For moving objects like vehicles, people and animals, you need a high shutter speed to freeze the subject in the image.
Having a slow shutter speed can create motion blur. You would use a slow shutter speed for subjects like a waterfall, when you want to create motion blur in the water – but you’d need to use a tripod to stop the whole picture from being blurry as hand-holding your camera with a low shutter speed can create camera shake. For moving objects like vehicles, people and animals, you need a high shutter speed to freeze the subject in the image.