on the rails

To The wineplace.com and Chris, Marshy and Chris for keeping me on the rails.

For several Saturdays after he'd seen a film about men who lived on the rails, he left home with a Spam sandwich in a paper bag, a compass and a ball of twine (though he wasn't sure why he included the twine).

The larger the wheels, the less will any dust, twigs, or inequalities on the rails affect them.