From the Associated PressIndiana officials are working to formalize regulations for tornado sirens, but some counties could decide not to install them. The regulations being finalized by the Indiana Department of Homeland Security allow each county to decide whether it needs sirens.The agency recommends sirens for counties with more than four homes per acre and for urban and commercial areas with more than 2,500 people present per square mile during the day. Sirens also are recommended near major highways. The department’s general counsel, George Thompson, tells WIBC radio says some rural counties might be better served by weather radios instead of sirens. Counties will need to decide where to install sirens and when to set them off. The state requires only that sirens sound for a tornado warning. The guidelines are expected to take effect in about two months.