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enter image description here enter image description here I thought that ILS holding positions marking are used only on taxiway but this runway seem to have them too.

What is the usecase of using both the standard holding position marking(here yellow with 4 lines) and the intermediate holding position(here red, ladder type) ? Is the red line an ILS sign in this case next to the marking? Cannot find any reference on using the ILS on runways in the FAA specification.

Image details: Runway 4R-22L on O'Haare Chicago Airport. Coordinate: 41.96690186, -87.88337077

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Since the ORD airport runway in question is 22L/4R the "Ladder" type are the ILS critical area hold lines (to prevent interference with the ILS signal) for 28C and 28R (it's hard to determine because of the photo). The regular hold lines (4 yellow lines - 2 solid and 2 dashed) are to protect approaches for 28R so aircraft landing on that runway (28R) do not pass above an aircraft that has landed on 4R and is rolling out underneath its approach path (Land and Hold Short for the aircraft landing on 4R).

The aircraft landing/rolling out on rwy 4R would need to hold short at the hold lines to protect the aircraft landing on 28R, as instructed by the Tower.

Depending on an airport's runway and taxiway configuration having both Holding Position Markings on a runway and ILS Critical Area holding points on a runway is not uncommon.

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  • $\begingroup$ Thanks for your detailed answer. So,if i understood right the missing yellow lines(not ladder) on 4R-22L, other then the one in fron of 28R is because the 28R is the closest to the 22L-4R runway, so there is no need to have on the imaginary intersection with 28L or 28C. Also, what is the reason of having the first ILS ladder marking on 4R if for landing(from south) the pilor cannot anyway stop in front of 28L(because too short for landing otherwise) ? $\endgroup$
    – Alexis
    Jul 11 at 12:18
  • $\begingroup$ It's possible, although, I don't know for sure, that the first hold lines (rwy 4) are positioned for 28R and absent for 28L/C is because rwy (4R) only supports land-hold-short operations to accommodate 28R. Simultaneous ops on rwy 4R and 28L/C wouldn't be conducted (I guess). I suspect the first ladder on 4R is for any taxiing aircraft or vehicles (not just landing aircraft) on the approach end of 4R to protect the ILS signal for 28L. That would be my guess because all the ILS Critical Areas need to be protected. $\endgroup$
    – 757toga
    Jul 11 at 14:17
  • $\begingroup$ I think it is also important to note that all over the ORD airport there are many ILS critical area hold points (ladder markings). Any location, runway or taxiway, where a vehicle or aircraft could interfere with an ILS signal you will see an ILS critical area hold point. So, the fact that they are not just painted on taxiways is understandable. Also, I don't see the white on red "ILS" signs (on the pavement) for any of the ILS critical area hold points. ORD has a complex taxi and runway configuration and locating these points is important anywhere on the airport where needed. $\endgroup$
    – 757toga
    Jul 13 at 17:22

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