Signal Loop Installation

1
Signal Loop Installation
Problem Loop damage is a major
cause of signal system failure
Solution Proper installation can
prevent many loop failures
Stop Bar marked
Final lane lines gore marked

• Keys to proper loop installation
• Locate lane lines, crosswalks and wheel chair
  ramps
• Review plans and approve loop locations as marked
  in the field, prior to cutting
• Treat corner cuts in accordance with the plans
• Clean slots with high pressure air and water and
  then dry with air (dont blow into traffic!)
• Perform work in the presence of the Engineer (it
  is critical that some inspection staff be present
• after the cuts are cleaned to measure the depth,
  check the cut and observe loop installation.
• Many failures have been traced back to faulty
  loop installation.)
• After sawing, check depth (Std. 1725.01) and
  remove any jagged edges from within the cut
• Assure that loop wire is not nicked and that it
  is one continuous run/wire from the pull box
• Check to see that the proper number of turns have
  been made
• Test loops Insulation integrity Impedance from
  loop wire to ground gt 100 megg-ohms
• Loop resistance Loop system impedance lt 0.0085
  ohms/meter of loop conductor
• Seal the loop wire using approved sealant.