In a lot of older areas the roads were built just big enough for farm to market purposes[1] either officially (as in Texas) or unofficially. This resulted in narrow, twisty & curvy roads that encourage people to drive slower and safer.
The safer a road is perceived to be through visual cues (wider, straighter, less hilly, etc) the faster drivers will go. Hence why in Seattle and other cities dangerous (read wide, "safe" feeling) roads are being put on a diet, and going from 4 lanes to 2 lanes with a center turn lane and bike lanes (sadly usually unprotected). The same thing is being done in Denmark, where they actually add curves & planters to the roads to force cars to curve and feel unsafe, which ultimately results in safer streets for everyone involved.
Another strategy that I've heard has better results is eliminating sidewalks and getting rid of jaywalking laws, so that traffic of all types are forced to intermingle at much lower speeds.
[1] - https://en.wikipedia.org/wiki/Farm-to-market_road