I asked Claude again to compare Rio and Notting Hill carnival crime specifically and while I need to fact check in more detail, I think it brought up some interesting points. Apologies for the big bold letters :
1. Different weapon-violence baseline entirely
UK knife crime is a specific phenomenon: bladed weapons carried mainly by young people, heavily tied to gang territoriality and drug-supply networks ("county lines"), with carrying itself often defensive as much as offensive — a self-perpetuating arms-race dynamic among teenagers. Brazil's serious violence, by contrast, is predominantly firearms-based and organized-crime-driven, rooted in favela drug-trafficking factions clashing with each other or police — a different weapon, different actors, and critically, geographically segregated from where blocos actually happen (hence the standard advice to simply avoid favela areas). Notting Hill Carnival runs directly through the same urban fabric its youth-gang tension exists in so doesn't have a segregated "avoid this district" option the way Rio effectively does.
2. Dispersal vs. concentration (structural, from last message)
This is probably the single biggest factor for the specific nuisances you named. Hundreds of blocos spread across a huge city over weeks means no one street, no one set of residents, absorbs the full brunt repeatedly. Notting Hill compresses ~2 million people into one 3.5-mile residential corridor over 48 hours — the same front doors, the same gardens, the same pavements, hit at maximum intensity, every single year.
3. Enforcement culture and actual penalties
Rio genuinely fines public urination as an enforced offense. Notting Hill's council response to the equivalent behavior is softer and more remedial — garden-clearance services, a noise complaints line, post-event cleanup — reactive and compensatory rather than punitive and preventive.
4. Residential zoning around the biggest parties
Some Rio blocos run through quiet residential neighborhoods, but they're explicitly marketed as the calmer, family-friendly tier — the truly massive "megablocos" concentrate in downtown, commercial, or beachfront zones, not primarily along people's front doors.