Sentence:  Diesel is available at roughly 300km intervals on the WA side, as is <WSD>Opal</WSD> fuel which, at the Warburton and Warakuna roadhouses, can be used instead of unleaded petrol. (<WSD>Opal</WSD> is unsniffable, and its provision is one of the measures in place to counteract petrol-sniffing problems in local communities.) 
Meaning of the word marked with <WSD> tags:  A type of petrol made by (British Petroleum) designed to be unable to be used for petrol sniffing.<ref>[http://www.bp.com/sectiongenericarticle.do?categoryId=9008933&contentId=7016884 BP article on Opal].</ref>(Developed 2005.)