The National Weather Service says severe dust storms are bringing visibility down to zero in some areas along Interstate 10 between Phoenix and Tucson. Winds of up to 50 mph are blowing dust across the highway and a weather service observer reported that visibility was down to zero near Picacho Peak State Park. The Arizona Department of Public Safety said no major problems have yet been reported. Drivers caught in such zero-visibility conditions should not try to continue. Instead, drive as far off the right side of the highway as possible, turn off your lights, set the parking brake and stay off the brake pedal so brake lights stay off. The dust warning is in effect until 6 p.m. Saturday.