In a map used for bicycle navigation, I wanted to include highways because they are important landmarks/barriers. But I wanted to de-emphasize them relative to the street network so I made them partially transparent. The problem is that overlapping links of these roads brighten as per the image below, when I would like them to just be uniformly neutral. To clarify, Martha Road is bikeable, and therefore at 100% alpha, while a series of tunnels and overpasses directly to its north are unbikeable, and therefore transparent. The two types of road are in the same layer, with a rule-based styling.
What symbology properties do I have to modify so that overlapping transparent features blend into each other?