It's OK to look at a map on your smartphone while driving in California. It's also legal to talk on the phone at the wheel - as long as your device is hands-free. You even may wear Google Glass. Except when you may not. California currently bars drivers younger than 18 from using cell phones and similar devices at all; drivers older than that can use hands-free versions of handheld devices - as long as both ears aren't covered. (Cal. Veh. Code §§ 23123-24.) But recent court decisions have made the road map for using other electronics while driving more complex: What one California Highway Patrol officer may see as an unsafe, illegal use, a judge may view as within the bounds of the law. The state vehicle code doesn't mention devices like Google Glass, for example. Yet in 2013 Cecilia Abadie of San Diego, who wore the computerized eyewear while driving, was cited under the code section that bars drivers from watching TV or video monitors. Her attorney, William Concidine, argued that she didn't violate the law because her Glass was switched off, and the traffic court judge threw out the ticket. But that left unanswered the question of whether Abadie should have been able to use Glass while driving. (The device is also drawing censure off the road. Numerous bars in California and elsewhere have banned wearing the computerized accessory; and in San Francisco a reporter wrote that someone on the street snatched the device from his face and smashed it, while a Glass-wearer claimed bar patrons who thought she was recording them assaulted her.) And Glass isn't the only device raising new questions. California's Fifth District Court of Appeal ruled in February that Steven Spriggs of Fresno was wrongly ticketed for looking at a map on his iPhone while driving. The court said Spriggs was in the clear because he wasn't talking: "We conclude that the statute means what it says - it prohibits a driver only from holding a wireless telephone while conversing on it." (People v. Spriggs, 224 Cal. App. 4th 150 (2014).) Chris Cochran, spokesman for the state's Office of Traffic Safety, notes that distracted driving can't be measured the way a driver's level of intoxication can. So enforcing the device-related vehicle codes requires interpretation. Still, his office - like the National Highway Traffic Safety Administration, the American Automobile Association, and other safety organizations - advocates a strategy with no room for interpretation: "The best practice," he says, "is to hang up and drive." No state bans all cell phone use for all drivers, but twelve (plus Washington, D.C., Guam, Puerto Rico, and the U.S. Virgin Islands) have an outright ban on using handheld cell phones while driving, according to the Governors Highway Safety Association. Most states and Washington, D.C., further limit novice drivers, most ban texting, and 20 bar school bus drivers from using cell phones while driving. Yet the number of convictions in California for using a handheld cell phone while driving rose from about 300,000 in 2009 to nearly 400,000 in 2013, according to the Department of Motor Vehicles. Convictions for texting while driving jumped tenfold between 2009 and last year, when there were 27,207. (A large but unknown number of convictions for speeding or driving unsafely also involve illegal use of a cell phone, says CHP spokesman Mike Harris.) Assembly Member Jim Frazier from Contra Costa County (D-Oakley), who has sponsored several bills on cell phone use on the road, says his office is constantly learning about new technologies that could distract drivers. For the moment, he plans to amend his bill to toughen distracted-driving penalties (AB 1646) so that it also bars using either Google Glass or cell phone maps while driving.