Methods to attribute street-level natural gas leaks with vehicle-system surveys have relied mainly on indirect approaches. Several studies used plume persistence (detectable on 2 or more passes or at least one half of the passes) and width (< 160m) as methods to attribute emissions detected at the surface to underground natural gas distribution pipeline leaks . The premise of these criteria is that natural gas plumes are narrow and persistent because distribution pipeline pressures remain constant. However, there are several issues with these criteria. First, the plume length threshold (< 160m) was based on a controlled release testing (CRT) experiment in an open field . Turbulence and plume dispersion in an open field are very different than on a busy city street where wind is modified by buildings and moving vehicles. Second, using persistence as a metric assumes that there are no other natural gas sources that could be emitting continuously. For example, leaks from natural gas service lines running up the sides of buildings or customer meters (e.g., ) could be persistent sources. Third, the general focus of research on natural gas distribution pipeline leaks has narrowly framed the problem along city streets. There are many other potential natural gas sources adjacent to streets -such as customer meters, valve vaults, farm tap units, vents from heaters and boilers, and industrial sources -that may be emitting but have been poorly characterized or not characterized at all.