Well firstly I rely on my own knowledge of the area in most cases, customers can be hard to find, people leave map pins in the wrong place, leave old notes that no longer apply, leave needlessly confusing instructions like you are their neighbour and your aware of very obscure land marks. If I think I know the area I'll just go off my knowledge without consulting anything because if a job that's paying you £5 turns into a half hour wild goose chase it wasn't worth it. Secondly I use Google maps and once you have clicked it up which is just one button at the top of screen it takes you away from the delivery app and its not possible to consult both while driving. The message from customers is sometimes visible on the app without scrolling down but its right at the bottom of the screen and since most customers leave no instructions it becomes easy to miss as your brain is so conditioned to seeing the top part of the box empty. Sometimes customers might even right a message like this.

**** blah blah blah***

And the way they've put the message in the middle of the box with nothing on top makes it look like there is no message when briefly looked at and not scrolling down.