There can be lots of reasons you're running late, and often traffic is the challenge. But there is an app that can keep people updated with where you are and when you're likely to arrive. It is especially helpful as it means you don't have to talk or text while driving. If you are a passenger then it is far simpler than trying to type or tell someone where you are, how fast you're moving, and what your expected arrival time could be.
There are several variants of the app, but all provide the same functionality. See them here. Try it out on your commute to see what it is like.