A recent report from Towers Watson shows that the world is making steady progress toward usage-based insurance (UBI). That steady growth is poised to become explosive if insurers can move faster and deal with privacy concerns while delivering UBI via smartphone apps that consume little of the battery's charge. The report says market penetration has nearly doubled in less than a year and a half -- reaching 8.5% of U.S. drivers in July, up from 4.5% in February 2013. UBI has reached a milestone, with all 50 states now having programs available. Consumers want the discounts that they can get by having their usage quantified and verified. Consumers are more willing than ever to work with carriers that offer UBI programs -- meaning they will leave carriers that don't. An effective UBI program may prove to be a once-in-a-career opportunity for auto-insurance executives to resegment the market and claim a bigger share. The last time there was a change even approaching this magnitude was in the 1990s, when insurers discovered the importance of credit ratings in assessing how risky a driver is. It's time that we stopped measuring with a 12,000-mile-long tape measure -- that being the distance that old-school insurers assume someone drives each year -- and started measuring with a ruler. The mileage bands used to determine risk need to become so small that a single tank of gas could put a consumer into a new one -- and the consumer needs to know that in advance so she can make a fully informed decision about how much to drive.