The purpose of isolation and expansion joints is to prevent damage from differential movements.

Although the terms are sometimes used interchangeably, isolation and expansion joints serve different purposes. Isolation joints separate the pavement from an adjacent structure, another paved area, or an immovable object. Expansion joints are located at regular intervals along the pavement to relieve compressive stresses that may develop in very hot weather.

Good design and construction of contraction joints have virtually eliminated the need for pavement expansion joints, except under special conditions. Eliminating unnecessary expansion joints can minimize pavement failures, reduce construction and maintenance costs, and improve pavement performance.