建筑專業(yè)畢業(yè)設(shè)計外文翻譯--公路建設(shè)造價的未來

1、<p><b>　　中文5358字</b></p><p><b>　　2725單詞</b></p><p>　　本 科 生 畢 業(yè) 設(shè) 計（論文）</p><p><b>　　外文翻譯</b></p><p>　　題目Ⅰ：Estimating Future High

2、way Construction Costs</p><p>　　來源：C. G. Wilmot, M.ASCE, and G. Cheng, P.E．Estimating Future Highway Construction Costs．JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT © ASCE / MAY/JUNE 2003：272—279&

3、lt;/p><p>　　Estimating Future Highway Construction Costs</p><p>　　C. G. Wilmot, M.ASCE,1 and G. Cheng, P.E.2</p><p>　　Abstract: The objective of this research was to develop a model th

4、at estimates future highway construction costs in Louisiana. The model describes overall highway construction cost in terms of a highway construction cost index. The index is a composite measure of the cost of constructi

5、on labor, materials, and equipment; the characteristics of contracts; and the environment in which contracts are let. Future construction costs are described in terms of predicted index values based on forecasts of</p

6、><p>　　Key words: Highway construction; Costs; Estimation.</p><p>　　Introduction</p><p>　　State Departments of Transportation are required to prepare highway construction programs that

7、 describe their planned construction activity in the short term. There is usually considerable interest in the program from local authorities, politicians, and interest groups. Draft programs are typically presented to t

8、he public and to various agencies at the local, regional, state, and federal level for comment and review. Ultimately, a program will be approved by the state legislature and will become</p><p>　　Because ind

9、ividual projects are of considerable importance to politicians and individual interest groups, it is common that progress on a construction program is closely monitored. Any deviation is likely to be queried, and the Sec

10、retary of the state Department of Transportation or a senior official in the department will often have to defend the situation publicly or in the state legislature. This can lead to perceptions of incompetence and erosi

11、on of support from the legislature and the public</p><p>　　To prepare reliable highway construction programs, road authorities must have accurate estimates of future funding and project costs. While future f

12、unding is obviously never known witha great deal of certainty, it is often the estimation of project costs that cause upsets in the execution of construction programs. Inaccurate cost estimation is one source of error, b

13、ut another, the escalation in cost of a project over time, is another source disruption to the program that is usually not anticipat</p><p>　　Measuring Project Costs</p><p>　　When construction i

14、n the field lags behind planned construction in the construction program, it is usually because the projects that have been constructed have cost more than anticipated. This is not random variation of actual costs about

15、estimated costs, because, clearly, underestimates would cancel out overestimates over time in such a situation. Rather, it is evidence of a consistent underestimateof all projects collectively. The benefit of this is tha

16、t it can be measured at the overall level</p><p>　　In the past, change in overall construction costs has been measured in terms of construction indices. These indices are weighted averages of the cost of a s

17、et of representative pay items over time. They have been used to display cost trends in the past. However, there is no reason why cost indices must be restricted to displaying past trends; they can also portray future ov

18、erall costs, provided the representative pay items on which the index is based can be forecast. A predictive construction co</p><p>　　Past Increases in Construction Costs</p><p>　　When the chang

19、e in overall construction costs in the past is observed（as measured by popular construction cost indices）, it is apparent that they change significantly from year to year and that the changes can sometimes be quite errat

20、ic. The common assumption that construction costs change with the rate of inflation can lead to poor estimates of future construction cost. To illustrate, the Federal Highway Administration’s Composite Bid Price Index, a

21、n index of overall highway construction costs,</p><p>　　Past Methods of Forecasting Highway Construction Cost</p><p>　　Forecasting future highway construction costs has been achieved in basicall

22、y three ways in the past. First, unit rates of construction such as dollars per mile by highway type have been used to estimate construction costs in the short term. However, this method has generally been found to be un

23、reliable, because site conditions such as topography, in situ soil, land prices, environment, and traffic loads vary sufficiently from location to location to make average prices inaccurate estimates of th</p><

