Icon overlapping should be avoided

[marians]

Especially in the lower zoom levels (with many AED markers in the viewport), markers tend to overlap and thus degrade readability of the map.

Two options come to my mind:

1. Use smaller markers, especially in lower zoom levels
2. Use clustering. Leaflet Markercluster might be an option (https://github.com/Leaflet/Leaflet.markercluster, https://www.mapbox.com/mapbox.js/example/v1.0.0/leaflet-markercluster/). It can be tweaked heavily.
3. Use a Google Earth style "spiderfier". See https://github.com/jawj/OverlappingMarkerSpiderfier-Leaflet and demos.