Not to mention car pooling, biking, and walking.
TN's Jackie Yamanaka received a letter with the above stamp, leading us to immediately research its provenance.
It turns out the U.S. Postal Service has produced a series of stamps with eco-friendly messages. One of them encourages the use of public transit. The others exhort recipients to "choose to walk," "share a ride," "maintain tire pressure," and "ride a bike."
It's also possible to purchase a stamp celebrating American infrastructure -- like Florida's Sunshine Skyway Bridge.
Just a tip in case you want to send some snail mail TN's way we haven't seen these in person yet: