What does it mean when a moving vehicle is showing a flashing amber beacon?

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What does it mean when a moving vehicle is showing a flashing amber beacon?

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Different coloured beacons warn of different types of vehicle needing special attention. Blue beacons are used on emergency vehicles that need priority. Green beacons are found on doctors’ cars. Amber beacons generally denote slower moving vehicles, which are often large. These vehicles are usually involved in road maintenance or local amenities and make frequent stops.