The design and construction of fire engines focuses greatly on the use of both active and passive warnings. Passive visual warnings involve the use of high contrast patterns to increase the noticeability of the vehicle. These types of warnings are often seen on older vehicles and those in developing countries. More modern designs make use of retroreflectors to reflect light from other vehicles. Vehicles will also often have these reflectors arranged in a chevron pattern along with the words fire or rescue. European countries commonly use a pattern known as battenburg markings. Along with the passive warnings, are active visual warnings which are usually in the form of flashing colored lights (also known as "beacons" or "lightbars"). These flash to attract the attention of other drivers as the fire truck approaches, or to provide warning to drivers approaching a parked fire truck in a dangerous position on the road. While the fire truck is headed towards the scene, the lights are always accompanied by loud audible warnings such as sirens and air horns.