iOS Google Maps shortcutUpdate 2018-12-26: since iOS 12 you can easily integrate Shortcuts with Siri, allowing you to launch directions in Google Maps with your voice. Google "ios google maps siri shortcuts" on instructions how to add this functionality.
This makes the approach below obsolete.
Adding a Google Maps shortcut to the home screen
Using the form below on iOS allows you to create a new icon on your home screen, which opens a route in the Google Maps app. Instead of selecting often-typed locations in the Google Maps app itself, you simply press the created home screen shortcut instead.
After you fill out and submit the form below, iOS will ask you to install a new profile. If you accept, then this will add the shortcut to your home screen. This can be a timesaver if you regularly drive the same route.
It's possible to not fill out a destination address. In that case, your current location is used (if available).
The difference between future current location and current location can be understood as follows: when you leave the source address empty (recommended), Google Maps will build a route from wherever you are at the moment of using the shortcut. When leaving the destination address empty, however, Google Maps will build a route to wherever you were when you created the shortcut. This can be handy if you want to add a route shortcut from wherever you will be later, to wherever you are now (at school, work, etc.).
Deleting the shortcut
Besides deleting the home screen icon, you should delete the installed profile under Settings > General > Profiles.