@Daveosaurus @vathpela @xssfox Until very recently a small section of Portland, Oregon, USA had leading zeros in street addresses. The leading zero was used to denote a "negative" address, as the dividing line between the SW and SE sectors is a river that runs mostly south to north, but only mostly. As a result, the same addresses with and without a leading zero could be valid addresses a few blocks away from each other, but on opposite sides of a major interstate freeway, two other highways, and a steep hillside. (The steep hillside and the river being why all traffic from the south is routed through a narrow bottleneck.) So the biggest problem there was software used to route emergency services to 0700 block of SW Gaines St. could send them to the 700 block of SW Gaines St., which can be an over 10 minute drive away from each other. Not great when you want to respond to a fire or a medical emergency.