Stroads are a word that strongtowns seems to have recently successfully popularized, so it is hard to find actual measurements about "stroads." However, I was able to find a little research indicating that narrower streets are correlated to fewer/less damaging traffic accidents. There's a conference paper "Narrower Lanes, Safer Streets," or have a look at these blogs that talk about it:

https://usa.streetsblog.org/2015/05/27/compelling-evidence-t...

https://thecityfix.com/blog/bigger-isnt-always-better-narrow...

Honestly I'm a bit surprised how little this has been measured. I mean obviously setting up experiments would be difficult, but you'd think more natural experiments would occur as different places try to fit weird geometries...