Video cameras attached to officers' uniforms are to be worn by a police force after a trial was deemed a success.
West Yorkshire Police are to phase in the cameras for all officers after a pilot scheme in Bradford.
The devices film while officers are out on duty and could be used to gather evidence for court cases.
Assistant Chief Constable Andy Battle said the £2m project would have "significant and tangible benefits".
The body-worn cameras are switched on by the officer when needed. The cameras are not on all the time.
Images are to be stored for 30 days and then deleted if not needed as evidence, said police.
ACC Battle said the cameras would improve the integrity and corroboration of evidence by acting as an "independent witness".
The cameras had also led to an increase in early guilty pleas, he said.
"When officers have worn the cameras, there is also evidence that people's behaviour has changed when they know they are being filmed and that incidents are resolved more effectively", he added.