工程師估價量對單價合同的不準確影響中英文版樣本

資料內(nèi)容僅供您學習參考，如有不當或者侵權，請聯(lián)系改正或者刪除。工程師估價量對單價合同的不準確影響Abstract摘要:Thispaperdiscusstheissueofunbalancedbidpricesinunitpricehighwaycontracts.本文討論了公路的合同單價的不平衡報價的價格問題。Itanalyzesthereasonscontractorsunbalancetheirbidsandlooksforwaysthatallowpublictransportationagenciestodiscouragethispractice.分析了原因,承建商競投不平衡的方法,讓公共交通機構,勸阻這種做法,并期待。Itreviewstheresultsofastudyofquantityestimatingaccuracyof462transportationprojectsinOklahoma,andfindsthatonemethodtoreduceunbalancedbidpricesisfortheagencytoensurethatthebidquantitiesusedintheengineer'sestimateareasaccurateaspossible.它審查的數(shù)量估計在俄克拉荷馬州交通項目462個,準確的研究結果,發(fā)現(xiàn)了一個方法,以減少不平衡報價的價格是該機構,以確保中標,在工程師的估計使用量是盡可能準確。Doingsoreducestheneedforcontractorstounbalancetoprotectfixedcostsandtargetprofitonbiditemsthatwillunderrunthequantityusedintheengineer’sestimate.這樣做減少了對不平衡保護承建商投標項目,將在欠載工程師的估計采用的數(shù)量固定費用和目標利潤的需要。Dor:10.1061/(ASCE)CO.1943-7862.0000084(ASCE的)有限公司CEDatabasesubjectheadings:Estimation;Pricing;Contracts;Highwayandroadconstruction.CE數(shù)據(jù)庫主題詞:估計;定價;合同;公路和道路建設。Background:背景Thedevelopmentofaccuratepre-bidcostestimatesisfoundedonthedevelopmentofanaccuratequantityestimate(UDOT).準確的投標前費用概算的發(fā)展是建立在一個準確的數(shù)量估算(UDOT)的發(fā)展。Thisisparticularlytrueonunitpricecontractswherethecompetingconstructioncontractorsmustbidtheengineer’sestimatedquantitieseveniftheyareincorrect(SchexnayderandMayo).這一點特別對單價合同,即競爭性投標的建筑商必須工程師的估計數(shù)量,即使她們不正確(施克斯納德和Mayo)也是如此。Therearetwoadministrativefactorsthatimpacttheaccuracyofpublicengineer’sestimates.有兩個因素影響行政,公共工程的估計的準確性。First,mostpublicagencieshaveconstraintsupontheirabilitytoawardconstructionprojectsbasedonthedifferencebetweentheengineer’sestimateandtheapparentlowbid.首先,大部分公共機構后,其施工能力,獎勵之間的工程師的估計以及差異明顯偏低的出價為基礎的項目的限制。Forinstance,theUtahDepartmentofTransportation(DOT)requirestheengineer’sestimatetobewithin10%ofthelowbid(UDOT).theOklahomaDOTishistoricallyrefrainsfromawardingtobidsthataremorethan7%overtheengineer’sestimate(ODOT),andtheU.S.ArmyCorpsofEngineer’s(USACE)hasmorelatitudebutisneverthelessconstrainedbythelowbidbeingnomorethan15and25%overtheindependentgovernmentestimateformilitaryandcivilworksprojects,respectively(USACE)1997.例如,猶她州運輸部(DOT)規(guī)定,工程師的估計將在10%低價中標(UDOT)。俄克拉荷馬DOT是歷史上從頒發(fā)給出價超過工程師的估計的7%的約束下(ODOT),以及美國陸軍工程師(美國陸軍工程兵團隊)有更大的自由,但還是由低是不超過投標限制15和25%以上的軍用和民用工程項目,分別為(美國陸軍工程兵團)1997年獨立的政府預算。Second,theissueisexacerbatedbymandatedmaximumprojectcontingencypercentages,whichlimitthemaximumamountofcontingencythatcanbeincludedintheagency’sengineerestimates.第二,加劇了該問題的應急計劃規(guī)定的最高比例,限制最高數(shù)額的應急可在該機構的估計數(shù)包括工程師。Forinstance,USACEislimitedto5%contingencyonnewconstructionprojects(USACE1997)andRiversideCountyCaliforniacannotexceed10%(RiversideCounty1999).例如,美國陸軍工程兵團限制為5％的應急新的建設項目(美國陸軍工程兵團1997年)和加利福尼亞州里弗賽德縣不能超過10％(河濱縣1999年)。