Put a thermometer in the trailer and keep track of the temperature. Cold temperatures are much less of a problem unless they are extreme. The windows and vents on the trailer should be closed to avoid wind chill and frostbitten ears. Keep a thermometer in the trailer to be sure that temperatures do not get too cold. If there is a cria in the vehicle or a llama with very little wool, consider putting a blanket or coat on them to maintain their warmth.
Halters can be a problem during transportation.
Llamas are very mobile within any vehicle that gives them room the stand up and lay down. They will move throughout the trailer, even though most lay down while the vehicle is moving. The llama could easily get their halter caught on the side of the trailer despite your best efforts to prevent this. Hanging can result in an injured or dead llama. Always remove halters while traveling.