Raspberry Pi Car Speed Detector

I think you're seeing this from a "what is legal" standpoint versus the author's issue with "what is safe". If the speed limit is 25 MPH and people regularly go 50 MPH, endangering the lives of the residents, raising the limit so they can legally go 50 MPH only means they are legally endangering the lives of the residents. They don't slow down at all and are rather likely to speed up, as many drivers view the speed limit as a minimum instead of a maximum.

For example, on my road, which is not in a neighborhood and is a country road that serves as a connector between two highways, the speed limit was raised from 35 MPH to 45 MPH several years ago. Accordingly, traffic went from averaging 50-55 MPH to now averaging 65-70 MPH with occasional amateur race car drivers going by so fast you can't tell the type of car they drive. I have found it treacherous to check my mailbox and mow my lawn at certain times of the day (mainly "rush hour" and, oddly enough, Sunday afternoons). Twice in the past five years my mailbox has been obliterated by a speeder losing control of their vehicle and running off the road because they were driving too fast and/or distracted, one time right in front of my eyes as I was walking to the mailbox.

Generally, if you set a speed limit on a long straight road, you can expect the public to exceed it by at least 10 MPH. This effect has been observed by the GHSA[1] and IIHS[2] and is easily researched privately if one is so inclined.

[1] http://www.ghsa.org/html/media/pressreleases/2016/20160412sp... [2] http://www.iihs.org/iihs/sr/statusreport/article/51/4/3