I am the last person to write about physics. In high school I recall a particularly excruciating segment on optics, which left me cross-eyed. I have, however, seen a lot of crunched trees in cars and have a suggestion or two on how to get them from point A to point B without damage.
Bonsai should probably not spend much of their time in cars, but now and then they do, and when they do, we should consider them as infants. If the car were to stop abruptly—say, if it hit a tree—what will happen to the bonsai?
If you can say without hesitation, “Nothing!” there is no reason to read further. If on the other hand you have to stop and think about it, perhaps take a look at these drawings:
Should your trees be in this orientation in the car, all is well. You will not destroy your hard earned work should you be in a car chase and it go ill, ending with a crunched hood. If you are in a car chase you likely have other things on your mind, but at least you will have peace of mind that the crown of your tree is less likely to come falling forward, losing the crown, or mangling some wiring.
With this tree orientation it may not take a crunched hood to have it topple forward. Even a light tap on the brakes might do it.
Once well positioned, soil bags are useful to snug up around your pots so they don’t take a tour of your trunk. At Suzuki’s place we made blocks by wrapping fabric around thick comic books, fastened with duct tape. We’d cobble these together from the front of the van to the back and make a snug fit so that if the brakes were hit, nothing would move an inch.
But before tucking them in, all trees should have the orientation described above—with the crowns leaning toward the back of the vehicle. If in your car chase the chasing vehicle hits you from behind, never mind all the above. In fact, it is best to reverse these suggestions. As a last suggestion, consider avoiding car chases when transporting bonsai.