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Trouble Shooting Loops Dan Inabnitt, CPM Kentucky Transportation Cabinet NATMEC 2004 San Diego, California June 27-30, 2004

Trouble Shooting Loops - Transportation Research …onlinepubs.trb.org/onlinepubs/archive/conferences/NATMEC/2004/15... · Trouble Shooting Loops Dan Inabnitt, CPM Kentucky Transportation

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Page 1: Trouble Shooting Loops - Transportation Research …onlinepubs.trb.org/onlinepubs/archive/conferences/NATMEC/2004/15... · Trouble Shooting Loops Dan Inabnitt, CPM Kentucky Transportation

Trouble Shooting Loops

Dan Inabnitt, CPMKentucky Transportation CabinetNATMEC 2004 San Diego, CaliforniaJune 27-30, 2004

Page 2: Trouble Shooting Loops - Transportation Research …onlinepubs.trb.org/onlinepubs/archive/conferences/NATMEC/2004/15... · Trouble Shooting Loops Dan Inabnitt, CPM Kentucky Transportation

Trouble Shooting LoopsTrouble Shooting Loops

A count is not worth getting injured!In the United States, 120 to 130 workers

die each year in road construction activities.

Of this total, approximately 23% of the fatalities are due to pedestrian workers

being struck by traffic vehicles. Source: The National Work Zone Safety Information Clearinghouse

SAFETY

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Trouble Shooting LoopsTrouble Shooting Loops

OverviewVehicle Detector HandbookSimplified Loop OperationItems to watch forStart with easiest firstRepairReplace Loop

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Trouble Shooting LoopsTrouble Shooting Loops

Moredetailsthanmost couldever use!

Traffic Detector Handbook

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Trouble Shooting LoopsTrouble Shooting Loops

Publication No. FHWA-IP-90-002

http://www.fhwa.dot.gov/tfhrc/safety/pubs/Ip90002/IP90002.pdf

To get the Traffic Detector Handbook

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Trouble Shooting LoopsTrouble Shooting Loops

it’s a wire!inductance is monitoredchange in inductance = detectiondetection = vehiclevehicle = countcount = detector and counter are working!

Simplified loop operation theory

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detector

NO Change in

INDUCTANCE

detector

INDUCTANCE

CHANGEOFF ON

Signal sent to counter

Basic Loop Operation

Page 8: Trouble Shooting Loops - Transportation Research …onlinepubs.trb.org/onlinepubs/archive/conferences/NATMEC/2004/15... · Trouble Shooting Loops Dan Inabnitt, CPM Kentucky Transportation

Trouble Shooting LoopsTrouble Shooting Loops

Source - Traffic Detector Handbook page 107

Typical Loop Schematic

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Trouble Shooting LoopsTrouble Shooting Loops

loop

recorder

lead-in

detector

harness

connection

splices

Usually enclosed cabinet or

above ground j-box

Usuallybelowground

conduit andj-box

In roadway

Usuallyreferred

to as“homerun”.In shoulder and lanes.(twisted)

Terminal stripbutt splices, etc.

Usuallyin conduit(twisted,

shielded & grounded)

Loop Block Diagram

Page 10: Trouble Shooting Loops - Transportation Research …onlinepubs.trb.org/onlinepubs/archive/conferences/NATMEC/2004/15... · Trouble Shooting Loops Dan Inabnitt, CPM Kentucky Transportation

Trouble Shooting LoopsTrouble Shooting Loops

How do I determine if I

have a problem and if I

do, what is the cause

and how do I fix it?

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Trouble Shooting LoopsTrouble Shooting Loops

What to watch for…

Single loopsIs it counting any vehicle?

Is it counting each vehicle?

Is it counting each vehicle only once?Especially watch high bodied trucks

Count several vehicles and match count

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What to watch for…

Double loopsAre they counting each vehicle?

Are they counting each vehicle only once?

Do speeds look reasonable?

Do lengths look reasonable?

Count several vehicles and match count

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Trouble Shooting LoopsTrouble Shooting Loops

Site problems could effect operationRebarOverhead structuresPower LinesAdjacent loops

Try adjusting sensitivity settings

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Trouble Shooting LoopsTrouble Shooting Loops

Components to check...counter

detector

harness/connections

lead-in

splices

loop

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Trouble Shooting LoopsTrouble Shooting Loops

Start with easiest first-

-basic troubleshooting

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Trouble Shooting LoopsTrouble Shooting Loops

Visual Inspection of Roadway

Cracks across saw cuts

Broken wires out of saw slot

Underground utility construction

The milling machine---

(a.k.a - THE LOOPEATER!)

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Trouble Shooting LoopsTrouble Shooting Loops

Counter or Detector?Switch to a working “channel”

Try another known good counter/detector

Double loops

If in pairs, reverse pairing

Separate channels to see if each is counting then

compare totals after a few vehicles to determine if

one is not working correctly

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Trouble Shooting LoopsTrouble Shooting Loops

Use multi-meter to check...continuity

inductance

simple ground test

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Trouble Shooting LoopsTrouble Shooting Loops

Harness and other terminals

disconnect from detector

use pin out adapter

alligator clip adapter

check terminals and splices

replace with known good harness

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Trouble Shooting LoopsTrouble Shooting Loops

Check at Junction box splices

Is there water in splice?

Perform same test as in cabinet

If good at j-box replace lead-in

If bad in j-box, problem is in roadway

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Trouble Shooting LoopsTrouble Shooting Loops

If you can determine that the

loop wire or lead-in is broken and

can find the break,

you may be able to splice it.

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Trouble Shooting LoopsTrouble Shooting Loops

Check Current ConditionsIs it still needed?

Will a non-intrusive technology work?

Check for upcoming construction

Check Inventory RecordsPhoto of site

Specifications

Past inspections

Loop Replacement Before Installation...

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Trouble Shooting LoopsTrouble Shooting Loops

Site Selection

good pavement

nearby structures

overhead power

rebar

new development potential (new businesses, subdivisions, etc.)

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Trouble Shooting LoopsTrouble Shooting Loops

Materials

wiresealantlead-in cablewaterproof splice kitswire numbers

number EVERYTHING! conduitjunction boxes

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Trouble Shooting LoopsTrouble Shooting Loops

Procedure

depth

corners

cleaning

twisted lead-ins

splices

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Trouble Shooting LoopsTrouble Shooting Loops

Numbers will aid future troubleshooting

Waterproof splice kitOff Road Wiring

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Trouble Shooting LoopsTrouble Shooting Loops

It is a lot of work!

Do it right!

and

BE SAFE!

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Summary

Vehicle Detector HandbookSimplified Loop OperationItems to watch forStart with easiest firstRepairReplace Loop

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Thanks!