Heres an interesting challenge for you.
Recently, down Brissie way, I was told of a proposed railway underpass under the Bruce Highway between Pine River and Bribie turn off. Apparently, it was built when the new double highway was put through, just in case, sometime in the future, the Govt was going to put a railway line to Redcliffe. Heres how to find it.
Heading north along the freeway, look for the BOUNDARY RD off ramp. Go under the overpass, and about 3-400 metres past the overpass, look for the brown sign facing the traffic coming from the north that announces the BOUNDARY RD exit. Directly under this sign, going right through from one side to the other is the underpass. You can get off the road there, theres a few tracks through the scrub, and you can get to the underpass. Its pretty awesome.
Try going through from west to east, but be careful, cause on the east side is a monster hole, (when I was there, it was about 3 ft deep with water) with a near verticle about 6 ft climb up out of the hole. 
Anyone else know of this, or seen it?? Obviously, 4wders from round the area know of it, cause theyres heaps of tracks through the bush.
If ya find it, let me know what ya think, and if ya manage to get through.
Next time im down there, im gonna attempt it with double diff locks, the single in the rear couldnt get me through.
Have fun
David
