That's the reason we need to enforce speed limit. People are terrible at assessing what's safe. Even if they can somehow manage to assess their personal safety

That's the reason we need to enforce speed limit. People are terrible at assessing what's safe. Even if they can somehow manage to assess their personal safety they have terrible judgement when it comes to other road users. You may feel very safe going over speed limit in a residential area but pedestrians, cyclists etc. won't.