Same here. Maybe the green is just on more often, or the lifespans are shorter. I'd imagine that at an intersection with an inductor coil and where one road is much busier than the other then the green would be on most of the day, likewise with the red on the perpendicular road. Perhaps it has gone unnoticed because it is less likely for one of us to travel one of those roads. It might be worth a trip down the less-driven perpendicular road to see if the same is true of the reds. I suppose the yellow would last the longest in most cases.
Another is that the green LEDs are likely less efficient than the other colors. Particularly for older fixtures that are several years old, green LED efficiency was quite low back in those days, so my guess is they might be driven harder than the reds in general. Very very few engineers I know are aware of how sensitive LEDs are to overdrive, that is, how expected life of LEDs (particularly epoxied 5mm LEDs) drops so severely due to increasing the current.
If I were designing street light assemblies though, I would want to overengineer the fixture assuming a worst case scenario: make the fixture robust enough to survive a 100% ON duty cycle, with record high ambient temp and humidity, and dirty mains power supply. Also use circuit boards aimed at surviving wide temperature swings -- Many of the failure modes I've seen in some of the oldest LED traffic lights (at least 10 years old) are single strips of flickering off an on, which wuold suggest a broken wire or trace on the circuit board, probably from thermal expansion/contraction over the years, causing a break on the circuit board.
For one, most of those fixtures have relatively few 5mm LEDs spread pretty far apart. They have room to fit more than 10x as many LEDs on the surface if they wanted to. IMO a reasonable approach would be to use 4x more LEDs in the same surface area, and drive them at maybe ~20% of the current as before, and get the same overall brightness with substantially less heat. 5mm LEDs are not that expensive, the extra unit price of those 5mm LEDs and circuitry would likely be less than the cost of the labor to replace something like traffic lights even once. Not to mention reliability/safety.
