How are curbs measured?

A curb is the edge where a raised sidewalk or road median meets a street or other roadway. Curb indicates the boundary between the pavement and shoulder; or sometimes islands or footpath or curb parking spacing. It is desirable to provide curbs on urban roads. 

By raising the edge of the pavement, curbs separate the road from the border of pavement, thereby discourage drivers from parking or driving on sidewalk.Curbs are also used to channel runoff water from rain into storm drains.