TheUtahDOThasmoreflexibilityinsettingitscontingencyonaproject-by-projectbasisbut,mustjustifycontingenciesgreaterthan10%onprojectswithcompleteddesigns.猶她點有一個項目在設置上按項目的基礎上,但必須證明應急與完成的設計大于10％的項目其應急更大的靈活性。TheWashingtonDOTreportedthatthecostofhighwayconstructionwasup12.2%inApril(WSDOTa).華盛頓報道,交通部公路建設成本同比4月增長12.2％(WSDOTa)。SoprojectsawardedinRiversideCountywithits10%mandatedcontingencycapthatmonthwouldbeunderestimatedbyroughly2.2%.因此,在河濱縣授予其授權的應急上限,10月將是低估了約2.2％％的項目。Thesetwofactorscombinetocreateatendencytoinflateengineer’sestimatestoensurethatneededinfrastructureprojectsareawardableinperiodsofconstructionpricevolatility,andwhenthemaximuncontingencyisreached,toinflatetheestimatedquantitiesastheonlyavailableavenuetoincreasetheengineer’sestimate.這兩個因素結合起來,創(chuàng)造一種傾向,夸大工程師的估計來確保所需的基礎設施項目的建造價格波動周期,并當具有極大相關應急到達,夸大為唯一可用的途徑估計數(shù)量來提高工程師的估計。ThisfactwasconfirmedininformalsurveysconductedbytheprimaryauthorduringASCEcontinuingeducationclassesat10differentDOTs.這一事實證實了由主要作者進行非正式調(diào)查ASCE的過程中繼續(xù)在10個不同的交通部教育課。Whenaskedifquantitieswereeverinflatedtoincreaseprojectcontingencies,atleastoneengineerineachclassindicatedthatwasacommompractice.當被問及是否曾有充氣量增加項目突發(fā)事件,至少在每一類工程師表示,這是一個蒲公英的做法。Thispracticeisespeciallyproblematicinperiodsofextremevolatilitysuchseenforasphaltprices,inthefirsttwoquartersof(WSDOTa).這種做法,特別是在首兩季(WSDOTa)瀝青價格大幅波動的時期內(nèi)出現(xiàn)問題。Theverystructureoftheunitpricecontract’spricingmechanismdemandsengineer’sestimatedquantitiesbeasaccurateaspossibletoensuretheprofitabilityofabalancedbid.該單位的價格合同的定價機制,要求工程師的估計數(shù)量非常結構被認為是準確,最大限度地保證了均衡出價盈利能力。Whenactualquantitiesarelessthanthebidquantities,thecontractordoesnotrecoverthefixedcosts,overhead,andprofitthatwereallocatedtothequantitiesofworkthatwerenotinstalledandhenceforwhichitcannotbepaid.當實際數(shù)量比中標數(shù)量少,承包者不收回固定成本,開銷和利潤被分配給那些沒有工作的安裝,因此它不能用于支付數(shù)量。Therefore,asmostcontractorshavelimitedabilitytopickandchoosewhichprojectstheybidandremaininbusiness,inaccuratebidquantitiesleadtounbalancingunitpricestorecoverallthecostsassociatedwiththeprojectandtoprotectthecontractor’stargetprofitonthebid.因此,正如大多數(shù)承包商能力有限挑選哪些項目投標,并保持她們的業(yè)務,不準確的投標單位數(shù)量不平衡導致的價格收回所有與項目相關的成本,并保護承包人的出價的目標利潤。Theothersideofthatcoinistheuseofunbalancingtoincreasethecontractor’sprofitmargin.它的另一面是不平衡,增加承包商的利潤空間使用。Thesubjectofunbalancedbiddingiscertainlycontroversialandthepurposeofthispaperisnottoadvocateorapologizeforunbalancedbidding.不平衡的投標主體是一定爭議,本文的目的不是要提倡或道歉不平衡報價。Itistoadvocatethattheowner’sengineerresistthetemptationtoarbitrarilyincreaseaproject’sbidquantitiestocreateahiddenprojectcontingencyanddemonstratethepotentialimpactofdoingthatinonetypicalpublicagencybyananalysisoftheaccuracyofitsestimatingpractices.它是倡導,業(yè)主的工程師抗拒的誘惑,隨意增加項目的投標數(shù)量,以創(chuàng)立一個隱蔽工程的應急和證明這樣做的潛在影響,在一個典型的由一個做法,其估計精度分析公共機構。