The paper reports results of measurements of methane emissions from underground distribution mains and services. In the program, leakage from underground distribution systems is estimated by combining leak measurements with historical leak record data and the length of underground pipe to determine the average leakage rate per unit length of pipe. The leakage rate per mile is multiplied by the miles of pipe to estimate the total leakage of a series of progressively larger laminar flow elements (LFEs) that can rapidly and very accurately measure a pressure differential across the LFE and be converted into a flow rate.