TRAFFIC MONITORING DETECTOR LOOP
PART 1 GENERAL
1.1SECTION INCLUDES
A.Test detector loop and detector cable.
1.2RELATED SECTIONS
A.Section 13553: ITS Conduit
B.Section 13554: Underground Junction Box
C.Section 13555: ITS Cabinet
D.Section 13595: ITS Integration, Inspection, Testing, and Acceptance
1.3REFERENCES
A.ASTM D 3005: Low-Temperature Resistant Vinyl Chloride Plastic
Pressure-Sensitive Electrical Insulating Tape
B.International Municipal Signal Association (IMSA)
C.National Electrical Code (NEC)
D.RUS Bulletin 17551-100
E.Underwriters Laboratories (UL)
1.4DEFINITIONS Not Used
1.5SUBMITTALS
A.Manufacturer’s parts list, wiring schematics, installation instructions, shop
drawings, and maintenance manuals for review.
B.Certified test report of detector homerun cable compliance. Refer to IMSA
50-2.
1.Submit before beginning 30 Day Burn-in Test.
Traffic Monitoring Detector Loop
C.Warranty letter for information stating that the contractor guarantees the
traffic monitoring loop against all material defects for a period of 15 years.
1.The guarantee periods start on the date of substantial completion.
2.Include in the letter:
a.State Project Designation
b.State Project Name
c.Contractor, Provider, and Installer Name
3.The guarantee covers 100 percent of the traffic monitoring loop
materials and installation costs.
PART 2 PRODUCTS
2.1MATERIALS
A.Use electrical components as listed and defined by the NEC.
2.2WIRE
A.Detector Homerun Cable.
1.2 Conductor No. 12 shielded polyethylene insulated. Refer to IMSA
50-2.
B.Detector Loop Wire.
1.PVC Sensor Loop Wire – No. 14, single-conductor, stranded wire.
Refer to IMSA 51-3.
C.Commercially Manufactured Preformed Loop.
1.Abrasion-resistant alloy cover with braided synthetic fiber
reinforcement.
2.Withstand minimum pressure of 1,400 psi.
3.Flexibility over a wide temperature range and rated to withstand the
temperatures of an asphalt overlay project.
4.Resistance to oil, gasoline, salt, moisture, and impact.
5.Loops individually marked showing the direction of the wire turns.
6.Include an additional turn in loops that are more than 8 inches
below finished surface to compensate for reduced sensitivity.
D.Splice Sealing – Refer to Rural Utilities Service (RUS) Bulletin 17551-100.
1.Insulate conductors individually and encapsulate with mastic rubber
pads and over wrap with vinyl electric tape.
a.Overcoat completed splice with waterproof sealant. Refer to
ASTM D 3005, Type I or II.
b.Refer to UL 510.
Traffic Monitoring Detector Loop
PART 3 EXECUTION
3.1PREPARATION
A.The number of preformed loops and the number of lanes varies based on
location shown.
3.2INSTALL PREFORMED DETECTOR LOOPS
A.Refer to AT Series Standard Drawings.
B.Preformed Loop
1.Place loops under new pavement 1¾ inches below the surface of
the base course and backfill with surrounding material.
C.Seal loop wire ends immediately upon installation with waterproof coating,
coil neatly, and place in a junction box.
D.Conduit Connection to Junction Box
1.Seal conduit with waterproof bushings. Refer to Section 13553.
2.Fill voids resulting from conduit entrance into junction box with
hydraulic cement grout. Refer to Section 13554.
3.3LOOP WIRE AND LEAD-IN CABLE INSTALLATION
A.Loop Detection Wire Splicing
1.Splice only in junction box.
2.Splice cables only in detection circuits where the wire type changes
in the junction boxes.
a.No other splices are allowed.
b.Use a nylon tie wrap to secure the loop leads at the best
location possible inside the junction box.
c.Provide loop leads that are at least 36 inches long as
measured from the top of the junction box to allow the Contractor to work on the splice above the box.
d.Carry the shield over the splice.
B.Install detector homerun cable from loop wire to cabinet.
