Gimbal lock

I am creating a game in which a vehicle moves forward within a closed cylindrical tunnel which has lots of turns and also has splits which splits into 2 tunnels . The movement of my vehicle is such that all the faces of the tunnel (hexagonal tunnel, so 6 faces) is kept as the vehicles base, no gravity as such. My vehicle doesn't turn left or right but swings towards left or right. So, in a straight tunnel my vehicle moves just fine, but when the tunnel splits into two that's where the gimbal...

Gimbal lock