What are these devices on or adjacent to an airport taxi-way?
It is not a road that you are looking at, it is the edge of the runway / taxiway.

The double yellow lines are used to define the taxiway
edge from the shoulder or some other abutting paved
surface not intended for use by aircraft.

The blue lights in the yellow boxes are taxiway edge lights.

The poles next to the lights are blue reflective markers that will mark the taxiway in case the light fails. Systems for light control often work for groups of lights (e.g. sections of taxiways) or, if individually controlled, through a control signal on the power line powering the light. In the latter case, there is a small piece of electronics in each light housing controlling the intensity of that individual light and reporting back if the light fails.

The yellow objects in the blue boxes are signs. They indicate names of taxiways, runways, holding points etc. You see the backside of light casings, not the signs themselves. A bit further to the right you can see similar signs. 

I am not sure what the item in the red box is.