|Mode or source||Percentage of total||All oil spills (gallons)|
|Maritime tank vessels||37.4||7,245,027|
|Maritime nontank and other vessels||18.5||3,584,388|
|Highway, rail, and other transportation||1.5||285,191|
|Nontransportation structures and facilities||3.7||723,172|
|Unknown and other||6.7||1,299,139|
NOTE: Percentages may not add to 100 because of independent rounding.
SOURCE: U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics, calculations using data in table 15-5.