Maricopa County has begun installing warning devices at unbridged road crossings in an effort to keep drivers from entering flooded washes before they're barricaded.
The automated devices have warning lights that flash when activated by a system that monitors rainfall amounts and streamflow data.
The system also alerts county when to deploy to put up barricades.
Warning devices have already been installed on Patton Road at Hassayampa River, Salome Highway at Delaney Wash, Bartlett Lake Road at Camp Creek Wash and Old Stage Road at New River.
The county Flood Control District and the county Transportation Department plan to install additional devices at other locations in coming years.
Officials say nearly half of all flash flood fatalities are related to vehicles.