Table 2: Liquid v. Transmission Systems Characteristics,
Hazardous Liquid pipelines,Gas transmission pipelines
~ 300 operators ,~ 900 operators 
~ 50 large operators ,~ 90 large operators 
~ 350 accidents/year ,~ 130 incidents/year 
More of infrastructure data in annual reports ,Less infrastructure data in annual reports 
Integrity Management inspection data for most operators ,Less Integrity Management inspection data for operators 
Overall – more data to work with ,Overall – less data to work with
"SOURCE: U.S. Department of Transportation, Pipeline and Hazardous Materials Safety Administration, http://www.phmsa.dot.gov",