WASHINGTON (AP) — A sheriffs' organization is broadening its concerns about the popular Waze (pronounced "ways") mobile traffic app. Now it says a feature that lets drivers warn others about nearby police cruisers not only presents a threat to police safety, it also interferes with the ability to write speeding tickets.

The National Sheriffs' Association says speed enforcement makes roads safer. The trade group says that if people know where police might be parked on highways, it makes it more difficult to catch people breaking the law.

Waze is a combination of GPS navigation and social networking. Fifty million users in 200 countries turn to the free service for warnings about nearby congestion, car accidents, speed traps, traffic cameras, construction zones, potholes, stalled vehicles or unsafe weather conditions.