<?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>0001199852</rptOwnerCik>
            <rptOwnerName>FORTADO MICHAEL G</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>VP &amp;amp; Secretary</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>2000</value></transactionShares><transactionValue><value>0</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>14500</value><footnoteId id="F3"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><derivativeSecurity><securityTitle><value>Trinity Stock Units</value></securityTitle><conversionOrExercisePrice><value>0</value><footnoteId id="F1"/></conversionOrExercisePrice><transactionDate><value>2003-05-30</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>6</value></transactionShares><transactionValue><value>17.3</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>1988-08-08</value><footnoteId id="F1"/></exerciseDate><expirationDate><value>1988-08-08</value><footnoteId id="F1"/></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>6</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>5290</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>by Trust</value></natureOfOwnership></ownershipNature></derivativeSecurity><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>1750</value></transactionShares><transactionValue><value>0</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2004-05-29</value><footnoteId id="F2"/></exerciseDate><expirationDate><value>2013-05-29</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>1750</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1750</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><footnotes><footnote id="F1">The Trinity Stock Units were accrued under the Trinity Industries, Inc. Supplemental Profit Sharing Plan and will be settled upon the reporting  person's retirement or other termination of service or earlier for in service distributions under limited circumstances as provided by the plan.  Stock Units convert at a ratio of 1 to 1.</footnote><footnote id="F2">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="F3">Balance does not include Indirect ownership of 2,372 shares held by a 401(k) Plan Trust for the benefit of the reporting person.</footnote></footnotes><ownerSignature><signatureName> Michael G. Fortado</signatureName><signatureDate>2003-06-02</signatureDate></ownerSignature></ownershipDocument>
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X0101
4
2003-05-29
0000099780
TRINITY INDUSTRIES INC
NYSE/TRN
0001199852
FORTADO MICHAEL G
0
1
0
0
VP &amp; Secretary
Restricted Stock
2003-05-29
4
A
0
2000
0
A
14500
D
Trinity Stock Units
0
2003-05-30
4
A
0
6
17.3
A
1988-08-08
1988-08-08
Common Stock
6
5290
I
by Trust
Stock Option (right to buy)
17
2003-05-29
4
A
0
1750
0
A
2004-05-29
2013-05-29
Common Stock
1750
1750
D
The Trinity Stock Units were accrued under the Trinity Industries, Inc. Supplemental Profit Sharing Plan and will be settled upon the reporting  person's retirement or other termination of service or earlier for in service distributions under limited circumstances as provided by the plan.  Stock Units convert at a ratio of 1 to 1.
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 2,372 shares held by a 401(k) Plan Trust for the benefit of the reporting person.
Michael G. Fortado
2003-06-02