When Major Thomas Mitchell was appointed as Surveyor-General in 1828, one of the first matters to which he turned his attention was the improvement of the Great Western Road. Mitchell's attention was focussed on providing a more direct and easily graded route for the Great Western Road. To this end, he surveyed a route running northwest from Hartley via Mt Walker to Meadow Flat, crossing the Great Dividing Range at Mount Lambie, then running in an almost straight line westward via Browns Hill to Kelso, to meet the pre-existing road. This road remains in existence - from Mount Lambie west it remains as the route of the current Highway (with deviations) but the section adjacent to Cox's River was inundated by the construction of Lake Lyell for Wallerawang Power Station in the late 1970s.