Could the FHWA rescind interim approval for bimodal green arrow/FYA heads?

[Pink Jazz]

Last year, there was a study by TRB/NCHRP about bimodal green arrow/flashing yellow arrow heads, and apparently the recommendation was against them.  Instead, TRB/NCHRP recommends placing the FYA in the same position as the steady yellow arrow, which the FHWA granted interim approval last year in three-section signals (not in doghouses).

Based on the study by the TRB/NCHRP, could the FHWA rescind its interim approval for bimodal green arrow/FYA heads?  Since the FHWA granted interim approval for placing the FYA in the steady yellow arrow position, that pretty much solves the issue of height restrictions (or installation limitations such as the "modular" traffic masts that I mentioned in another thread, which only allow for three heads vertically), and TRB/NCHRP recommends them over bimodal green arrow/FYA heads.

[roadfro]

The bimodal green/flashing yellow arrow version of PPLT displays doesn't have interim approval...it's in the MUTCD. To remove that option would require a revision to the MUTCD.

Can you link to the study? I don't recall hearing a recommendation against the bimodal arrow...I think the original study that went into approving the FYA in the first place carried the bimodal arrow as an acceptable option.

(For the record, I don't like the interim approval allowing the FYA to be displayed in the steady yellow section. I think having the visual "jump" of the yellow arrow between sections is beneficial. I'd guess this was brought about by some agencies not wanting to spend extra money for a bimodal arrow.)

[Pink Jazz]

The bimodal green/flashing yellow arrow version of PPLT displays doesn't have interim approval...it's in the MUTCD. To remove that option would require a revision to the MUTCD.

Can you link to the study? I don't recall hearing a recommendation against the bimodal arrow...I think the original study that went into approving the FYA in the first place carried the bimodal arrow as an acceptable option.

(For the record, I don't like the interim approval allowing the FYA to be displayed in the steady yellow section. I think having the visual "jump" of the yellow arrow between sections is beneficial. I'd guess this was brought about by some agencies not wanting to spend extra money for a bimodal arrow.)

Here is the study:
http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w207.pdf

[jakeroot]

I think having the visual "jump" of the yellow arrow between sections is beneficial.

Canada disagrees with you.

[vtk]

I didn't know bimodal arrow was an acceptable option, and I don't like it because color deficiency – though I recognize blinking disambiguates the situation if the driver knows correctly what combinations of color, ball vs arrow, and steady vs blinking, exist.

[Pink Jazz]

I didn't know bimodal arrow was an acceptable option, and I don't like it because color deficiency — though I recognize blinking disambiguates the situation if the driver knows correctly what combinations of color, ball vs arrow, and steady vs blinking, exist.

A red-green colorblind person from Mexico might have an issue, because in Mexico a flashing green light or arrow means the green phase is about to end, and people who are red-green colorblind can't distinguish colors ranging from red to green (green and yellow would look too similar).

I know in the older incandescent signals, the red light contained a slight amount of orange, and the green light contained a slight amount of blue.  However, is that still the case with LED signals?  The light output of LEDs are typically monochromatic as far as I know.