https://www.visitwhitemountains.com/articles/post/history-made-the-mt-washington-auto-road-paved-top-to-bottom/
For those in the Boston area, there are a few additional variations available
https://www.jessehaley.com/category/bumper-stickers
Fundementally, they're the same thing. Practically, tree wells form around the trunks of large trees that people fall into. They don't typically involve the branches. Spruce traps (in the East) are entire trees hidden under the snow with the branches holding up mostly unsupported snow. They...