A Street Sixteen Amos Wide
A public route sixteen amos wide is the classic starting measurement for reshus harabim.
The width of the road in the midbar
Sixteen amos is the classic width associated with the public roads in the midbar. A city street that reaches that width may satisfy one of the central physical features of reshus harabim.
The measurement is a halachic one, expressed in amos. Its modern equivalent depends on the shiur being followed, so a careful analysis states the standard rather than switching silently between measurements.
What part of a modern street is measured
A modern street can include travel lanes, medians, parking lanes, bicycle lanes, service roads, and sidewalks. The question is which parts form one public route and which fixed divisions interrupt or separate it.
Painted lines ordinarily do not create walls. A substantial median or permanent obstruction may affect the form of the route, but its dimensions and the public movement around it must be examined.
Width is the beginning, not the entire definition
A road can be sixteen amos wide and still raise further questions about whether it is open from end to end, freely used by the public, mefulash through the city, and subject to the required level of public passage.
Conversely, a network of connected public streets cannot be dismissed by measuring only one narrow segment. The Rav must identify the route being analyzed and apply the complete definition accepted in his psak.