Trains & wagons

I don't know if it can be done in one pass. Here's a solution with 2 passes through the tunnel:

L moves left to enter circle
L moves counterclockwise to 2 picking up B
L/B continue counterclockwise to 1 picking up A (passes through tunnel)
L/B/A continue counterclockwise entering straight
A is left at 3
L/B move left to enter circle
L/B move clockwise to 1
B is left at 1
L continues clockwise to intersection of circle and straight (passes through tunnel)
L moves right to 3 picking up A
L/A move left to enter circle
L/A move counterclockwise to 2
A is left at 2
L moves clockwise to intersection of circle and straight
L moves right to 3

L enters track then anti clockwise, pushes B (LB) through tunnel collects A (LBA) and leaves A at point 3 (LB) L reverses To leave B at Point 1.

L continues reversing (clockwise) through tunnel past junction and forward to point 3 collects A back out to circle then anti clockwise to leave A at point 2.

Returns to point 3. Mission completed.


Which if I am not mistaken is the way Mark suggested.


I will say it is impossible to do this with only one pass through the tunnel.