Drones are to be used by Dorset, and Devon and Cornwall police to aid in matters including missing people searches and crime scene photography.
The six-month trial has begun in Devon and Cornwall, and is due to start in Dorset on 26 November.
The drones are equipped with high definition cameras which can capture video and still images.
The forces said they were not a replacement for the National Police Air Service (NPAS) helicopter service.
Two drones are being used by officers in Devon and Cornwall, and two will be used in Dorset.
Insp Andy Hamilton, who is leading the trials, said: “Drones offer many benefits that complement the NPAS helicopter and are by no means a replacement for this service.
“This technology offers a potentially highly cost effective approach to missing person searches, crime scene photography, and responding to major road traffic collisions.”
He added drones enabled officers to capture footage on “difficult terrain”, including cliffs and woodland, enabling them to “respond effectively at the scene”.
“This technology still has its limitations; the models we are trialling are currently unable to fly at night or in adverse weather, but having the option to put a drone in the air in a few minutes’ notice could help save lives,” he said.