average highway revenue equipment owned leased total age ( yrs. ) .
[['highway revenue equipment', 'owned', 'leased', 'total', 'average age ( yrs. )'], ['containers', '33633', '25998', '59631', '8.0'], ['chassis', '22086', '26837', '48923', '9.6'], ['total highway revenue equipment', '55719', '52835', '108554', 'n/a']]
capital expenditures our rail network requires significant annual capital investments for replacement , improvement , and expansion .these investments enhance safety , support the transportation needs of our customers , and improve our operational efficiency .additionally , we add new locomotives and freight cars to our fleet to replace older , less efficient equipment , to support growth and customer demand , and to reduce our impact on the environment through the acquisition of more fuel-efficient and low-emission locomotives .2015 capital program 2013 during 2015 , our capital program totaled $ 4.3 billion .( see the cash capital expenditures table in management 2019s discussion and analysis of financial condition and results of operations 2013 liquidity and capital resources , item 7. ) 2016 capital plan 2013 in 2016 , we expect our capital plan to be approximately $ 3.75 billion , which will include expenditures for ptc of approximately $ 375 million and may include non-cash investments .we may revise our 2016 capital plan if business conditions warrant or if new laws or regulations affect our ability to generate sufficient returns on these investments .( see discussion of our 2016 capital plan in management 2019s discussion and analysis of financial condition and results of operations 2013 2016 outlook , item 7. ) equipment encumbrances 2013 equipment with a carrying value of approximately $ 2.6 billion and $ 2.8 billion at december 31 , 2015 , and 2014 , respectively served as collateral for capital leases and other types of equipment obligations in accordance with the secured financing arrangements utilized to acquire or refinance such railroad equipment .as a result of the merger of missouri pacific railroad company ( mprr ) with and into uprr on january 1 , 1997 , and pursuant to the underlying indentures for the mprr mortgage bonds , uprr must maintain the same value of assets after the merger in order to comply with the security requirements of the mortgage bonds .as of the merger date , the value of the mprr assets that secured the mortgage bonds was approximately $ 6.0 billion .in accordance with the terms of the indentures , this collateral value must be maintained during the entire term of the mortgage bonds irrespective of the outstanding balance of such bonds .environmental matters 2013 certain of our properties are subject to federal , state , and local laws and regulations governing the protection of the environment .( see discussion of environmental issues in business 2013 governmental and environmental regulation , item 1 , and management 2019s discussion and analysis of financial condition and results of operations 2013 critical accounting policies 2013 environmental , item 7. ) item 3 .legal proceedings from time to time , we are involved in legal proceedings , claims , and litigation that occur in connection with our business .we routinely assess our liabilities and contingencies in connection with these matters based upon the latest available information and , when necessary , we seek input from our third-party advisors when making these assessments .consistent with sec rules and requirements , we describe below material pending legal proceedings ( other than ordinary routine litigation incidental to our business ) , material proceedings known to be contemplated by governmental authorities , other proceedings arising under federal , state , or local environmental laws and regulations ( including governmental proceedings involving potential fines , penalties , or other monetary sanctions in excess of $ 100000 ) , and such other pending matters that we may determine to be appropriate. .

Question: what percentage of total highway revenue equipment owned is containers?
Answer: 60%