Meter Light Standards

[Scott5114]

My primary issue with overhead only ramp meter signals is that they are inconspicuous when the sun is behind them. This is an issue with all signals, but is more apparent with ramp meters as they are typically active only during sun-up and sun-down times.

That depends very highly on the latitude and time of year. In Norman, sunrise today was at 6:15 am and sunset at 8:47 pm, far outside of the normal rush periods. Sunrise and sunset coinciding with peak demand periods really only happens here around the winter solstice.

[jakeroot]

My primary issue with overhead only ramp meter signals is that they are inconspicuous when the sun is behind them. This is an issue with all signals, but is more apparent with ramp meters as they are typically active only during sun-up and sun-down times.

That depends very highly on the latitude and time of year. In Norman, sunrise today was at 6:15 am and sunset at 8:47 pm, far outside of the normal rush periods. Sunrise and sunset coinciding with peak demand periods really only happens here around the winter solstice.

It's not just sunset and sunrise, but also the period leading up to/following it (respectively). The sun can be way up in the sky when you first enter the on-ramp, and then right behind the signal by the time you reach the limit line.

Here in Seattle, morning rush is (guessing here) 5am to 9am, and evening rush from 2pm to 7pm. Sunset and sunrise (and the period leading up to/following it!) are factors basically year-round for at least some drivers.

[Scott5114]

I suppose if the rush is that long, you have a greater chance of sun placement being a problem for at least part of it. Here, evening rush doesn't start until 5pm and is normally cleared out by 6pm.

[jakeroot]

I suppose if the rush is that long, you have a greater chance of sun placement being a problem for at least part of it. Here, evening rush doesn't start until 5pm and is normally cleared out by 6pm.

I shall also imagine that an area with a rush that short likely either doesn't have meters nor need them.

To think peak-hour could be less than an actual hour ... 

[ran4sh]

Sun location doesn't seem to be a problem for most Atlanta ramp meters, which might be why no one here even thinks of it. I-75 and 400 are mostly north/south, and I-85 on the NE side, while it's close to east/west, commuters are generally facing away from the sun. That leaves I-20 on the west side and I-285's east/west sections as the only freeways in the area where this would be a problem during the normal commute.

[mrsman]

Georgia, for a 2-lane onramp, normally installs a mast arm and mounts the ramp meters on there. There are 2 overhead ramp meters for each lane because GA uses staggered release in those situations. Georgia did request an MUTCD interpretation from FHWA regarding the number and positioning of ramp meters for multi-lane onramps with staggered release; they have generally followed that interpretation. https://mutcd.fhwa.dot.gov/resources/interpretations/4_294.htm

https://goo.gl/maps/bgAEm5GX9BNu9i1E6

Has Georgia not heard of a post or pedestal? The best time to use them is at ramp meters, and they still refuse to use them (that MUTCD question indicates some concern about mixing overhead and post-mounted signals ... based on what evidence?). In fact, I cannot recall ever seeing a post-mounted signal in George. Do they even exist anywhere? Apart from DDIs or other offset intersections.

I agree.  I think having 4 separate overhead signal faces as is done in Georgia would be somewhat confusing.  I think the Australian way (as pictured in one of the above comments) is far more intuitive.  One overhead and one side signal face for each lane.  Alternatively, having pedestal only (where both of the pedestals have two signal faces) would be another possibility.  Indeed the FHWA guidance suggests that using pedestals with both a low singal face and a high signal face is common and a good application for staggered release.