There is a lot of variation within the Amish community. Religious rules are set by the local bishop, so there's different rulings on such matters as whether it's OK to use electric tools at a job, whether it's OK to listen to a radio just for a weather forecast, and so on. *Most* of the Amish have no problem with the reflective triangles on their vehicles. The Schwarzentrubers are a conservative group even within the Amish.
Some who don't know the Amish assume that because they're protestant religious fundamentalists, they must be kind of dour calvinistic sorts. But they're actually pretty easygoing; they split off from the mainstream of protestant thought so long ago that they were never affected by Puritanism. Not uptight at all. There are some that come by every year during deer season and I let them hunt on my back forty acres.
