sentences:  The tolls expressways are, on average, among the most expensive in the world, according to a comparative study realized in 2004 by the Chamber of Deputies.The most traveled freeways are those that link the three most populous cities in Mexico—Mexico City, Guadalajara and Monterrey—in the form of a triangle.No federal freeway or expressway crosses a city; toll expressways are either turned into toll bypasses ("libramientos") often used as toll or free ring roads ("periféricos"), or are transformed into major arterial roads, even if they are, in function, freeways with restricted access.