1、Designation: E2561 07a (Reapproved 2018)Standard Practice for theInstallation of Inductive Loop Detectors1This standard is issued under the fixed designation E2561; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last r
2、evision. 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 describes the recommended procedure forinstalling inductive loop detectors in sawed slots in roadwaypavement f
3、or use as a traffic monitoring device or to actuatetraffic control devices such as a traffic signal. Although thepractice is not intended for installing preformed loops, thepractice does contain information of value for this type of loop,such as recommendations for the number of turns of loop wire,n
4、umber and direction of twists in the lead-in wire and cable,splice location (if needed), and grounding options.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand ar
5、e not considered standard.1.3 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, health, and environmental practices and deter-mine the applicability of regulator
6、y limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organi
7、zation TechnicalBarriers to Trade (TBT) Committee.2. Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 electronics unit, na card or free-standing modulethat transmits energy into the wire loops, typically at frequen-cies between 20 kHz and 100 kHz; special applications such asvehic
8、le classification may use electronics units that transmit atfrequencies above 100 kHz; electronics units allow control ofsensitivity, frequency, pulse or presence operation, and timingfeatures (that is, delay and extension) in some models andindicate system failures.2.1.2 inductance, nproperty of an
9、 electric circuit or oftwo neighboring circuits that generates an electromotive forcein one circuit when the current changes in that circuit or in theneighboring circuit; expressed in units of Henrys (H).2.1.3 inductive loop detector, nthose parts of an inductiveloop detector system that consist of
10、the wire loops, lead-inwires, and lead-in cable and which respond to the passage orpresence of a vehicle with a decrease in inductance of the wireloop.2.1.4 inductive loop detector system, na sensor to detectvehicles and their traffic flow properties, whose major compo-nents are: (1) one or more tur
11、ns of insulated loop wire woundin a slot sawed in the pavement, (2) lead-in wires extendingfrom the loop wire to a curbside or shoulder pull box, (3)lead-in cable spliced to the lead-in wires that extends from thepull box to the controller cabinet, and (4) electronics unithoused in the controller ca
12、binet.2.1.5 insulation resistance, nthe resistance measured witha megohmmeter between a conductor and the outer insulatingjacket of a wire or cable.2.1.6 lead-in cable, nshielded wire that is spliced to thelead-in wires in the pull box and which extends from the pullbox to the controller cabinet, wh
13、ere it is connected to theelectronics unit; also known as home-run cable, transmissionline, or feeder cable.2.1.7 lead-in wires, na continuation of the loop wire thatruns from the physical edge of the loop to the pull box; usuallytwisted together to form a wire pair.2.1.8 loop system sensitivity, ns
14、mallest change of induc-tance at the electronics unit terminals that will result in a signalthat indicates the passage or presence of a vehicle.2.1.9 loop wire, none-conductor insulated wire used forboth the wire loop and the lead-in wire; may be jacketed orencased in tube.2.1.10 pull box, na contai
15、ner that encloses the splicesbetween the lead-in wires and the lead-in cable; when installedunderground, the removable cover is aligned flush with theground surface; also known as a handhole, splice box, orjunction box.2.1.11 quadrupole loop, ntypically a rectangular wireloop configuration with a lo
16、ngitudinal slot extending along the1This 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 on, Sept. 1, 2018. Published September 2018. Origi-nally approved in 20
17、07. Last previous version approved in 2012 as E2561 07a(2012). DOI: 10.1520/E2561-07AR18.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles
18、 on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1center of the loop so that the wire can be installed in afigure-eight pattern; t
19、he quadrupole loop produces four elec-tromagnetic poles instead of the normal two, thus improvingthe sensitivity to small vehicles and minimizing splashover;quadrupole loops are also used in a diagonal configuration todetect bicycles (1).22.1.12 saw cut, nopening made in the roadway pavementusing a