LumpSumCertainty:AbilitytoaccuratelysurveythequantityofworkCertaintyCostofError:ImpactUnitPriceoferroneousestimateatTimecontractaward.CostPlusCostofError確定性:能夠準確地調(diào)查工作的數(shù)量。成本誤差:在簽訂合同時錯誤估計的影響。一次性支付。單位價格。成本加。Fig.1.Contracttyperiskconcept-quantitycertaintyversuscostoferror圖.1、契約型風險概念的確定性與數(shù)量的錯誤成本。UnitPriceContracting單價承包?！盪nitpricecontractsareusedforworkwhereitisnotpossibletocalculatetheexactquantityofmaterialsthatwillberequired.Unitpricecontractsarecommonlyusedforheavy/highwaywork””優(yōu)惠價合同用于工作的地方是無法計算的材料的具體數(shù)量,這將是必須的。單價合同一般見于重型/高速公路的工作?！?SchexnayderandMayo).(施克斯納德和Mayo)。Whenanownerselectsunitpricecontracting,itisdoingsotosharetheriskofthefinalquantitiesofworkwiththecontractortoreducetheprice.當業(yè)主選擇單價承包,它這樣做,分享與承包商降價工作的最后數(shù)量的風險。Thishappensbecausethecontractordoesnothavetobidtheworstpossiblecaseifthequantitiesofworkarenotfiniteasitwouldbedriventodoinalumpsumcontractwhereitboretheentirequantityrisk.這是因為承包商沒有競投最壞的情況下,如果工作中的數(shù)量是有限的,因為這將不被趕做一筆合同在這里孕育了整個數(shù)量的風險。Unfortunately,manyownersdonotunderstandthedynamicsofunitpricebiddinganderroneouslybelievethatbypayingthecontractorforeveryinstalledunitofworkthattheyhavecoveredthecontractor’stotalcosts.不幸的是,很多業(yè)主不理解單價投標的動態(tài)和錯誤地認為,經(jīng)過支付各項工作,她們已經(jīng)討論了承包商的總成本安裝單位承辦。Thatonlyhappensinacost-pluscontactwheretheownerbearstheentirequantityrisk.這只會發(fā)生在成本加接觸的業(yè)主承擔全部數(shù)量的風險。Fig.1showstheconceptofwhendifferenttypesofcontractingmethodsshouldbeusedbasedontheowner’sabilitytoaccuratelyestimatethequantitiesofwork.圖.1顯示了在不同類型的承包方式,應采用基于業(yè)主能夠準確地估計工作的數(shù)量概念。Itshowsthatunitpricecontractsfallinthemiddlewhereneitherthelevelofcertaintynorthecostofanerroneousestimateishigh.結果表明,單價在合同中既不肯定也不是一個錯誤的估計成本高的水平下降。Thus,theriskisshared,andownersmustrecognizethatthecontractor’smajorunitpricingcontractriskisnotgettingtoinstallthetotalamountofworkuponwhichtheymustbid.因此,風險是共同的,業(yè)主必須認識到承包者的主要單位定價合約的風險是沒有得到安裝工作后,她們必須投標總量。Beforegettingintothemechanicsoftheunbalancedbid,onemustunderstandthefundamentalsofdevelopingaunitpriceforagivenworkitem.在深入的不平衡報價的機制得到,你必須理解為給定的開發(fā)工作項目單價的基礎。Essentially,aunitpriceisthesumofalldirectcosts,allocatedindirectcostsandthecontractor’sprofitforagivenitemofworkdividedbythetotalnumberofunitsofwork.從本質(zhì)上講,一個單位的價格是所有直接費用,間接費用分配和承包商的一個工作給予了工作單位的總數(shù)量除以項目的利潤總和。ThiscanbeexpressedasUP=(DC+IC+P)/N(1)這能夠表示為UP=(DC+IC+P)/N。WhereUP=unitprice;DC=directcost;IC=allocatedindirectcost;P=allocatedprofit;andN=numberofunits.UP=單價DC=直接成本;IC=分配間接費用;P值分配利潤;和N=單位數(shù)目。Thisequationrepresentsthemethodthatisrequiredbymanypublicagencyestimatingmanuals[(UDOT);RiversideCounty1999;(USACE1997)]andcanbetakenastheowner’sperspectiveonconstructioncostestimating.這個方程表示,是由許多公共機構所需的方法估算手冊[(UDOT);1999年河濱縣(美國陸軍工程兵團1997)],可作為業(yè)主的建筑成本估算的角度考慮。