Starting July first, California drivers will have to use a hands-free device if they want to talk legally on their cell phones while driving. A study by The Public Policy Institute of California finds once that happens, the state is likely to see about 300 fewer traffic fatalities a year. Typically there are about four-thousand traffic deaths annually. The study finds that requiring the hands-free devices has the biggest impact in rush-hour traffic, when the roads are wet or there is bad weather. The P-P-I-C researchers recommend the strongest enforcement of hands-free laws at those times. The findings are based on statistics from other states which have adopted similar measures. The research differs from other studies which have claimed hands-free devices are no safer than hand-held cell phones while driving.