Before approaching the tunnel, another walker warned that the tunnel had a large number of active bats. That was an understatement!!!
The bats were swarming with more vengeance than bees on a mission, and not afraid to fly within millimetres of anyone adventuring into the tunnel.
According to Wikipidea: The Oakey–Cooyar railway line was a branch line in the Darling Downs region of Queensland, Australia. The small town of Cooyar is about halfway to Kingaroy in the South Burnett region. A plan to connect Kingaroy to the south via Cooyar did not eventuate and left Cooyar at the terminus of a branch line running from Oakey west of Toowoomba. It was opened on 28 April 1913 after previous stages to Kulpi and Peranga opened on 29 April 1912 and 4 November 1912 respectively. The line was partially closed beyond Acland on 1 May 1964, with the last segment closed on 8 December 1969.
Mixed trains initially ran four times a week and were replaced in 1929 by a daily rail motor service to Toowoomba. The line connected the small towns of Acland, Kulpi, Peranga, Narko, Nutgrove,Wutul and Cooyar to the Queensland Rail western line at Oakey until 1964. This provided passenger and farm produce services not only to these towns but also to the surrounding townships of Quinalow, Maclagan and Evergreen.
Coal was transported between Acland and Oakey, this portion of the branch line remained in service until 1969. A similar parallel branch line existed connected Haden to the Western Line at Kingsthorpe from 1910 to 1964. As the competing service of bullock carts gave way to motor vehicles rail patronage declined resulting in both services becoming uneconomical to maintain.
With negligible track remaining the Oakey-Cooyar branch line could all but be overlooked as a fading scar on the landscape, it retains its significance however through the still intact Muntapa Tunnel. A feat of early Queensland Railways engineering achievement, the Muntapa Tunnel remains the only tunnel in Queensland to pass under the summit of Eastern Australia's Great Dividing Range. This tunnel was constructed with manual labour. It is now home to a colony of bats.
The Oakey-Cooyer branch line is also of early surveying significance. Rail engineering practice of the period avoided the construction of tunnels, so significant surveying was undertaken to avoid tunnelling and to minimise rail gradients. The largest gradient of a line mandates a larger, more expensive loco or a de-rating of carrying capacity, both of which would result in a less economical service for the line as a whole. The Oakey-Cooyar branch line was repeatedly surveyed to arrive at its built route, which had a negligible gradient over its length, but which required the 300m tunnel. The low gradient required a devious route, particularly at Narko and adjacent to the tunnel.
- The Cooyar Branch Line Milne, Rod Australian Railway Historical Society Bulletin, July, 1996 pp195-205
- "Muntapa Tunnel - Trail Description". Retrieved 2008-09-14.
- "Entry CHIMS22212". Queensland Heritage Register. Queensland Environmental Protection Agency. Retrieved 2008-09-14.
- Queensland Historical Legal Collection
"Triumph of Narrow Gauge: A History of Queensland Railways" by John Kerr 1990 Boolarong Press, Brisbane