Small businesses and families of schoolkids are pleading for government assistance as a pivotal highway is set to be closed for months. The 194-year-old convict-built Mitchell's Causeway, a key link in the main highway connecting Sydney to western NSW, will be closed for at least three months for urgent repairs. The Blue Mountains causeway was closed on Sunday, March 8, after significant cracking and movement were detected in the road's substructure.