f0b7 positive train control 2013 in response to a legislative mandate to implement ptc by the end of 2015 , we expect to spend approximately $ 335 million during 2012 on developing and deploying ptc . we currently estimate that ptc in accordance with implementing rules issued by the federal rail administration ( fra ) will cost us approximately $ 2 billion by the end of 2015 . this includes costs for installing the new system along our tracks , upgrading locomotives to work with the new system , and adding digital data communication equipment so all the parts of the system can communicate with each other . during 2012 , we plan to continue testing the technology to evaluate its effectiveness . f0b7 financial expectations 2013 we are cautious about the economic environment but anticipate slow but steady volume growth that will exceed 2011 levels . coupled with price , on-going network improvements and operational productivity initiatives , we expect earnings that exceed 2011 earnings . results of operations operating revenues millions 2011 2010 2009 % (  % ) change 2011 v 2010 % (  % ) change 2010 v 2009 .
what percentage of total revenue in 2011 was freight revenue?
we generate freight revenues by transporting freight or other materials from our six commodity groups . freight revenues vary with volume ( carloads ) and average revenue per car ( arc ) . changes in price , traffic mix and fuel surcharges drive arc . we provide some of our customers with contractual incentives for meeting or exceeding specified cumulative volumes or shipping to and from specific locations , which we record as reductions to freight revenues based on the actual or projected future shipments . we recognize freight revenues as shipments move from origin to destination . we allocate freight revenues between reporting periods based on the relative transit time in each reporting period and recognize expenses as we incur them . other revenues include revenues earned by our subsidiaries , revenues from our commuter rail operations , and accessorial revenues , which we earn when customers retain equipment owned or controlled by us or when we perform additional services such as switching or storage . we recognize other revenues as we perform services or meet contractual obligations . freight revenues for all six commodity groups increased during 2011 compared to 2010 , while volume increased in all except intermodal . increased demand in many market sectors , with particularly strong growth in chemical , industrial products , and automotive shipments for the year , generated the increases . arc increased 12% ( 12 % ) , driven by higher fuel cost recoveries and core pricing gains . fuel cost recoveries include fuel surcharge revenue and the impact of resetting the base fuel price for certain traffic , which is described below in more detail . higher fuel prices , volume growth , and new fuel surcharge provisions in renegotiated contracts all combined to increase revenues from fuel surcharges . freight revenues and volume levels for all six commodity groups increased during 2010 as a result of economic improvement in many market sectors . we experienced particularly strong volume growth in automotive , intermodal , and industrial products shipments . core pricing gains and higher fuel surcharges also increased freight revenues and drove a 6% ( 6 % ) improvement in arc . our fuel surcharge programs ( excluding index-based contract escalators that contain some provision for fuel ) generated freight revenues of $ 2.2 billion , $ 1.2 billion , and $ 605 million in 2011 , 2010 , and 2009 , respectively . higher fuel prices , volume growth , and new fuel surcharge provisions in contracts renegotiated during the year increased fuel surcharge amounts in 2011 and 2010 . furthermore , for certain periods during 2009 , fuel prices dropped below the base at which our mileage-based fuel surcharge begins , which resulted in no fuel surcharge recovery for associated shipments during those periods . additionally , fuel surcharge revenue is not entirely comparable to prior periods as we continue to convert portions of our non-regulated traffic to mileage-based fuel surcharge programs . in 2011 , other revenues increased from 2010 due primarily to higher revenues at our subsidiaries that broker intermodal and automotive services. .