PHOENIX --- Arizona yesterday began enforcing one of the toughest DUI laws in the U.S. The law creates a new classification for "superextreme" DUI offenders whose blood-alcohol concentration registers 0.20 percent or above. That's more than double the legal limit of 0.08 percent. Newly enacted penalties for drunk drivers include mandatory ignition-interlock devices for first-time offenders, higher fines and a minimum of 45 days in jail for superextreme DUI convictions, KMSB-TV News reported. Interlock devices, located beneath a vehicle's dash, require a clean breath sample to start the car. The driver has three attempts to blow a clean breath sample before the device shuts down. After that, a technician must recalibrate the device for the car to operate. In 2006, Arizona had 585 alcohol-related fatalities on the road, up 15 percent from 2005's figure.