Carr(1989)definesdirectandindirectcostsasfollows:卡爾(1989)定義的直接和間接費用如下:Adirectcostofanactivityisphysicallytraceabletotheactivityinaneconomicmanner.以某活動的直接成本是可追溯至身體在一個經(jīng)濟的方式活動。Adirectcostisonenotcounted(accrued)iftheactivityisnotperformed.直接成本是不計(應計)如果不進行活動。Indirectcostsarebusinesscostsotherthandirectcostsofconstructionactivities;theyarenotphysicallytraceableandarecounted(accrued)eveniftheactivityisnotperformed.間接費用是經(jīng)營成本比其它施工活動的直接費用,她們是可追溯,并沒有物理計算(應計),即使不進行活動。Indirectcostsarealsoknownasoverhead.間接費用也稱為開銷。However,Constructioncontractorstendtousealesstheoreticalapproach,pragmaticallyseparatingcostsforunitpricecontractsintofixedandvariablecostsratherthandirectandindirectcosts(Carr1989).而建筑承包商傾向于使用較少的理論方法,務實分成固定費用和可變費用的單位價格為合同費用比直接和間接成本(卡爾1989年)。Thisresultsinadifferentwaytocalculatethesamenumberas這就導致了以不同的計算方式得出一樣的結果。UP=(FC+VC+P)/N(2)WhereFC=allocatedfixedcostandVC=variablecost.OnceagainCarrfurnishesasimplesetofdefinitionsthatareapplicabletothisapproach:FC=固定成本分配和VC=可變成本。再次卡爾furnishes的定義的種方法適用于簡單的設置:Ifacostchangesinproportiontoachangeinvolumeorquantity,itisvariable.如果在數(shù)量比例或數(shù)量變更費用的變動,它是可變的。Ifacostremainsunchangedintotal,despitewidefluctuationsinvolumeorquantity,itisfixed(Carr1989).如果成本維持不變,盡管在總數(shù)量上還是在數(shù)量大幅度波動,它是固定的(卡爾1989年)。Thereasonforthechangedperspectivehastodowiththedynamicsoftheunitpricecontractitself.為改變觀點的原因,是因為有單位價格合同本身的動態(tài)。Asthetotalvariablecostchangesproportionaltothenumberofunitsinstalled,thecontractorwillalwaysrecoveritsvariablecostsandthereforeitisnotatriskforthevariablecosts.由于總可變成本變化成比例的單位數(shù)目,安裝承包商將永遠收回其可變成本,因此,它不是在為可變成本的風險。However,thecontractorisatriskofnotrecoveringtheamountoffixedcostandtargetprofitthatithasallocatedforagivenworkitemifitdoesnotinstalltheengineer’sestimatedquantityofunitsuponwhichitwasrequiredtobid.然而,承辦商在未收回固定成本和目標利潤,它已經(jīng)為給定的工作項目,如果它不安裝工程師的后,它被要求投標單位的估計數(shù)量分配數(shù)額的風險。Conversely,ifthecontractorinstallsmorethanthebidquantityforthisitem,itwillrecoverthecompletefixedcostforthatitemonceithasinstalledthebidquantityandtheallocatedfixedcostwillbecomeawindfallprofitforthenumberunitsinstalledabovethebidquantity.相反,如果承包商安裝比此項目投標的數(shù)量更多,這將恢復該項目的完整的固定成本,一旦安裝了投標數(shù)量和分配的固定成本將成為暴利的數(shù)量單位安裝了上述出價數(shù)量。Therefore,itcanbeseenthatitislogicaltoaccountforcostsinamannerthatreflectstheriskinherenttocontract’spaymentmechanism.因此,能夠看出,這是合乎邏輯的方式,在一個固有的風險反映到合同的費用帳戶支付機制。Italsoallowsforamorepreciseaccountingforcostsbydirectlyassociatingdifferenttypesoffixedcostswithspecificworkitemsratherthanaccumulatingallindirectcostsandthenarbitrarilyallocatingthemtoworkitemsonapercentagebasis.它還允許一個由直接關聯(lián),而不是所有間接成本,積累與特定工作項目的不同類型的固定費用,然后分配給任意一個百分點的基礎工作,更精確的核算項目成本。