our access to commercial paper and reduce our credit ratings below investment grade , which would prohibit us from utilizing our sale of receivables program and significantly increase the cost of issuing debt .
we are dependent on two key domestic suppliers of locomotives 2013 due to the capital intensive nature and sophistication of locomotive equipment , high barriers to entry face potential new suppliers .
therefore , if one of these domestic suppliers discontinues manufacturing locomotives , we could experience a significant cost increase and risk reduced availability of the locomotives that are necessary to our operations .
we may be affected by acts of terrorism , war , or risk of war 2013 our rail lines , facilities , and equipment , including rail cars carrying hazardous materials , could be direct targets or indirect casualties of terrorist attacks .
terrorist attacks , or other similar events , any government response thereto , and war or risk of war may adversely affect our results of operations , financial condition , and liquidity .
in addition , insurance premiums for some or all of our current coverages could increase dramatically , or certain coverages may not be available to us in the future .
item 1b .
unresolved staff comments item 2 .
properties with operations in 23 states , we employ a variety of assets in the management and operation of our rail business .
these assets include real estate , track and track structure , equipment , and facilities .
we own and lease real estate that we use in our operations , and we also own real estate that is not required for our business , which we sell from time to time .
our equipment includes owned and leased locomotives and rail cars ; heavy maintenance equipment and machinery ; other equipment and tools in our shops , offices and facilities ; and vehicles for maintenance , transportation of crews , and other activities .
we operate numerous facilities , including terminals for intermodal and other freight ; rail yards for train-building , switching , storage-in-transit ( the temporary storage of customer goods in rail cars prior to shipment ) and other activities ; offices to administer and manage our operations ; dispatch centers to direct traffic on our rail network ; crew quarters to house train crews along our network ; and shops and other facilities for fueling , maintenance , and repair of locomotives and repair and maintenance of rail cars and other equipment .
we spent approximately $ 2.2 billion in cash capital during 2006 for , among other things , building and maintaining track , structures and infrastructure ; upgrading and augmenting equipment ; and implementing new technologies ( see the capital investments table in management 2019s discussion and analysis of financial condition and results of operations 2013 liquidity and capital resources 2013 financial condition , item 7 ) .
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 ) .
track 2013 the railroad operates on 32339 main line and branch line route miles in 23 states in the western two-thirds of the united states .
we own 26466 route miles , with the remainder of route miles operated pursuant to trackage rights or leases .
route miles as of december 31 , 2006 and 2005 , were as follows : 2006 2005 .

<i>2006</i>
<i>2005</i>
Main line
27,318
27,301
Branch line
5,021
5,125
Yards, sidings and other lines
19,257
20,241
Total
51,596
52,667

.

Question: Analyse this data from a financial earnings document. what percent of total route miles are main line in 2006?
Choices:
-0.52946
0.52946
0.51869
0.00626
0.52913
Correct choice index: 1