QGIS » QGIS Application

I'd like to be able to reduce the amount of labels (roads/highways) in this instance where they factor in different road categories.

Currently, with "merge connected lines to avoid duplicate labels" lots of labels are drawn for the highways (see attached image, in red).

That's more than I'd like to see and is a result of the rule based styling where highway segments are broken up by bridges.
Each highway segment between bridges gets a label and creates a lot of clutter.

Not sure what a good option would be to alleviate this.

Considering that all bridges are within a certain length that line segments could be merged that have a tolerance to ignore small features that separate them.
Or something that is topology based.

I can provide some sample data to test this on with my current rule based labels and styles if requested.

I tried experimenting with "Suppressing labeling of features smaller than" and entering some mm values, but when I enter values greater than say 10, ALL the labels disappear! A value of 1mm generates tonnes of labels. This might be a bug... not sure.