24、;p>　　Second, extrapolation of past trends, or time-series analysis, has been used to forecast future overall construction costs （Koppula 1981; Hartgen et al. 1997）. Typically, construction costs have been collapsed in

25、 these analyses to a single overall expression of constructioncost such as the FHWA CBPI or the Engineering News Record’s Building Construction Index ~ENR BCI! or Construction Cost Index ~ENR CCI!. However, these types o

26、f models are usually only used for short-term forecasting due to the</p><p>　　Third, models have been established that describe construction costs as a function of factors believed to influence construction

27、costs. The relationship between construction costs and these factors have been established from past records of construction costs. Typically, the models established in this manner have been used to estimate the cost of

28、individual contracts. These models, with their relational structure, are the only models expected to provide reliable long-term estimates. The model de</p><p>　　Proposed Construction Cost Model</p>&l

29、t;p>　　It is clear that there are numerous factors that affect construction costs. However, it is striking that most construction cost models developed in the past have used only a few of the many influential factors i

30、dentified above. One reason for this is that information is generally not available on many factors in data sets used to estimate models. Another reason is that information on the qualitative conditions surrounding each

31、contract is difficult to obtain. These are problems that prevail in m</p><p>　　To mitigate against the effect of an incomplete set of factors, two strategies can be employed. First, it may be possible to rep

32、resent some of the absent factors by surrogate variables that are in the data set. For example, as mentioned earlier, annual bid volume has been used in the past as an inverse measure of the level of competition prevaili

33、ng in the construction industry at that time （Herbsman 1986）. Similarly, the number of plan changes each year can serve as a measure of design quality. </p><p>　　The objective of this study is to establish a

34、 model, estimated on historical quantitative data, that incorporates as many relevant variables as possible and is capable of estimating the future overall cost of highway construction on an annual basis. The model is in

35、tended to assess the impact of alternative future conditions on highway construction costs and assist officials of the Louisiana DOTD to identify management policies that will help limit the increase in highway construct

36、ion costs in th</p><p>　　It was also the perception of those interviewed that contracts let in the fourth quarter of the fiscal year tended to result in higher bid prices. This was because there was a tenden

37、cy for projects to accumulate in the fourth quarter due to various delays, and the increased volume of projects resulted in decreased competition among contractors.</p><p>　　Model Structure</p><p&

38、gt;　　The model developed to predict overall highway construction costs in this study is based on five submodels of price estimation. Each submodel estimates the price of a pay item representative of cost model a dominant

39、 construction area. Dominant construction areas were identified from past expenditure in different areas of highway construction. From the Louisiana DOTD data for the period1984–1997, it was found that more than 50% of a

40、ll highway construction expenditure occurred in the areas of asph</p><p>　　A schematic representation of the overall model with its five submodels is shown in Fig. 2. Each submodel estimates the price of a r

41、epresentative pay item from each of the five dominant construction areas. The contribution of each submodel to the overall model is accomplished by combining the prices of the representative pay items in an index similar

42、 to that of the FHWA CBPI. In this case, because the formulation is slightly different from the FHWA CBPI and is constructed specifically to reflect</p><p>　　Validation</p><p>　　Model performanc

43、e is ideally validated using data not used in the estimation of the model. In this case no such data was available. Dividing the existing data set into two portions to estimate the model on one portion and use the other

44、for validation was not practical, given the limited sample size in some of the submodels. For example, the concrete pavement submodel has a total of only 212 observations, and estimating the submodel on the highly variab

45、le data on fewer observations would reduce t</p><p>　　Using the same data as that on which the model was calibrated, the estimated and observed LHCI values for the period 1984–1997 are shown in Fig. 3. The 9

46、5% confidence limit of the observed LHCI is also shown in the figure to illustrate that the estimated LHCI values are, for the most part, contained within the 95% confidence limit of the observed LHCI values. The chisqua

47、red test of the similarity of the estimated and observed LHCI values indicates that a significant difference could not be obser</p><p>　　Investigating the behavior of the construction cost index in Fig. 3 re

