what are the blue reflectors for in the roadway?

also it may identify going the wrong way up an exit ramp for expressways and freeways, depending in what state you live in, oregon, has them up next to red warning signs for wrong way drivers on freeway ramps.

IDENTIFIES A FIRE HYDRANT, If you look to the left or right when you see the blue reflector in the middle of the street. You will see a Hydrant, they are put there for the Fire Department to quickly locate a hydrant after dark.

In AZ, they indicate where fire hydrants are located.