Reinforced PMMA acoustic sound barriers can be made from Plazit-Polygal's Plazcast SMR sheets which contain metal rods for maximum strength. 

This not only means that they withstand impact without collapsing, but the metal framework holds the plastic pieces together safely. They can be found along many major highways around the world, where they protect adjoining neighborhoods from noise disturbance and protect drivers from flying debris when accidents occur in the other lane.