Control joints are cut into concrete and designed to safely absorb the heat-induced expansion and contraction of the road. They also help absorb vibration, hold parts together, and allow movement due to ground settlement or earthquakes. They are commonly found between sections of buildings, bridges, sidewalks, railway tracks, piping systems, ships, and other structures.
Concrete slabs expand and contract due to warming and cooling from seasonal variation, or due to other heat sources. Before expansion joint gaps were built into these structures, they would crack under the stress induced.
The joints are cut into the structure at regular intervals allow cracking to occur in a controlled fashion. Road control joints can be sealed with hot tar, cold sealant (such as silicone), or compression sealant (such as rubber). #themoreyouknow