QGIS calculate coverage density

Question

I have a survey line plan (a grid of lines along which to acquire data - dark lines in picture). Each line images data out to either 150m or 300m from the centre line. I have visualised this by making the 'Simple Line' width the appropriate width based on a column in my data. Is is possible to calculate the density of coverage from this? What I want to know is how many times an area is imaged, e.g. 1 pass = only seen once = 100%, 2 passes = seen from 2 passes = 200%, etc. The lines radiating out will only have 1 pass where they extend beyond the main grid, but may have 500% where they near the site centre. I don't know if any of the 'line density' options would work as I'm not looking at real data (beyond the line itself), I'm looking at a width projection of the line. Would I have to create a Polygon of each line?

Using Erik's Answer below, I now have categorised coverage density - This is a mini test example for clarity.

Answer 1

Add an ID to your centerlines, then buffer them so the polygons will be as wide as your swaths. Then run the SAGA tool polygonselfintersection on the buffers. No need to provide a key field.

You can now count the number of pipes in the new field ID and add 1 in order to determine how many times an area will be covered by your survey. Which actually is not as trivial as I thought it was, sorry.