What is Track width?

Is it the width from the outside of one tire to the outside of the opposite tire?

OR

Is it the width from the center of one tire to the center of the opposite tire?

In french, we use the word "voie", and it means the width from the center of one tire to the center of the opposite tire.

 

No idea?

 

Usually measured from the center point of the tires - that way it negates tire size and profile discrepencies between manufacturers.