The series of marks upon one's arm due to injection of heroin. When the marks run up and down someones arm, similar to the tracks of a train, they are said to have train tracks.
Watch out for Paul man, he's totally addicted. Train tracks all over his arm.
By Anthea
Train Tracks
when two bowls of marijuana are passed in opposite directions in a circle... and when the two bowls meet, the person has to train track them by hitting two pipes at once.
People with braces that has theirs lined up it looks like a train could run on it. Legend says you can hear 'Thomas the Tank Engine' theme song if you go near them. But it'll be hard to get close to them as they are very insecure.