Manypublicownersrecognizethecontractor’sriskofquantityunderrunaswellastheirownriskofquantityoverrunandprovideforrenegotiationofunitpriceforworkitemswhoseactualquantitiesvarymorethanagivenpercentageofthebidquantity(SchexnayderandMayo).許多公共業(yè)主認識到承包者的風險溢數(shù)量以及她們對自己的風險溢出數(shù)量,并提供工作項目的單位,其變化比投標數(shù)量(施克斯納德和Mayo)更實際數(shù)量一定比例的價格重新談判。Belowisalistoftypicalquantityvariationrangesaboveandbelowwhichtheagencywillallowthebidunitpricetoberenegotiated下面是一個典型的數(shù)量上面和下面該機構將允許投標單位的價格變化范圍進行重新談判的清單:·NewMexicoDOT:±20%(NMDOT)新墨西哥點:?！?0％(NMDOT);·OklahomaDOT:±25%(ODOT1999)俄克拉荷馬點:?！?5％(ODOT1999);·TexasDOT:±25%(TxDOT)德州點:?！?5％(TxDOT);·UtahDOT:±25%(UDOT)猶她州點:?！?5％(UDOT);·WestViurginiaDOT:±25%(WVDOT)西Viurginia點:?！?5％(WVDOT);and和·USACE:±15%(USACE1997).美國陸軍工程兵團:±15％(美國陸軍工程兵團1997年).Table1.BalancedBidExampleHot-mixasphalticconcrete(HMAC)payitemUnitpriceelementDescriptionTotalcostBidquantityUnitcostVariablecostMaterials,labor,andequipment$3.85M50Kt$77/tFixedcostsMobilize/demobilizeplantandequipment$250K50Kt$5/tAllocatedoverhead,financing,etc.$300K50Kt$6/tTargetprofit$100K50Kt$2/tFinalbidtotals$4.5M50Kt$90/tOtheragencies,suchastheAlaskaDOT,(ADOT&PF),donotcontainsuchclausesintheirunitpricecontracts.其它機構,例如阿拉斯加的DOT(ADOT及公積金),不包含在她們的單位價格合同等條款。Thiscreatesasituationwheretheriskofunderrunquantitiesisunboundedandthereforeincreased.這將創(chuàng)立一個凡欠載量的風險是無限的,因此增加的情況。Byincludingaunitpriceadjustmentclause,theownerislimitingbothitsownandthecontractor’squantityvariationrisk.經(jīng)過包括單位價格調(diào)整條款,業(yè)主是其本身的限制和承包商的數(shù)量變化的風險。Thisissueisbestillustratedbyexample.Table1showsthecontractor’sestimateforapavementworkitemonastateprojectwheretheunitpriceadjustmentclauseallowsavariation±20%beforetheunitpricecanberenegotiated.這個問題是最好的說明例子。表1顯示了承包商對項目上的路面狀態(tài)估計那里的工作項目單價調(diào)整條款允許變化±20％的單位之前的價格能夠重新談判Onecanseethatthecontractorchosetoassociatethecostofmobilizinganddemobilizingtheasphaltbatchplantandassociatedequipmentwiththisparticularworkitem.人們能夠看到,選擇承包商聯(lián)營調(diào)動和遣散的瀝青攪拌站的費用以及與此特定的工作項目相關的設備。Additionally,aproportionalamountoftheoverheadandothergeneralfixedcostsandtargetprofitwasalsoallocatedtothisitem.另外,間接費用和其它一般固定費用和目標利潤總額的比例也分配給這個項目。Thus,theunitpriceof$90.00pertonisabalancedunitprice.因此,每噸90.00美元的單價是一個平衡的單位價格。FromTable1,onecandevelopanalgebraicformulatocalculatethecontractor’scostfortheactualnumberofunitsinstalled從表1,能夠建立一個代數(shù)公式來計算的單位實際安裝的數(shù)量承包商的成本。Actualcost=TotalFC+VC(N).實際成本=總界別+創(chuàng)投(N)的。TheOhioDOT()takesthisastepfartherbyquantifyingamathematicallyunbalancedbidbyrequiring:”Biddersmustbidatleastthecostofthematerialsforeveryitembid.”TheTexasDOTregulations(TxDOT)agreewithbothOklahonmaandNhio’sinterpretations.TxDOT’sspecificationsinconcertwithfederalregulation23CFR635.114(CFR)goontostatethatacontractmaybeawardedtoamathematicallyunbalancedbidbutmustrejectamateriallyunbalancedbid.TxDOTpointsouttwosituationsinwhichmaterialunbalancingarefound:·”Thereisanerrorin[theengineer’sestimatedbid]quantities(toolow)andthecontractorbidsahighpriceontheseitems.Inthiscase,theapparentlowbiddermightnotbetheactuallowbidderoncethequantityerroriscorrected.”