Similar to the RSA sign above, this symbology also is located on the back side of a sign; in this case, the ILS critical area
The ILS critical area hold lines are two, yellow solid lines spaced two feet apart, connected by pairs of solid lines spaced 10 feet apart extending across the width of the taxiway.
You could be on a coupled approach with a reported ceiling of 900 feet, and at 1200 feet AGL experience distortions as a Citation Jet taxies up to the hold-short line through an unprotected ILS critical area.
A pilot can request that ATC protect the ILS critical area (although I wouldn't try it at O'Hare).
If you're taxiing out at an airport that's uncontrolled (due to a closed tower or otherwise) and you notice an ILS critical area, pause and think before you taxi past.
AIRPORT SIGN SYSTEMS TYPE OF SIGN AND ACTION OR PURPOSE [4-22] Taxiway/Runway Hold Position: Hold short of runway on taxiway [26-8] Runway/Runway Hold Position: Hold short of intersecting taxiway [8-APCH] Runway/Runway Hold Position: Hold short of aircraft on approach [ILS] ILS Critical Area
Hold Position: Hold short of ILS approach critical area [?
Unmonitored" and the construction equipment being in the ILS critical area
(we're guessing) had nothing to do with each other.
Because other aircraft or vehicles can skew the signal, ground control may ask you to observe the ILS critical area
hold short lines when the weather is lower than 800 feet and two miles or 200 feet and RVR 2000 (when an inbound is inside the MM).
For this reason, ILS Critical Areas
are established and when weather is below 800-2, towers keep these areas clear.
Lacking an ILS beam, there will be no ILS critical areas