Train lighting really helps bring night scenes alive. But hiding a couple of batteries plus power switch in every carriage is a pain, not to mention having to charge or replace the batteries.
So for my open carriage I invented a better system.
Since my Red Monster has a 5v regulator on board, I made use of this and mounted an external jack next to the coupling providing access to this. The actual jack can be seen in the first photo above and is part of an el cheapo IC socket that's been chopped up.
The actual hoses are made from 2x PCB pin headers, soldered to black shielded audio cable at each end, with heat shrink applied over the soldered bits, like in the second photo. The trick is to make them the right length, and with the smallest possible length heatshrinked.
If you've done it right, it should look like a train brake hose. The actual lights can be pinched from xmas tree lights. At $15 for 250 lights from our local discount store you can't really complain!