In QGIS I have a layer that is a MultiLineString that has many overlapping lines, which represent driving routes around the city which are generated using OSRM.
My data looks something like
[
[[a,b],[c,d],[e,f],[g,h]],
[[y,z],[a,b],[c,d],[e,f],[g,h]],
[[e,f],[g,h],[i,j],[k,l]]
]
where some segments are only recorded once, some twice, and some many more times (up to thousands of times).
How can I increase the width (line thickness) of segments of the routes based on the number of times they are overlapped?
I have a working solution using the JavaScript libraries OpenLayers and Turf but the solution is inefficient and cannot scale. See below for an example of the desired effect.

Answers that involve re-formatting the data or working in Python are within my scope.
intersecting_geom_count(). – csk Mar 06 '19 at 18:49