<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-05-29</periodOfReport>
    <issuer>
        <issuerCik>0000099780</issuerCik>
        <issuerName>TRINITY INDUSTRIES INC</issuerName>
        <issuerTradingSymbol>NYSE/TRN</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId>
            <rptOwnerCik>0001195484</rptOwnerCik>
            <rptOwnerName>WALLACE TIMOTHY R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Chairman, President &amp;amp; CEO</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>Restricted Stock</value></securityTitle><transactionDate><value>2003-05-29</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>87500</value></transactionShares><transactionValue><value>0</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>326663</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><derivativeSecurity><securityTitle><value>Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>17</value></conversionOrExercisePrice><transactionDate><value>2003-05-29</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>183900</value></transactionShares><transactionValue><value>0</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2004-05-29</value><footnoteId id="F1"/></exerciseDate><expirationDate><value>2013-05-29</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>183900</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>183900</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><footnotes><footnote id="F1">Option Term is Ten Years.  Options vest over 5 years at twenty percent (20%) per year beginning on the first anniversary of the grant date.</footnote><footnote id="F2">Balance does not include Indirect ownership of 1,166 shares held by a 401(k) Plan Trust for the benefit of the reporting person.</footnote></footnotes><ownerSignature><signatureName>Michael G. Fortado  For:  Timothy R. Wallace</signatureName><signatureDate>2003-06-02</signatureDate></ownerSignature></ownershipDocument>
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X0101
4
2003-05-29
0000099780
TRINITY INDUSTRIES INC
NYSE/TRN
0001195484
WALLACE TIMOTHY R
1
1
0
0
Chairman, President &amp; CEO
Restricted Stock
2003-05-29
4
A
0
87500
0
A
326663
D
Stock Option (right to buy)
17
2003-05-29
4
A
0
183900
0
A
2004-05-29
2013-05-29
Common Stock
183900
183900
D
Option Term is Ten Years.  Options vest over 5 years at twenty percent (20%) per year beginning on the first anniversary of the grant date.
Balance does not include Indirect ownership of 1,166 shares held by a 401(k) Plan Trust for the benefit of the reporting person.
Michael G. Fortado  For:  Timothy R. Wallace
2003-06-02