The term 'Safari Vehicles' refers to the type of vehicles used for safaris, which are typically open-air vehicles that allow passengers to observe wildlife in their natural habitats. The four-letter answer to this crossword is 'MACS', which stands for Multi-Axle Coaches. These vehicles are designed to provide a comfortable and safe ride while allowing passengers to take in the sights and sounds of the African savanna. They are usually equipped with amenities such as air conditioning, reclining seats, and large windows for optimal viewing.