- Outline the edges of pavement as an easily definable borders 

 - Confine pavement structures

 - Keep low speed traffic within the edges of pavements

Curbs may have an apron or gutter section attached, thus being referred to as curb & gutter.  You will find these combinations along streets or parking lots.  They may be combined with asphalt pavement.  The concrete curbs & gutters provide stability and flow lines for water to follow curb lines away from pavement.

There are two types of concrete curbs: barrier or mountable.  Curbs are constructed depending upon the purpose.  Barrier curbs are also referred to as stratight curbs, for they resemble stone slabs used for ancient curbing.  These curbs keep vehicles from leaving the pavement. Mountable curbs, also known as roll curbs, have sloping sides that allow vehicles to encroach on them without damaging tires.

Curbs must meet city or county requirements so they provide long service.  They must have mass, stability and strength to withstand traffic and environmental impact.  Curbs are jointed or reinforced to accomodate for temperature fluctations that cause them to shrink. Curbs will crack if they experience too much change in temperature or moisture changes. However good joints that are placed at proper intervals will reduce wear.  Joints are typcially spaced about 15 feet apart. 

There are standards for curbing published by the American Association of State Highway and Transportation Officials (AASHTO).