Baltimore and Washington. Tutorial advises to lay double track then connect new parallel track to existing track. I do but the tutorial never advances. The single track button just keeps flashing.

I've repeated this section of the tutorial 4 times and can never get past this point. Any ideas?

This is a bit late but it may help someone:

The tutorial does work as I've just completed it, but the instructions are a bit ambiguous.

First to pick up and deliver passengers and mail between Baltimore and Washington, you need to make sure it has both passenger and mail cars on the manifest for both stations. The tutorial would have you believe you only need it in one of them. Normally adding cars to the top station in the list copies it to all the other stations, which you can leave or change as required.

On the track laying, it will depend on the track laying difficulty you have chosen. (I always use the hardest as it is more fun).
The tutorial needs you to connect the end of the doubled track on one side of the Baltimore signal to the single track just on the other side of the signal. The problem comes if the second train has already reached the signal and stuck, as there is very little room to join the tracks in front of the train.. If you can't join it in front of the train, it will remain stuck (and so will you)... so pause the game before the second train gets anywhere near Baltimore station, and join the tracks while paused. Then unpause..
Hope this helps