 On July 21 , 1989 , OTA approved a contract to transplant approximately 290 live trees in the path of the turnpike to locations along the edge of the right @-@ of @-@ way . There , the trees would serve as a barrier between the road and the surrounding properties , masking the road from view and muffling the sounds of traffic . A Norman landscaping firm performed the work , which included thirty months of maintenance , for a total cost of $ 288 @.@ 50 per tree ( $ 544 @.@ 19 in 2013 dollars ) . 
