OptionalmaxLeaves out the curves wider than this.
OptionalmaxHow far the road may run straight within a curve. A longer straight ends it, so two bends apart are two curves.
It defaults to 40, or to 15% of a maxRadiusInMeters over 267, since a wide curve turns little
over 40 metres.
OptionalminLeaves out the curves turning less than this, either way.
The thresholds a stretch of road has to reach to count as a curve.
Remarks
The defaults keep the bends a passenger feels: from a country road's 40° bend on a radius of 250 metres to a hairpin. Lower
maxRadiusInMetersto keep only hard curves, such as to warn someone prone to motion sickness, or raise it to count sweeping bends too.