Mental health units to be set up by Dyfed-Powys Police
People who have suffered mental trauma after being involved in police incidents will be looked after in mobile units instead of cells in the Dyfed-Powys area in future.
The force said it occasionally had no choice but to hold such people in custody until treatment could can be provided, at rate of around 200 a year.
But a £220,000 project will now fund two vehicles staffed by officers.
It will also have facilities for mental health nurses to treat people.
Dyfed-Powys Police and Crime Commissioner Christopher Salmon said the Mobile Assessment and Support Team (MAST) units could be operational by the end of the summer.
The force said mental health detentions cost the taxpayer around £313,000 every year.
The aim is to decrease detention figures by 80% and save the force £249,200 in 2014-15.
The Mental Health Act stipulates that police cells are supposed to be a last resort.
"For a number of reasons, police cells are regularly used for those suffering with potentially traumatic episodes," said Mr Salmon.
"MAST is the innovative alternative. It will provide the most appropriate service to people in mental distress at the earliest opportunity and save time and money for the police, ambulance and health services."
Police cells are used to hold individuals with mental health issues when health services are stretched or when the individual has drunk too much or is being violent.
Dyfed-Powys Police managed 176 such detentions in the 10 months up to February 2013.
Three of those resulted in a crime being recorded and, on average, it took eight hours 48 minutes in detention for a person to be seen by the appropriate mental health team.
The project has received £90,000 from the Home Office and £60,468 from Dyfed-Powys Police, Hywel Dda Health Board, Powys Health Board and the Welsh Ambulance Service.
The project will cost £220,675 in 2014-15.
Among the other services provided will be a 24-hour on-call phone advice service, with access to specific advice for under-25s.