Left turn signal

Are you sure it isn't a yellow and green fiber optic or LED arrow? If so, it is acceptable. If it is a green-only arrow, It would only be workable if it is followed by a yellow ball, then red ball. I say "workable," not "acceptable" because I suspect it isn't allowed in the MUTCD. You could pose this question on the MUTCD Q&A forum, .

The "doghouse" five section head is preferred by people with a certain (fairly rare, IIRC) type of color blindness, since it makes it easier to tell the difference between yellow and green arrows by location.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

I'm sure its not a dual color arrow. The signal is very old. I think it would be best to replace with the 5 section.

The MUTCD specifically depicts the four-lens layout in Figure 4D-3, G. As AC said, this would only be acceptable if the green ball/arrow were followed by a yellow ball. If used as a leading green, a yellow arrow section is required.

what is the difference between those two signal heads (other than the layout of course)?

Is the second layout used for lead/lag left greens, while the first ("doghouse") used for 8 phase signals?

In Maryland, both types of signal heads may be used at the same intersection. The 4-section may be used as a near-side signal head (both ground or overhead) or as a ground-level supplemental far-side signal head. The 5-section will be used as the overhead far-side and may also be used as an overhead near-side, though I cannot recall seeing it as a ground-mount near-side.