[charlieboardman]

To expand on the angles of a polygon idea. It looks like each of these tracks has about a 30 degree bend. So you should have 360/30 = 12 more right-handed than left-handed tracks, or vice versa. It takes some counting, but you could probably get pretty quick at going around the track and adding or subtracting 1. If you end at 12, perfect. Your distance from 12 is an estimator for tension.

[CrazyStat]

This is necessary but not sufficient for there to be no tension. For example, if you have 12 curved pieces, all curving in the same direction, and one straight piece, there will be tension.