Drivers with car bumper stickers are more aggressive. A study of drivers found that those with cars “personalized” with bumper stickers and ornaments are more likely to act out anger on the road by flashing lights, tailgating and blocking other drivers. The more markers there are on a car, the more likely the driver is to exhibit road rage when feeling provoked — such as after being cut off. The specific message made no difference — even when innocuous, such as “baby on board.”