20、pavement saw into which the wire loop or lead-in wiresare inserted; also referred to as a slot.2.1.13 splashover, nunwanted actuation caused by a ve-hicle in a lane adjacent to the lane in which a sensor is located.2.1.14 traffc monitoring device, nequipment that maycount and classify vehicles and m
21、easure vehicle flow charac-teristics such as vehicle speed, lane occupancy, turningmovements, and other parameters typically used to portraytraffic movement.2.1.15 wire loop, none or more turns of loop wire woundin a slot sawed in the pavement.3. Summary of Practice3.1 The major steps in installing
22、an inductive loop detectorsystem are:3.1.1 Preparing plans and specifications,3.1.2 Securing the work zone,3.1.3 Installing underground conduit and pull box,3.1.4 Cutting a slot for the loop wire and lead-in wires,3.1.5 Installing the wires,3.1.6 Twisting the lead-in wires,3.1.7 Testing for proper o
23、peration of the wire loop andlead-in wires,3.1.8 Sealing the saw cuts,3.1.9 Splicing the lead-in wires to the lead-in cable in a pullbox,3.1.10 Connecting the lead-in cable to the terminal strip inthe cabinet,3.1.11 Testing for proper operation of the wire loop, lead-inwires, and lead-in cable assem
24、bly, and3.1.12 Connecting the terminal strip to the electronics unit.3.2 Procedures needed to ensure work zone safety, trafficcontrol, and installation of conduit, pull box, controller cabinet,and any equipment usually placed in the cabinet, such as theelectronics unit, are not covered by this pract
25、ice.4. Significance and Use4.1 This practice provides a method for the in-road instal-lation of an inductive loop detector that consists of wire loops,lead-in wires, and lead-in cable. The practice is intended forinstalling wires in saw cuts made in the roadway surface andnot for installing preforme
26、d loops that may be encased in aprotective enclosure such as plastic conduit. Typical compo-nents of an inductive loop detector system are illustrated in Fig.1. Modern inductive loop detector electronic units are capableof detecting vehicles even if the wire loop is laid on reinforcingsteel before c
27、oncrete is placed.5. Procedure5.1 Scale drawings of the installation site showing thegeometry of the roadway and the exact location of thecomponents of the inductive loop detector in relation to thepavement or lane markings are required. The drawings shallindicate the location and specifications for
28、 the wire loop(typically centered in the middle of the lane) and lead-in wires,lead-in cable, pull boxes, conduit, power sources, pavementmaterials and sealants, cabinets, and electronic units requiredfor the installation. The accuracy of the drawings has a primaryeffect on the quality of the instal
29、lation, as it provides funda-mental guidance for the installation crew and becomes part ofthe procurement package used to acquire the needed compo-nents.5.2 The dimensions of the loops and number of turns areselected according to the types of vehicles to be detected,vehicle undercarriage height, lan
30、e width, length of lead-incable, and, for some applications, the data desired. Inductiveloops should not be wider than 6 ft (183 cm) in a 12-ft(366-cm) lane. Loops should not be less than 5 ft (152 cm)wide because the detection distance between the road surfaceand the vehicle undercarriage becomes l
31、imited, as the detectiondistance is approximately equal to one-half to two-thirds of theloop width (such as, the minimum loop dimension). Since theinductance of the loop must be greater than the inductance of2The boldface numbers in parentheses refer to the list of references at the end ofthis pract
32、ice.FIG. 1 Inductive Loop Detector System (Notional) (2)E2561 07a (2018)2the lead-in cable (that is, 21 H per 100 ft (69 H per 100 m)of #14 AWG lead-in cable) for the loop system to havesufficient sensitivity, Klein et al. (2) recommend that theinductance of single loops and series, parallel, or ser
33、ies-parallelcombinations of loops be greater than 50 mH to ensure stableoperation of the inductive loop detector system. Guidance forthe number of turns needed to produce the required inductancevalue is found in Klein et al. (2) as follows: “If the loopperimeter is less than 30 ft (9 m), use three t
34、urns of wire; if theloop perimeter is greater than 30 ft (9 m), use two turns ofwire.” Appendix X1 contains tables showing the inductancevalues for various size loops and shapes (such as rectangular,quadrupole, and circular).5.3 Manpower and the type and amount of installationmaterial and equipment
35、must be determined before the instal-lation is begun. The required materials should be available insufficient quantities to avoid any interruptions in the installa-tion process. Table 1 contains a typical materials list forconstructing an inductive loop detector. Table 2 containstypical equipment ne
