A fairly regular occurrence when you do a lot of driving; you find something during your drive that should be reported (roadkill, accidents, debris, etc.). If you are on a rural road, the GPS coordinates would be ideal. But, since you are a sensible person you don’t want to take your hands off the steering wheel to fiddle with your phone.
I have a solution for iOS phones (mostly – it still will require one touch of the screen).
The solution is to use Siri and ask the question “Where am I?”

Now unfortunately, Siri doesn’t store this information, and once your screen turns off it will disappear. However, if you touch the map, the information will be transferred to the maps app. The maps app will hold the information until you are ready to deal with it.

Now when you can pull over you can use either the option to Share My Location or Mark My Location.
Selecting Share My Location brings up your share sheet.


You can also pull the panel a little higher up over the map, for more information. Like the GPS coordinates or contact options.
You can use the Mark My Location to do exactly that on the map. A red pin will display on the map, and the option to Edit the location appears.

If you choose to edit the location, a satellite view of the location opens, and you can drag and drop the pin.

Marked locations remain in the map app for later reference.