If used, barrier reflectors should be placed in one of the following locations:

In the depressed center section of a W-beam guardrail (butterfly type retroreflective device, see Figure 8-14),
On top or on the side of concrete barrier (see Figure 8-14), or
On guardrail/bridge rail posts or blockouts.

Barrier reflectors should be installed a minimum of 18 inches above the edge of the pavement surface. Consistent barrier reflector height along the barrier is desired.