48、veals interesting reasons behind the observed behavior. Reviewing the data and observing its impact on the forecasts through the model allows an analyst to determine the primary causes of change in construction costs dur

49、ing certain periods in the past. For example, the main cause of the decrease in construction costs observed in the period 1984–1986 can be traced back to a decline in labor and petroleum costs during that perio</p>

50、<p>　　Conclusions</p><p>　　This study has shown that the literature indicates that a comprehensive set of factors contributes to the cost of highway construction. In this study, the most influential f

51、actors were found to be the cost of the material, labor, and equipment used in constructing the facility. However, characteristics of individual contracts and the contracting environment in which contracts are let also a

52、ffect construction costs. In particular, contract size, duration, location, and the quarter in which the co</p><p>　　The model developed in this study reproduces past overall construction costs reasonably ac

53、curately at the aggregate level. Predicted overall construction costs are not significantly different from observed costs at the 99% level of significance. This accuracy is largely the result of the aggregate level at wh

54、ich construction costs are measured in this study; at the individual contract level, the submodels capture only between 42 and 72% of the variation in the data. It is suspected that much of </p><p>　　This mo

55、del can be used by highway officials in Louisiana to test alternative contract management strategies. Increasing contract sizes, reducing the duration of contracts, reducing bid volume and bid volume variance, reducing t

56、he number of plan changes, and reducing the proportion of contracts let in the fourth quarter all serve to reduce overall construction costs. Highway officials can assess the impact of strategies they believe are achieva

57、ble by applying the model. Most importantly, though, </p><p><b>　　Reference</b></p><p>　　Associate Professor, Louisiana Transportation Research Center and Dept. of Civil and Environm

58、ental Engineering, Louisiana State Univ., Baton Rouge, LA 70803-6405.</p><p>　　Civil Engineer, GEC, Inc., 9357 Interline Ave., Baton Rouge, LA 70809. </p><p>　　C. G. Wilmot, M.ASCE, and G. Cheng

59、, P.E．Estimating Future Highway Construction Costs．JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT © ASCE / MAY/JUNE 2003：272—279</p><p>　　Huyn P.N., Geneserth M.R. and Letsinger R. (1993). ‘Automate

60、d concurrent engineering in design’. World Computing, Vol. 26 (1), pp 74–76. </p><p>　　ISO (1994). ISO 10303-1 Part 1: Overview and fundamental principles, International Organization for Standardization, Gen

61、eva, Switzerland. </p><p>　　Kalay Y.E., Khemluni L. and Choi J.W. (1998). ‘An integrated model to support distributed collaborative design of buildings’. Automation in Construction, Vol. 7 (2–3), pp 177–188.

62、 </p><p>　　Lee H.K., Lee Y.S., Kim K.H. and Kim J.J. (2007). ‘A cost-based information model for an interior design in a large-scale housing project’, ICCIT 07, 2007 International Conference on Convergence I

63、nformation Technology, Poster Sessions: Session 4.</p><p>　　Luiten G.T.B. and Tolman F.P. (1997). ‘Automating communication, in civil engineering’. Journal of Construction Engineering and Management, Vol. 12

64、3 (2), pp 113-120.</p><p><b>　　公路建設(shè)造價的未來</b></p><p>　　C. G. Wilmot, M.ASCE,1 and G. Cheng, P.E.2</p><p>　　1聯(lián)合教授，路易斯安娜運輸研究中心和國家環(huán)境工程局，路易斯安娜國立大學</p><p><b&g

65、t;　　2注冊工程師</b></p><p>　　摘要：本文的目標是建立一個用來估算路易斯安娜未來公路建設(shè)所需的工程費用的模型。根據(jù)公路建設(shè)造價索引，該模型介紹了中所有公路建設(shè)的工程費用。這索引是一份綜合定額，包括建造的人工費，材料費和機械費，項目特征和項目周邊的環(huán)境情況等等。未來工程的費用是用預計值來進行指定的，預計值是建立在建造人工費，材料費，機械費和預見項目特征和項目環(huán)境基礎(chǔ)上的預測價格。在公路