·Thecontractor’sbidpricesarehighonitemsofworkoccurringearlyintheproject.Inthiscase,theapparentlowbiddermightnotbetheactuallowbidderwhentheState’sfinanciallossofpotentialinterestincomeiscalculated(TxDOT).ThesecondTxDOTdefinitionreferstoasituationthatiscommonlycalled”front-loading”(SchexnayderandMayo).Front-loadingcanbecomeaformofmathematicalormaterialunbalancing.Front-loadingisdonetogenerateadditionalcashflowintheearlyphasesoftheproject(MayerandDeikmann1982).Asthisissueisnotcreatedbytheengineerwhodevelopsthebidquantitiesonaunitpricecontract,itisbeyondthescopeofthisstudy.Therefore,thepaperwillrestrictitselftoevaluatingunbalancingonlyandmakenoefforttoidentifypotentialfront-loadinginthesamplepopulation.AllthreestateDOTscitedaboveareallowedtoawardcontractstomathematicallyunbalancedbidsandmustrejectmateriallyunbalancedbids.Thus,itcanbeconcludedthatmathematicalunbalancingisanexpectedpracticeduetothepossibilitiesoferrorsintheengineer’sestimatedbidquantities,andthatatleastthesethreeagenciesseemathematicalunbalancingasanecessarypartofunitpricecontracting.However,materiallyunbalancingabidisdeemeddetrimentalwhenitappearsthatitwillultimatelyresultinfinalcostthatcausestheagencytopaymorethatitwouldhavepaidifthebidhadbeenbalanced.Theabovediscussionleadstotheinferencethattheethicallinehasbeencrossedwhenaunitpriceismateriallyunbalanced,i.e,bidatapricethatislowerthanitsvariablecost.Therefore,itisimportantthatengineersandconstructioncontractorsbothunderstandanddifferentiatebetweenmathematicalandmaterialunbalancing.Tosummarizethissectionandmoveontotheresearchaboutwhichthispaperisfocused,anownerthatoptstouseunitpricecontractingislayingthefoundationformathematicallyunbalancedbids.”Unitpricecontractstendtodrawunbalancedbidding(Zack).”Tominimizetheowner’srisk,itmuststrivetofurnishanaccuratesetofbidquantities.Roberts(1994)putitthisway:”Iftheownerdesiresareasonablybalancedbid,thenalleffortmustbemadetoprovidethefollowing:anequitablemobilizationpayiteminthebid,realisticbidquantities;andachangedquantityclanseinthespecifications.”The”equitablemobilizationpayitem”speakstotheneedforearlycashflowtominimizecarryingcosts.”Realisticbidquantities”meansdiligentlycompletinganaccuratequantityestimateuponwhichtobasethebidquantitiesofwork,andthe”changedquantityclause”isamechanismtobindtheriskofquantityvariationsbypermittingarenegotiationofunitpricesasactualquantitiesofworksignificantlyvarywiththebidquantities.Mostpublicagencyunitpricecontractscontainthesethreeitems.Sothepointwherethesystemcanbreakdowniswhenanengineerdecidestoalterthebidquantitiesfromthosedeterminedintheaccuratequantityestimatetobuildanadditionalcontingencyintheprojecttoguardagainstconstructionpricevolatility.Whenthisoccurs,theengineerisdeliberatelycreatingaquantityunderrun,whichinturnforcestheconstructioncommunitytounbalancetheirunitpricestoprotecttheirfixedcostsandtargetprofit.ObjectiveandMethodologyTheobjectiveoftheresearchwastoevaluatethebidquantitiesgeneratedforOklahomaDOT(ODOT)engineers’estimates,determiningiftheagencyisunintentionallytriggeringunbalancedbiddingduetoinaccuratebidquantities.Theresearchmethodologywassimple.First,alargesampleof462constructionprojectscompletedovera4yearperiodfromalleightofODOT’sdivisionswascollectedfromtheagency’sAASHTOSiteManagerdatabase.(AASHTO)ODOThasover5,500separatepayitems.Theestimatingerrorsofinteresttothisresearcharetheonesthatoccurinpayitemswhereitispossibletoinduceinflatedfinalquantitiesthroughrounding,estimatingassumptions,anddouble-counting.Otherissues,suchasitemsthatarescheduledependent,weredroppedfromtheanalysis.Thus,thepayitemsthathadunitsof”lumpsum,””each,””day,””signday,”etc.wereremoved,Next,payitemsthatwereadministrativeinnaturesuchas”railroadflagging,””asphaltbinderadjustment,”and”mowing”werealsoremoved,Finally,ancillarypayitemslike”watering”and”temporarysiltdike”werealsodropped,Theobjectivewastofilterthepossiblepayitemsdowntothosethataredirectlyrelatedtotheproject’stechnicaldesignanddrivetheengineer’sestimatedquantitiesofwork.Thepercentageoferrorforeachpayitemwascomputedusingthefollowingformula:缺一段,有公式不會打Next,payitemsweregroupedintosixcommodity-basedcategoriestoidentifysystemicerrorsinestimatingthequantitiesofspecifictypesofwork,.Forexample,”Portlandcementconcrete”measuredbythesquareyardhas12differentpayitemsvaryingbythickness.Theestimatingtaskhereistodeterminethetotalnumberofsquareyardsofthismaterial,Therefore,apossiblesystemicerrorwouldrelatetoassumptionsmadebytheengineertocalculatetheareaofirregularshapesandaprojectwithalargenumberofirregularshapes(i.e.,driveways,intersectionradii,gores,etc.)wouldhaveagreaterpotentialforerroneousquantitiesthanonethatwasprimarilymainlanepaving,Theaverageerrorforeachcommoditygroupwascalculated,andthentheoutputwasrankedfromgreatesttoleasterror,Finally,thefocustheanalysistoamanageablelevel,thesixpayitemsshowninTable3thathadthegreatesterrorinitscategorywereselectedforin-depthanalysisbyODOTDivision,NotethatanDODTdivisionistheorganizationallevelatwhichplansarepreparedandconstructioncontractsareawardedandadministered.Table3.AnalysisofErrorinSixODOTPayItemsSolidslabsoderrorTrafficboundsurfacecourseerrorColdmillingerrorAverageAbsoluteAverageAbsoluteAverageAbsoluteDivision(%)(%)(%)(%)(%)(%)110.7419.03-3.2438.72-9.4412.82217.0024.18-9.5224.28-7.8025.0734.5426.27-4.7