I have started looking into the styles which would be better suited for car navigation and I would like to outline few points to continue the discussion on it over here.

Before getting into the technical aspects, let's review how we use the navigation app while in the car. There are two modes of operation, road selection/review and navigation. In the first mode, we can hold the phone in the hands and would be great to have detailed maps. In the second one, with the device significantly further away than in the hands, there is only fast glance that should provide sufficient information. I think that switching between the modes is needed for proper operation and that can be provided only if the software and styles work hand-in-hand. Its somewhat similar to the situation of the day/night mode switching, which is needed for longer car trips as well. Same arguments go for cycling.

From technical aspects, I would suggest to approach it as follows:

* Define not a single style, but style families. So, in https://github.com/otsaloma/whogo-maps/tree/master/maps, we would have Cartago grouping Cartago and Cartago Car. Similar would be for Mapbox Traffic (Day and Night) and OSM Scout (Day, Night, Car Day, Car Night). Users would have to just select Cartago, Mapbox Traffic, or OSM Scout for these combinations. These groups should be easy to define by extending current JSON definition.

* Car styles in the group, when defined, would have larger fonts and wider roads. As an alternative, each style in the group could have "Zoom factor" defined that would use zooming feature of Mapbox GL to blow up the map. This zoom factor should be multiplied by the factor selected in the Preferences.

* Day and night modes are swapped automatically or via Preferences by user.

* Car and regular modes are swapped by pressing Start/Resume and by Stop in Navigation.

Note that while Mapbox zoom can help with the transition, it does effectively reduce your map DPI. One can argue that it doesn't matter much when navigating, its probably should be a choice for developers.

Thoughts?