand may include one or more non-powered trailer or semitrailerunit(s).3.1.9 vehicle classification countcumulative number ofvehicles of each defined type (class) indicated or recorded fora specified time interval.4. Summary of Practice4.1 Site Selection:4.1.1 Select a rel
13、atively straight and smooth section ofroadway that is expected to have free flowing traffic throughoutthe duration of the data collection session.4.1.2 The selected roadway section should have little to nosurface distortion or rutting in the wheel paths.1This practice is under the jurisdiction of AS
14、TM 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/E2415-05R12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custome
15、r 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, Wes
16、t Conshohocken, PA 19428-2959. United States14.1.3 Longitudinal grades and lateral pavement slopesshould be less than 3 % as per Specification E1318.4.1.4 The selected site should have:4.1.4.1 Access to electrical power or good location for solarand telephone service if data is to be collected conti
17、nuously formore than a few weeks at a time,4.1.4.2 Adequate space for an instrument cabinet, with asafe area for a technician to park a vehicle and stand whilemaking adjustments or repairs, and4.1.4.3 Adequate drainage to prevent standing water insplice boxes and instrument cabinet.4.1.5 Traffic con
18、ditions at the site should include minimaloccurrences of stop-and-go traffic, slow-moving traffic, lanechanging, and passing on two-lane roads.4.1.6 Pavement cracks and joints shall be avoided. Do notplace a sensor across any crack or joint. Whenever practicable,space sensors a minimum of 1 ft (300
19、mm) from transversecracks and contraction joints and 6 ft (1800 mm) fromexpansion joints.4.1.7 Pavement thickness and strength must be adequate tosustain the additional stress concentrations that will result frominstallation of piezoelectric and other associated sensors.4.1.8 Site requirements for i
20、nstalling weigh-in-motion(WIM) systems are given in Specification E1318.4.2 Installation Procedures:4.2.1 Installation should be performed in relatively goodweather, avoiding extreme heat or cold and moisture conditionsthat might adversely affect the bonding of grout to the sensoror the pavement.4.2
21、.2 At the selected site, use a taut string line or a templateoriented perpendicular to the flow of vehicular traffic to markthe sensor locations.4.2.2.1 Colored spray paint applied over the string line ortemplate will provide a more lasting guide for pavementcutting than chalk or crayon.4.2.3 Use a
22、pavement saw or similar equipment with acompetent operator to make the necessary parallel cuts in thepavement.4.2.3.1 The width and depth of the cut shall be in accor-dance with the recommendations of the manufacturer of thesensor.4.2.3.2 When feasible, use a saw blade of proper thicknessor gang sev
23、eral thinner blades together to cut the sensor slot inone pass. If two cuts are made for installation, use a hammerand chisel or a small jackhammer to loosen and clean out allmaterial between the two cuts to the required depth.4.2.3.3 Wash the slot and adjacent surface with clean water,using a high-
24、pressure washer. Assure that no contaminatedwash water remains in the slot. Dry the slot and adjacent roadsurface using compressed air and a blowgun. The air compres-sor should have a dedicated outlet for the hose and be able tosustain a minimum flow rate of approximately 185 ft3/min (5m3/min).An ai
25、r drier/oil remover unit should be installed at thecompressor outlet. Use a dedicated 50-ft (15-m) section ofairline hose for this process. Make sure that all dirt andmoisture is removed from the hose before use.4.2.3.4 Inspect the slot, and use a wire brush or a chisel todislodge any debris that ma
26、y still be clinging to its sides andbottom. Again, use compressed air to remove any remainingdebris from the slot.4.2.3.5 After unpacking any type of piezoelectric sensoron-site, test its output signal according to the manufacturersinstructions, making sure the sensor is working properly.4.2.3.6 Tes
27、t slot length, depth, and width by lowering thesensor or an accurate template into the slot and look for contactpoints on the ends, bottom, and sides of the slot.Adjust the sizeas needed.4.2.4 When cutting slots for lead-in-wire runs to the edge ofthe pavement, including the paved shoulder, make eve
28、ry effortto avoid unnecessary horizontal angles and turns.4.2.5 It is recommended that the sensor lead-in wires be ofsufficient length to reach into the equipment cabinet withoutsplicing. When a splice must be made, use an approvedunderground wiresplice encapsulation kit in accordance withthe kit ma
29、nufacturers instructions. This helps ensure thatmoisture will not enter the wire and render the piezoelectricsensor unusable until the splice is replaced. Splices should behoused only in junction and splice boxes. Splices should bestructurally strong, electrically sound, and waterproof. Splicinggene
30、rally requires a well-trained, certified electrician. He orshe shall follow the manufacturers instructions or standardprocedures, carefully and exactly.4.2.6 Cover the pavement surface along both sides of theslot with a three-inch (75-mm) wide strip of gaffers tape orduct tape.4.2.7 It is extremely
31、important to always handle the sensorcarefully. When installing bare (not-encapsulated) sensors,never handle the sensor without new, powder-free vinyl orlatex examination gloves. This keeps the oil from ones handsfrom contaminating the exposed surface of the sensor. Thelead-in wire is especially vul