66、管理機構(gòu)控制下的項目特征和項目環(huán)境能可根據(jù)未來的成本削減政策來操作處理。公路造價預算模型在路易斯安娜的運用表現(xiàn)出這模型幾乎是1984—1997年時建設(shè)造價模型的重現(xiàn)。未來在運用公路造價預算時，該模型預測路易斯安娜的公路造價將在1998年到2015年間的增加兩倍。在應用削減成本政策和假設(shè)投入的資金比預算減少20%的情況下，模型預測公路造價將在1998年到2015年間提高75%。</p><p>　　關(guān)鍵詞：公路建設(shè)

67、，造價，預算</p><p><b>　　引言</b></p><p>　　國家交通部被要求籌備能反映他們短期建設(shè)計劃的公路建設(shè)綱要。通常地方當局，政治家和利益集團都會對此項目投以極大的關(guān)注。草案一般會向社會、地方、省、國家各部門和標準聯(lián)合會征求意見和建議。最后，項目將由國家立法機關(guān)批準，在一段時間后的下一輪新項目立項中成為國家交通部的正式建設(shè)項目。</p>

68、;<p>　　因為特殊項目對于政治家和個別利益集團是非常重要的，通常要對工程過程進行監(jiān)理。任何偏差都有可能被質(zhì)疑，國家交通部長和資深官員將不得不公開或找國家立法機構(gòu)對情況進行辯護。這會導致使人不相信你的能力，并使來自立法機構(gòu)和公眾的支持受到?jīng)_擊。</p><p>　　籌備可靠的公路建設(shè)項目，公路管理機構(gòu)必須對預留資金和工程造價有精確的評估。然而很明顯，預留資金永遠不能確保，通常是對在建設(shè)項目實施中引

69、起混亂的項目造價的評估。不準確的造價意見是一個錯誤來源，但另一方面，不斷過時的工程造價是另一個使項目失敗的原因，這些通常沒有預料和準備，一般，工程造價是根據(jù)一系列現(xiàn)在的工程造價判斷的，如果不符，完工時進行調(diào)整。造價增加是有效的，當然是漸增的，而且，他們每年按一定比例增加。本文的核心是估計未來公路建設(shè)。本研究中模型建立的資料來自路易斯安娜交通和發(fā)展部（DOTD），是特別針對這個州的。然后，這種方法可在其他領(lǐng)域使用。</p>

70、<p><b>　　項目造價估量</b></p><p>　　當某領(lǐng)域建設(shè)落后于建設(shè)計劃中的進度，通常是因為已經(jīng)建造的項目費超過了預期費用。實際費用相對于預算不是隨意變動的，因為很明顯在這種情況下過低估計與過高估計會相互抵消。而且，這是所有項目全部過低評價的證據(jù)。這樣的好處是能在一般水平估量，這比在特別的項目水平估量容易得多。</p><p>　　過去，在一

71、般建設(shè)造價中的變化已經(jīng)測量在一系列建設(shè)索引中。這些索引不斷加入一些典型費用項目的平均造價。他們已經(jīng)習慣于根據(jù)過去造價。但是無法解釋造價索引必須嚴格表現(xiàn)過去趨勢的原因，他們同樣能表現(xiàn)未來一般造價，預備建立索引的典型費用項目，能預測。預算造價索引在本研究中被用于解釋未來在一般建設(shè)造價的變化。索引的簡化公式會在下文中提到。</p><p><b>　　建設(shè)造價的增長歷史</b></p>

72、<p>　　當過去一般建設(shè)造價中的變化被注意到了（如被普通建設(shè)造價索引估量），很明顯這年復一年變化得很顯注而且有時非常沒規(guī)律。通常建設(shè)造價隨通貨膨脹率變化的設(shè)想會對未來建設(shè)造價做出錯誤的判斷。舉個例子，公路管理聯(lián)合會（FHWA CBPI）的綜合投標價格索引是關(guān)于一般公路造價的索引，如圖1和用戶索引（CPI），是通貨膨脹的通常表達。FHWA CBPI中區(qū)分為對于整個國家和只對路易斯安娜。所有索引已經(jīng)因相似目的在1987年根據(jù)

