Emergency vehicle lighting refers to any of several visual warning evices, which may be known as light bars or beacons, fitted to a vehicle and used when the driver wishes to convey to other road users the urgency of their journey, to provide additional warning of a hazard when stationary, or in the case of law enforcement as a means of signaling the driver to stop for interaction with an officer. They are often used along with sirens in order to maximize their effectiveness. In many jurisdictions, the use of these lights may afford the user specific legal powers, and may place requirements on other road users to behave differently, such as compelling them to pull to the side of the road and yield right of way.