32、nerable to being pulled away fromthe sensor element inside. Never bend the sensor so as to breakit or so as to form a kink in it.4.2.8 The exposed surfaces of a bare sensor should be“roughed up” using a medium grade emery cloth or sandpaper.4.2.9 Clean the exposed surfaces of a bare sensor of any di
33、rtor oily substance with acetone, denatured alcohol, or othersimilar zero-residue solvent that will not harm the surface orthe lead-in wire insulation and will not interfere with theadhering properties of the selected grout.4.2.10 Use a grout recommended by the sensormanufacturer, or one specificall
34、y approved by the sensor user,that will adhere well to the sensor and pavement material andwhich will cure quickly so as not to delay traffic at the siteduring installation. Many grout problems stem from incorrectproportions, improper mixing, or entraining air during themixing process. Consideration
35、 may be given to using adual-canister pneumatic applicator that combines both groutcomponents in an exact mix during the application process,thereby reducing errors commonly experienced with handmixing.E2415 05 (2012)24.2.11 Prior to mixing grout or beginning grout application,test the sensor output
36、 signal again according to the manufac-turers instructions, making sure that the sensor is workingproperly.4.2.12 Prepare, handle, and finish the grout in accordancewith the recommendations of the sensor manufacturer.4.2.13 Use grouting procedures recommended by the manu-facturer to insure that air
37、voids are not present. Higher-viscosity grouts are more likely to trap air under the sensor.4.2.14 Following the instructions of the manufacturer, placethe sensor in the pavement slot, adjusting its height so that thetop of the sensor is positioned according to the manufacturersspecifications. This
38、is usually accomplished by using bracketsand or jigs to hold the sensor at the correct height.4.2.15 With the sensor correctly held in place, carefully fillthe pavement slot with grout.4.2.16 For a bare sensor, use a putty knife, trowel or similartool, to smooth the grout so that it is flush or just
39、 above the roadsurface. The top of the finished grout surface shall not be belowthe road surface. It is better to leave too much grout and grindthe excess away after it has fully cured than to leave adepression in the roadway that will degrade the sensor signal.4.2.17 When the grout has partially cu
40、red, carefully removethe tape and any additional fixtures from the adjacent pavementsurface.4.2.18 It may be necessary to use an angle or belt grinder tofinish the grout so that it is flush with the road surface. Ensurethat the grout is fully cured prior to grinding and to opening thelane to traffic
41、.4.2.19 Route the lead-in wires through the sawn lead-inslots and conduit to the equipment cabinet or to the splice box,making sure not to kink or nick the outer protective insulation(see 4.2.5). Use additional grout or sealant to fill lead wire slotscompletely to edge of pavement.4.2.20 With the se
42、nsor and lead-in wires in place, test theoutput signal at the cabinet according to the manufacturersinstructions, making sure that the sensor is working properly.4.3 Post Installation Testing:4.3.1 Use an oscilloscope to observe the piezoelectric sen-sor output signal for proper signal strength, goo
43、d signal-to-noise ratio, and clean pulses when vehicles pass over thesensor.4.3.2 For applications other than weigh-in-motion, once thepiezoelectric sensor(s) have been installed and connected to asuitable traffic recording device, a verification count must bemade to determine whether the sensor out
44、put signals are beingrecorded correctly. There should be a mix of vehicles, includ-ing those with light, medium and heavy axle loads that willnormally pass over the sensor(s).4.3.3 To make the verification (machine) count, initializethe traffic recording device (that is, note the indicated axlecount
45、) and then concurrently have one or more persons countand record manually (manual or validation count) the numberof axles that pass over the sensor(s) until at least 50 axles havepassed. After this, note the indicated machine count (verifica-tion count) on the traffic recording device and calculate
46、thenumber of axles counted concurrently with the manual count.Compare the machine count with the manual count(s) (valida-tion count(s) to verify that the axle counts were determinedcorrectly. If more than one person made a manual count, thereshall be no more than 2 % difference from the largest valu
47、e forany count to be acceptable for use in determining the validationcount. Repeat the manual counts (and the machine countsconcurrently) as necessary until this condition is satisfied; thencalculate the mean value of all manual counts and round themean value to the nearest integer. Use this integer
48、 value as thevalidation count. For acceptable performance, the machine(verification) count should not vary from the validation countmore than 4 %, preferably less. Do not begin a data-collectionsession until the piezoelectric sensor(s) and the associatedtraffic recording device are performing accept
49、ably.4.3.4 Recheck the piezoelectric sensor output with an oscil-loscope 24 to 48 h later.4.4 Maintenance:4.4.1 Because of the discontinuity created by cutting the slotfor the sensor and lead-in wires, the pavement structure in thevicinity of the sensors is subject to more severe stresses fromtire loads than that on the rest of the roadway. A greaterpotential for accelerated pavement and sensor damage exists;therefore, frequent and careful attention must be given to thecondition of the pavement surrounding the sensors and to theproper functioning of the sensors.4.