36、eded to install inductive loops. Theequipment required for traffic control and installation ofconduit, pull box, controller cabinet, and any equipmentusually placed in the cabinet are not included.5.4 To protect the integrity of the pavement and loopinstallation, cracks and joints in the roadway pav
37、ement shouldnot be located closer than 18 in. (45 cm) upstream ordownstream of the inductive loop detector being installed.Some agencies relax this constraint to 1 ft (0.3m) (5). Saw cutsfor other wire loops or other in-roadway sensors must not belocated closer than 2 ft (0.6 m) upstream or downstre
38、am of theinductive loop detector being installed (6). The distancebetween lead-in saw cuts shall be 6 in. (15 cm) minimum untilthey are within 1 ft (0.3 m) of the edge of the pavement or curb,at which point they may be placed closer together (7). Lead-insaw cuts shall not be closer than 12 in. (30 c
39、m) from adjacentloop edges (6).5.5 After securing the work zone with appropriatebarricades, cones, and so forth to divert traffic from the workarea, mark the pavement to show the size and shape of the loopand lead-in wires to be installed and the required saw cuts.Lumber crayon, chalk, or spray pain
40、t is typically used for thispurpose. If available, a template of the proper size and shapefor the wire loop is recommended. However, a straightedge ora tightened string can be used as a marking guide. It is criticalthat the markings reflect the location shown on the constructionplans.5.6 Cut slots i
41、nto the roadway pavement for the loop wireand lead-in wires using a pavement saw. Do not allow the sawcut in the pavement to deviate by more than 1 in. (25 mm) fromthe markings for the cut (7). The depth of the saw cut shall besufficient to allow at least a 1-in. (25-mm) cover of sealant tobe placed
42、 above the top loop wire or backer rod if such is used(7, 8). Some agencies use 3- and 4-in. (76- and 102-mm) slotdepths for multiple wire-turn loops to prevent future grindingand overlay procedures from destroying the loop (8). Saw cutdepth should be verified at several points during the cuttingpro
43、cess to ensure a constant value. The width of the saw cutshall be sufficient to allow encapsulation of the wires by thesealant. Several methods are available to prevent damage to thewire at the corners of a square or rectangular loop by removingthe 90 angle. In the first method, diagonal cuts are sa
44、wed atthe four corners, allowing a minimum margin of 1 ft (30 cm)from the apparent corner as shown on the left of Fig. 2. WhenTABLE 1 Typical Materials List for 6-ft 6-ft (1.8-m 1.8-m)3-Turn Inductive LoopDescription Quantity/LoopLoop and lead-in wires, such as., IMSA51-3 or 51-5 (3)200 ft (60 m)ALe
45、ad-in cable, e.g., IMSA 50-2 (3) 200 ft (60 m) or moreATape34-in. (20-mm) rubber splicingB1 roll per 6 loopsLoop sealant (per loop) 6 tubes or appropriate number of galloncontainersSealant (per 4 ft (1 m) of lead-in cable) 1 tubeCaulking gun 1Backer rod As requiredCement, sand, or talc 1 bagDuct sea
46、l for conduit 1 blockPull box (sized as required) 1 per splicing locationConcrete As required per pull boxSplice kits 1 per loopSolder As requiredSurge voltage protector As requiredConduit As requiredAQuantity varies according to site requirement, including loop location.BSome states specify a first
47、 layer of PVC tape followed by a layer of rubber tapeor heat shrinkage polyolefin tubing as insulation on the lead-in wire to lead-in cablesplice (4).TABLE 2 Typical Installation Equipment List for Inductive LoopDetectorsItem Description and UsePavement saw Creates saw cut for inserting wires. Typic
48、allya self-propelled 18- to 65-hp saw equippedwith14-to38-in. (6- to 10-mm) thick blade(abrasive or diamond), water valve, depthgauge, and horizontal guideWater supply Cools diamond blade and cleans out sawedslotsJackhammer Bores holes through concrete curbAir compressor Used with jackhammer and to
49、clean and drysawed slotsChisel and hammer Removes sharp edges at corners of sawcutsBlunt tool316-in. to14-in. (5-mm to 6-mm) thick woodpaddle for seating wire in sawed slotWire twisting tool Provides symmetrical twists in the lead-inwiresTemplate/Straightedge Marks outlines of loops on pavementTrenching machine Creates trench for burying cableundergroundVolt-ohm meter andmegohmmeterTests wires for continuity and insulationresistanceInductive loop system analyzer Tests continuity and inductance of inductiveloop detector systemSoldering device Enables solderi
