<?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>0001289486</rptOwnerCik>
            <rptOwnerName>Lovett Melendy 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>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>SVP &amp; Chief Admin Officer</officerTitle>
        </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>3140</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>3140</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>13683</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 3,072 additional units.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Christina Maldonado  For: Melendy E. Lovett</signatureName>
        <signatureDate>2018-01-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
[{"type": "4", "sequence": "1", "filename": "edgar.xml", "description": "PRIMARY DOCUMENT", "secsgml_size_bytes": 4238}]
X0306
4
2018-12-31
0000099780
TRINITY INDUSTRIES INC
NYSE/TRN
0001289486
Lovett Melendy E
2525 N. STEMMONS FREEWAY
DALLAS
TX
75207
0
1
0
0
SVP & Chief Admin Officer
Trinity Phantom Stock Units
0
2018-12-31
4
A
0
3140
20.59
A
Common Stock
3140
13683
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 3,072 additional units.
Christina Maldonado  For: Melendy E. Lovett
2018-01-03