1.Refer to Section 13555.
2.Connect homerun cable to input file in cabinet to make loop
detection fully functional at cabinet controller location.
3.Install cabling neat and tight within the ITS cabinet.
Traffic Monitoring Detector Loop
C.Install detector wiring and color code cables according to Table 1 and AT
Series Standard Drawings. Identify each home run cable in every junction box.
1.Use electrical tape and color-code the home run cables using the
following color and number scheme:
a.1 = Brown
b.2 = Red
c.3 = Orange
d.4 = Yellow
2.Place the colored bands at the end of a home run cable. Use Table
1 to select the proper color band.
a.Place the first colored tape band to indicate the lane. Lane 1
is nearest to the traveled lanes.
b.Place the second colored tape band to indicate the zone
where loops are located. (Passage, Demand, Mid Queue and Advance Queue.)
c.Place the third colored tape band to indicate the first or
second demand loop in the pair.
d.The demand loop closest to the stop bar is Brown, the next
demand loop in the pair is Red.
Table 1 Color Coding to Identify Home Run Cables Zones and Loops Lane 1 = Brown Lane 2 = Red Lane 3 = Orange Lane 4 = Yellow
Passage Loop Loop 1 (Br-Br) Loop 5 (Red-Br) Loop 9 (Or-Br) Loop 13 (Ye-Br) Demand Loop Front Loop 2 (Br-Red- Loop 6 (Red-Red- Loop 10 (Or-Red- Loop 14 (Ye-Red- Br) Br) Br) Br) Demand Loop Rear Loop 2 (Br-Red- Loop 6 (Red-Red- Loop 10 (Or-Red- Loop 14 (Ye-Red- Red) Red) Red) Red) Mid Queue Loop Loop 3 (Br-Or) Loop 7 (Red-Or) Loop 11 (Or-Or) Loop 15 (Ye-Or) Advance Queue Loop Loop 4( Br-Ye) Loop 8 (Red-Ye) Loop 12 (Or-Ye) Loop 16 (Ye-Ye)
3.4ITS INTEGRATION, INSPECTION, TESTING, AND ACCEPTANCE
A.Follow the integration, inspection, testing, and acceptance process
according to Section 13595 with the following exceptions:
1.Perform LFOT testing after all TMD loop elements, equipment and
hardware, power supply, and connecting cabling have been installed.
a.It is not necessary for the communications installation to be
completed at the time of testing.
b.It is not necessary for all stations to be tested concurrently.
Traffic Monitoring Detector Loop
B.Detector Loop Circuit – Conduct the following acceptance tests before and
after backfill for approval by the Engineer.
1.Measure and report in ohms, the continuity of each loop.
2.Value to be within 5 percent of calculated values.
3.Loop Resistance Formula Rt = Rl + Rd.
Where: Rt= Resistance of loop as measured at junction box. Rl= Resistance of loop lead in wire (from the loop to junction box). Equal to 0.002525 ohms per foot (times 2) measured from loop to junction box splice point. Rd = Resistance of Loop = PTRc (See Loop Resistance Table below). P= Perimeter of loop in feet. T= Number of turns in the loop. Rc= Resistance of #14 AWG copper wire per foot equals 0.002525 ohms.
Table 2 Loop Resistance Loop Type Rd Loop Resistance Width (ft) Length (ft) Turns (ohms) 5 6 4 0.22 5 10 4 0.32 6 Circular 4 0.19 6 Circular 5 0.24 6 6 4 0.24 6 10 4 0.32 6 12 4 0.36 6 14 3 0.30 6 16 3 0.33
4.Measure and report each loop’s insulation resistance.
a.Minimum acceptable reading measured between the loop
conductor and ground is 50 MΩ or greater when tested with a 500 V megohm meter.
5.Measure and report the inductance of each loop.
a.Acceptable inductance readings are greater than 90 µH for
individual loops and less than 1,000 μH for a 4 loop group.
END OF SECTION Traffic Monitoring Detector Loop
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Source: Utah Standard Specifications for Road and Bridge Construction, 2026 Edition. Pages 1260–1264 of 1,331.
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