. locomotive simulator training , operating practices , and technology all contributed to this improvement , saving approximately 21 million gallons of fuel in 2007 . 2022 free cash flow 2013 cash generated by operating activities totaled a record $ 3.3 billion , yielding free cash flow of $ 487 million in 2007 . free cash flow is defined as cash provided by operating activities , less cash used in investing activities and dividends paid