We should also be comparing more than one distance, as the fare charged would also depend on the fare structure. For instance:
City A has a distance-based fare structure charging at the rate of $3.50/km,
City B has a zone-based structure similar to Melbourne's, charging $5.50 for a single zone, and $12.50 for two zones, with each zone having a radius of 20km,
City C also has a zone-based structure, but with a zone radius of 10km, charging $7.50 for a single zone, and $15.00 for two zones.
Say we pick 3 distances: 5km, 10km, and 15km.
Fares in City A would be as follows: $17.50, $35.00, and $52.50 respectively,
Fares in City B: $5.50, $5.50, $5.50, as all distances are within the one zone,
Fares in City C: $7.50, $7.50, and $15.00.
Thus, City A would have the cheapest fare for travelling less than 2km, but City B would have the cheapest fare for travelling 5km or more.