73、100標準規(guī)范。從表中清楚看到公路建設(shè)造價變化不規(guī)律，甚至呈現(xiàn)趨向于CPI變化的不同長短期。而且很明顯建設(shè)造價變化在路易斯安娜和整個國家是不同的。沒有在此顯示的，其他國家FHWA CBPI的評論表明其中一些與國家標準有偏差。</p><p>　　過去公路建設(shè)預算方法</p><p>　　公路建設(shè)未來造價已經(jīng)基本上形成了三種方法。第一種，如美元一樣，不同類型公路每公里單位建設(shè)價格已經(jīng)用于短期

74、預算（Hartgen and Talvitie 1995；Stevens 1995）。但是經(jīng)常發(fā)現(xiàn)這種方法不穩(wěn)定，因為像地貌等場地情況，土壤，土地價格，環(huán)境和交通在地區(qū)間用平均價格對特殊工程，甚至對特殊年份的所有工程進行不準確造價有很大差異（Hartgen and Talvitie 1995）。第二中，通過對過去趨勢推斷或時間段分析進行一般建設(shè)預算（Koppula 1981；Hartgen et al.1997）。通常，建設(shè)造價在僅對一

75、般造價描寫的分析中已失去意義，如FHWA CBPI，工程新紀錄之建筑工程定額（ENR BCI），或建設(shè)造價定額（ENT CCI）。但是，這些模型通常只用于短期預算，因為他們相信國家一定會保持過去的狀態(tài)。第三種模型已經(jīng)確立，這把建設(shè)造價描述為影響造價的功能因素。建設(shè)造價和這些因素之間的關(guān)系已經(jīng)從過去的建設(shè)造價紀錄中確定。通常這樣確定的模型已經(jīng)用于判斷特殊項目的造價。這些模型和其關(guān)系結(jié)構(gòu)是用于提供不規(guī)律長期判斷的唯一模型。本研究中就是這個模

76、型。</p><p>　　著作表明很多因素影響建設(shè)價格。一項在紐芬蘭，Hegazy和Ayed（1998）的研究發(fā)現(xiàn)季節(jié)、地點、工程類型、項目持續(xù)時間和項目規(guī)模對單個項目造價有重大影響。Herbsman(1986)表示，除材料費，人工費和機械費，每年的項目總量（i.e.,the so-called bid volume）影響項目價格。這是智慧的提議，價位影響競爭（至少在短期內(nèi)），反過來，這也影響項目價格。Olsen

77、和Epps（1981）表示出價量年復一年的變化影響出價價格。其他人認為政府法令，計劃變動，承造方管理團隊的質(zhì)量，提高竣工安全及時間的項目信息對建筑造價有影響（Koehn et al.1987;Elhag and Boussebaine 1998）.也有人說質(zhì)量因素，如建造企業(yè)的表里如一，建造者的需求，以及建造者與管理機構(gòu)的關(guān)系都會對建造有很大影響（Fayek 1998）。</p><p><b>　　建

78、設(shè)造價模型</b></p><p>　　很顯然有很多因素影響造價。然而令人吃驚的是過去大部分造價模型只用了一小部分重要因素控制造價。一個原因是通常沒有關(guān)于很多因素資料的可用信息去評價模型。另一個原因是關(guān)于每個項目質(zhì)量情況的信息很難獲得，在大多數(shù)情況下成功和很難克服都是問題。</p><p>　　我們能用兩種策略來減輕不良因素的影響。首先，可用資料集中可變因替代潛藏因素。舉個例子

