Bicycle messengers (also known as bike or cycle couriers) are people who work for courier companies (also known as messenger companies) carrying and delivering items by bicycle. Bicycle messengers are most often found in the central business districts of metropolitan areas. Courier companies use bike messengers because bicycle travel is less subject to unexpected holdups in city traffic jams, and is not deterred by parking limitations, fees or fines in high density development that can hinder or prevent delivery by motor vehicle, thereby offering a predictable delivery time.