Taking her for short car rides in the carrier will help get her used to the feeling of being transported in the small space. (tailsinc.com)
What I often recommend to clients is to take pets on short car trips for 10 - 15 minutes at a time so their pets can get used to trips away from home. (blog.petmeds.com)
You can try taking your dog in the carrier for short car rides so he will be used to travelling in it. (petsmagazine.com.sg)