I don't work the traffic and signals market...
But the last NEC/ IBEW job I saw used bare #10 solid as the grounding conductor inside PVC for street illumination. It appeared that they used 1 1/4" as their minimum conduit size.
I was kind of jealous, they had an entire 20-foot double axle trailer dedicated to holding their conductor selections. I could never get such a rig to roll around our big box slabs.
That's the only contractor I can recall using bare grounding conductors -- excluding bare solid grounding electrode conductors.