79、，如早先提到的，過去每年的出價規(guī)?？勺鳛樵u價那時建設(shè)產(chǎn)業(yè)競爭力水平的反因子（Herbsman 1986）。同樣的，每年計劃的改變量能評價設(shè)計質(zhì)量。其次，如果建設(shè)造價模型每年從評價特殊模型到一般項目造價的變化，這樣能簡化模型化工作。這是因為不需要為那些價格隨情況變化的個案建立模型，因為這情況也會在同年消失。舉個例子，降低出價而獲勝的企業(yè)會在同一年以因此提價來達到平衡，因為他們已經(jīng)做了足夠的工作而且不急于求成。同樣的，那些有建筑需求技術(shù)的企

80、業(yè)和低水平技術(shù)企業(yè)在這領(lǐng)域達到平衡。因此，通常用更少的因素在整體水平比在處于崩潰水平建立模型更好。</p><p>　　本研究的目標是在評價相當數(shù)量歷史材料的基礎(chǔ)上建立一個模型，這些材料集合了盡可能多樣的材料，而且在每年基礎(chǔ)上能評定出未來公路建設(shè)的總體造價。這模型將用于評價未來不同情況對公路造價的影響，能促進路易斯安娜DOTD政府統(tǒng)一對那些能在為倆幫助控制本國公路造價增長的警務的管理。</p>&l

81、t;p><b>　　資料</b></p><p>　　這是從路易斯安娜DOTD獲得了1984-1997年間的公路建設(shè)項目資料，由2827份公路和橋梁項目的信息組成，包括項目價格、建造類型、設(shè)備功能、租金日期、項目持續(xù)時間、地點和在項目開始和結(jié)束間的持續(xù)時間和價格中的任何改變。信息在子項目中同樣有用。單個項目要準備119，607份關(guān)于項目文本、價格、測量單元、數(shù)量和在施工中價格和質(zhì)量的任

82、何變化的信息。項目書及其變動和每年計劃改變的總數(shù)都是從原始資料中獲得的。</p><p>　　項目見面會有三個設(shè)計師主持，他們至少在資料涉及的時期內(nèi)在路易斯安娜DOTD服務，一次是面談，另兩次通過電話會議交談。面試官有一份問題單去控制面試，但回答人也可選擇回答范圍。這會確認實施中的變化，如更堅硬的道路設(shè)計能容納更多交通量，欄桿下鋪磚便于除草，注意沖蝕控制，欄桿末端處理變化，增加臨時交通線的用處。不管怎樣，因為這些

83、變化是在分析階段逐漸出現(xiàn)的，經(jīng)常兩個完工項目會部分重疊，所以不可能判斷實施中個別變化的影響。另一方面，一項對于瀝青水泥項目設(shè)計書的改變在1992年被制定，鑒于那些會談，這對以后瀝青水泥的出價增長立即負起了責任。變化包括聚合改性瀝青的介紹和提高材料種類測試程序的應用。這些變化是所期待的，同時也推廣使提高瀝青水泥的造價大約12%。</p><p>　　會談洞察到項目承包在四分之一財務年中會使報價更高。因為有一個趨勢是

84、在四分之一年中會積累各種障礙，工程量的提高會減少承造者間的競爭。</p><p>　　關(guān)于過去和未來建設(shè)資金的資料是從多種來源獲得的。貿(mào)易局的經(jīng)濟研究處公布了工業(yè)雇傭和收入的歷史記錄，用來評價每個工業(yè)部門的工人人均工資。這個信息用來確定1980-1997年間建筑從業(yè)者的平均年薪資。BEA還推測出了未來工業(yè)雇傭和工資情況，這對預測建筑工人薪資提供信息。1987年過去和預測的工人薪資水平被編成了一份反映每100勞動力

85、價值的統(tǒng)計表。1984-2015年間公路建設(shè)器材和材料價格資料來源于一家信息資源公司（DRI）。見表一</p><p><b>　　模型結(jié)構(gòu)</b></p><p>　　本研究中一般公路造價預算模型由5個價格評價子系統(tǒng)組成。每個子模型評價一個建設(shè)優(yōu)勢地區(qū)支付項目代表的價格。建設(shè)優(yōu)勢區(qū)域是由不同地區(qū)的公路建設(shè)費用確定的。從路易斯安娜DOTD1984-1997年間的資料可

