Here in Ohio it is required...

Lawriter - ORC - 2923.126 Duties of licensed individual.
Duties of licensed individual
If a licensee is the driver or an occupant of a motor vehicle that is stopped as the result of a traffic stop or a stop for another law enforcement purpose and if the licensee is transporting or has a loaded handgun in the motor vehicle at that time, the licensee shall promptly inform any law enforcement officer who approaches the vehicle while stopped that the licensee has been issued a license or temporary emergency license to carry a concealed handgun and that the licensee currently possesses or has a loaded handgun.