<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-12-31</periodOfReport>

    <issuer>
        <issuerCik>0000099780</issuerCik>
        <issuerName>TRINITY INDUSTRIES INC</issuerName>
        <issuerTradingSymbol>NYSE/TRN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001116073</rptOwnerCik>
            <rptOwnerName>ECHOLS LELDON E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2525 N. STEMMONS FREEWAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75207</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Trinity Phantom Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-12-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>13316</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>20.59</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>13316</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>58046</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The Trinity Phantom Stock Units were accrued under the Trinity Industries, Inc. Deferred Plan for Directors Fees.  Stock units are converted at &quot;1 - for - 1&quot; (a rate of one stock unit per one share of Trinity common stock).  Settlement of the account will be in cash after the reporting person's retirement.</footnote>
        <footnote id="F2">On November 1, 2018, the spin-off of Arcosa, Inc. resulted in the reporting person's ownership of 13,034 additional units.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Christina Maldonado  For: Leldon E. Echols</signatureName>
        <signatureDate>2018-01-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2018-12-31
0000099780
TRINITY INDUSTRIES INC
NYSE/TRN
0001116073
ECHOLS LELDON E
2525 N. STEMMONS FREEWAY
DALLAS
TX
75207
1
0
0
0
Trinity Phantom Stock Units
0
2018-12-31
4
A
0
13316
20.59
A
Common Stock
13316
58046
D
The Trinity Phantom Stock Units were accrued under the Trinity Industries, Inc. Deferred Plan for Directors Fees.  Stock units are converted at "1 - for - 1" (a rate of one stock unit per one share of Trinity common stock).  Settlement of the account will be in cash after the reporting person's retirement.
On November 1, 2018, the spin-off of Arcosa, Inc. resulted in the reporting person's ownership of 13,034 additional units.
Christina Maldonado  For: Leldon E. Echols
2018-01-03