Most SLs are set by construction standards set up by the NHSI (National Highway Safety Institute).
With that said, then things can go to hell...
The NHSI sets the standards and once the road is built, local conditions take over...amount of traffic, accidents, local issues (lots of foggy days, icy conditions, wind, etc...)
Then the human factor enters into all of this...
Who's kid got a speeding ticket, which politician got a speeding ticket, whether the road was built by the un-employed BIL of the politician, who cut corners when mixing the cement or not prepping the roadbed properly...whether there's access/egress issues with side-streets, on-ramps, off-ramps...blue-hairs or pre-pubes in the area and in your lane...
Complain too?
Good luck.
Coordinating a change in the SL in an area usually involves some simple tragedy like a kid getting hit by a dump-truck or a little old lady gets t-boned while blindly backing out of a drive-way. Body-counts vary from one community to another, but count on more than a FEW before anyone has any impetus to change the SL...and generally? It goes DOWN...not up.
Good luck fighting City Hall Mr. Quixote...
