It is also super common to use an internal gear hub of some variety. Shimano Nexus 7 can be made to be fairly narrow if you decide to forgo a roller brake. I think the Nexus 8 as well, but not as much so. Sturmy-Archer 3 speed is also a very common option. 135mm disk Alfine won't work for obvious reasons. But low grade carbon steel *could* be nade to fit most any hub if so inclined.
The advantage is getting rid of a problematic risk prone derailleur and failure proof any chain line or chain drop concerns. Set & forget.
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I shouldn't have to "make myself more visible;" Drivers should just stop running people over.
Car dependency is a tax.