Generally, the distance that is calculated for these signs is not the distance to the border or city limits, but rather to the estimated center of a city. They also are not calculated by a straight-line from the sign to the city, but instead the distance along the ideally-quickest route to take, taking into account all the turns and curves drivers will take, and the distance may not be perfect. For example,
U.S. Route 50, a cross-country route, has a sign in
Sacramento, California, stating that
Ocean City, Maryland, its eastern endpoint, was away, whereas a sign in Ocean City once said that Sacramento was away. In some countries,
route numbers may also be displayed above or alongside the listed destinations, thereby taking on the additional role of
reassurance markers. The frequency of mileage signs do differ between
rural/countryside areas,
cities, and
the suburbs. They are much more common in the countryside compared to cities because most drivers simply pass through these regions on a major highway to get to their destination, letting them know how far they are from the nearest major town, village, or city. In contrast, highways in or near urban cities will list locations or junctions with other highways as
control cities instead, which differ from mileage signs because they are posted only at
gores or exits (or upcoming exits), and do not give the distance to them. Mileage signs may be seen exiting a city, but typically are not used inside or entering a control city. ==Europe==