to , rather than as a substitute for , cash provided by operating activities . the following table reconciles cash provided by operating activities ( gaap measure ) to free cash flow ( non-gaap measure ) : .
what was the percentage increase in the cash provided by operating activities from 2015 to 2016
2017 outlook f0b7 safety 2013 operating a safe railroad benefits all our constituents : our employees , customers , shareholders and the communities we serve . we will continue using a multi-faceted approach to safety , utilizing technology , risk assessment , training and employee engagement , quality control , and targeted capital investments . we will continue using and expanding the deployment of total safety culture and courage to care throughout our operations , which allows us to identify and implement best practices for employee and operational safety . we will continue our efforts to increase detection of rail defects ; improve or close crossings ; and educate the public and law enforcement agencies about crossing safety through a combination of our own programs ( including risk assessment strategies ) , industry programs and local community activities across our network . f0b7 network operations 2013 in 2017 , we will continue to align resources with customer demand , maintain an efficient network , and ensure surge capability with our assets . f0b7 fuel prices 2013 fuel price projections for crude oil and natural gas continue to fluctuate in the current environment . we again could see volatile fuel prices during the year , as they are sensitive to global and u.s . domestic demand , refining capacity , geopolitical events , weather conditions and other factors . as prices fluctuate , there will be a timing impact on earnings , as our fuel surcharge programs trail increases or decreases in fuel price by approximately two months . continuing lower fuel prices could have a positive impact on the economy by increasing consumer discretionary spending that potentially could increase demand for various consumer products that we transport . alternatively , lower fuel prices could likely have a negative impact on other commodities such as coal and domestic drilling-related shipments . f0b7 capital plan 2013 in 2017 , we expect our capital plan to be approximately $ 3.1 billion , including expenditures for ptc , approximately 60 locomotives scheduled to be delivered , and intermodal containers and chassis , and freight cars . the capital plan may be revised if business conditions warrant or if new laws or regulations affect our ability to generate sufficient returns on these investments . ( see further discussion in this item 7 under liquidity and capital resources 2013 capital plan. ) f0b7 financial expectations 2013 economic conditions in many of our market sectors continue to drive uncertainty with respect to our volume levels . we expect volume to grow in the low single digit range in 2017 compared to 2016 , but it will depend on the overall economy and market conditions . one of the more significant uncertainties is the outlook for energy markets , which will bring both challenges and opportunities . in the current environment , we expect continued margin improvement driven by continued pricing opportunities , ongoing productivity initiatives , and the ability to leverage our resources and strengthen our franchise . over the longer term , we expect the overall u.s . economy to continue to improve at a modest pace , with some markets outperforming others. .