224.85-2.4829.784-17.8633.799.1214.873.5717.83519.2923.90-0.300.30-13.4515.1962.1917.801.072.97-11.2511.257-11.5824.38-14.0717.323.1014.3082.2725.34-2.4321.87-33.9033.98ODOT3.3224.34-3.0118.15-8.9520.03AsphaltserrorTackcoaterrorPorlandcementconcretepavingerrorAverageAbsoluteAverageAbsoluteAverageAbsoluteDivision(%)(%)(%)(%)(%)(%)1-4.0513.50-13.3123.2828.8739.932-2.1210.08-6.3218.88-6.3917.343-0.1010.58-13.2223.1015.7216.6841.8612.47-16.4823.105.1714.1654.566.86-33.9633.96NoneNone6-0.201.26-32.5832.58-0.942.147-2.8810.38-55.8355.838.399.7483.1412.08-16.2316.234.9715.15ODOT0.039.65-23.4928.377.9716.45Thein-depthanalysisofquantityestimatingerrorwasperformedattwoleves.First,theerrorinthesixpayitemsofinterestwasassessedbyODOTDivision.Thepurposeofthisanalysiswastodetermineifindividualdivisiondesigngroupshadissuesestimatingthequantitiesofagivenitem.Thedivision-by-divisionanalysisalsoreflectsdesignandconstructionpreferencesthatmaynotbeareflectionofthestate-wideapproach.Thesecondlevelwastoroll-upthedivisionerrorsandcalculateastatelevelerrorforeachofthesixpayitems.ThiswasdonetoassessquantityestimatingissuesacrossthestateandreflectODOTdesignandconstructionpolicy.Finally,thepayitemerrorswereevaluatedonanaverageerrorandabsoluteerrorbasis.Theaverageerrorismerelythemathematicalaverageofalltheerrorsinthesample.Theabsoluteerroraccumulatedthesampleerrorwithoutregardtosign.Forexample,theaverageerrorforanitemthathadoneprojectwitha50%overrunandanotherprojectwitha50%underrunwouldbe0,indicatingthattheengineer’sestimatedquantitieswereperfectwheninfactthereisaseriousproblem.Theabsoluteerrorforthesametwo-projectsampleis50%andaccuratelyreflectstheactualestimatingissue.Theabsoluteerroralsomorecloselyreflectstheunbalancingissuebecausecontractorswillunbalancepayitemunitpricestoaccountforbothoverruns.Therefore,theinferencecanbemadethatahighabsoluteerrorinapayitemcorrelatestoahighprobabilityoftriggeringunbalancedunitpricing.So,anagencylikeODOTcouldhavealowlevelofcostgrowthduetoquantityoverrunsandstillhaveanestimatingproblembecausethelowcostgrowthisarrivedatviacompensatingerrors.ResultsoftheResearchTable3showsthatquantityestimatingerrorsaregreatestinthetackcoatpayitemwiththreeofeightdivisionsexperiencinganaverageerrorof>25%whichisthepointwhereODOTspecificationspermitarenegotiationofpayitemunitprice.Thisinfersthatthesethreedivisionswillneedtorenegotiatetheunitpriceoftackcoatmoreoftenthantherestofthedivisioninthestate.Additionally,inalldivisionswheretheaverageerrorisnegativeindicatinganunderrun(i.e.,theengineeroverestimatedthequantitysothecontractorinstallfewerunitsthanthenumberthebidquantity).Fromastandpointoftriggeringcontractorunbalancing,underrunningthebidquantityisthemoredangerousofthetwoerrors.Whilethestudydidnothaveaccesstocontractorb