The relatives of people killed in traffic accidents caused by illegal billboards yesterday accused advertising companies of using heavy-handed tactics to override their concerns and keep the signs in place. Families and friends of victims want the illegal billboards removed and say that, as a result, their lives have been threatened or they have been offered bribes to not pursue the issue. Illegal advertising billboards are said to be responsible for about 12 percent of road deaths. Passengers in car collisions are often rammed against the large metal structures. Drivers are also often distracted by the signs, authorities say. Experts say there are an estimated 15,000 illegal advertising signs around Athens, in an industry that is valued at around 200 million euros per year. The relatives blame municipal authorities for turning a blind eye to the erection of illegal billboards. Local officials responded by saying that they, too, were threatened by the advertising firms when they made efforts to remove the signs.