 The sealing of North West Coastal Highway was nearing completion in 1973 ; additional resources provided to complete the work resulted in the final section , Port Hedland to Roeburn , being finished in only five months . An official opening ceremony was held at South Hedland on 6 December 1974 , with the road pronounced open by Premier Charles Court . The final cost of the project was approximately $ 31 million , substantially more than the initial estimate of $ 17 million . This was mainly due to two factors : increased construction standards , and inflation , which rose from 4 % to 13 % between 1970 and 1974 . 
