Route color coding.
In navigation programs currently route to go is shown in single colour.
It can be colour coded to show descent and ascent, with intensity of colour changing according to steepness.
That would decrease risks when overtaking, as descents are hard to spot, and another car can be hiding there.
Current maps can be updated, when there are changes in altitude not matching ones known in app. No manual work would be needed; averages of reporting can be used.