86、以發(fā)現(xiàn)超過50%的公路建設(shè)費用用于瀝青混凝土表面，波特蘭水泥混凝土表面，坑道和路基，鋼結(jié)構(gòu)，混凝土結(jié)構(gòu)和固型鋼。有趣的是，這些建設(shè)地區(qū)與那些用于評價FHWA CBPI的地區(qū)是一致的。鋼結(jié)構(gòu)建設(shè)是不包括在本模型中的，因為在其每個項目的超過98%的費用是以一個項目投標，并沒有用鋼數(shù)量的記錄，使其造價無法比較。模型中其他五項都由支付項目表示，其價格用比率表示更易比較。</p><p>　　每個子模型的建立是為了降低當年

87、描述各種建設(shè)投資的可變支付項目價格，考慮中的項目特征和那時良好的項目環(huán)境使項目很順利。在模型中嘗試盡可能多的獨立的各類因素使一般模型中影響建設(shè)造價的因素盡可能綜合和敏感。</p><p>　　包括五個子模型的整體模型如圖2所示。每個子模型從五個優(yōu)勢建設(shè)區(qū)域評價一個選擇性支付項目的價格。整體模型的每個子模型的貢獻是整合了與FHWA CBPI的索引表相似的索引表中的可選擇性支付項目的價格。在這里，因為這形式和FHWA

88、 CBPI有細小的差別而且是特別設(shè)計用來反映路易斯安娜過去和未來的整體建設(shè)造價的，所以它被命名為路易斯安娜公路建設(shè)索引并被解釋成：</p><p><b>　　有效性</b></p><p>　　模型執(zhí)行用資料被完美地生效而不是用于模型的評價。在這里沒有這樣的資料可利用。把現(xiàn)有的資料分成兩部分，一部分用于評價模型而另一部分用于驗證是不可行的，在一些子模型中有樣本規(guī)模限

89、制。舉個例子，混凝土鋪筑子模型一共只有212項觀測值，信息多樣但觀測值相對較少會降低對模型評價的精確度。所以模型執(zhí)行以觀察它怎樣重新觀測建設(shè)造價來評估。Fig3用模型測量出來的資料，1984-1997年間評價和觀察的LHCI值如Fig3所示。LHCI的95%信用限制在圖中顯示，舉個例子大多數(shù)情況下LHCI評價值包括了LHCI觀察值的95%的信用限制。LHCI評價和觀測值相似性測驗表明顯著的不同點在99%不能被注意到。</p>

90、<p>　　對圖3 中建設(shè)造價索引作用的研究解釋了觀測行為的原因。通過察看資料，觀察模型對預先計劃的影響，這使分析家找到了在過去一些時期中建設(shè)造價改變的主要原因。舉個例子，觀察1984-1986年間建設(shè)造價下降的主要原因要追溯到那段時期勞動力和石油價格的下降。1995年到1996年建設(shè)造價快速升高的根本原因是石油價格升高和小規(guī)模項目增多。緊隨其后建設(shè)造價的下跌（i.e., in 1997）主要原因是1996年承包的項目平均

91、規(guī)模的增大和項目平均持續(xù)時間的縮短。</p><p><b>　　結(jié)論</b></p><p>　　本研究已經(jīng)表明論文說明了公路建設(shè)造價的一個系列綜合原因。研究表明最有影響力的因素是用于建設(shè)設(shè)備的材料、人工和工具的費用。不管怎樣，個別項目的特點和項目的環(huán)境也影響工程造價。特別要指出，項目規(guī)模，持續(xù)時間，地點和項目投資對建設(shè)造價的影響也是非常顯著地。投資額，投資變動，計

92、劃改變的數(shù)量，在執(zhí)行中的變動、執(zhí)行標準的改變或者設(shè)計說明書的改動也能起到很大影響。其他會產(chǎn)生影響的因素不包括在本分析中因為缺乏相關(guān)可利用的數(shù)據(jù)。</p><p>　　本研究中的模型在整體水平下合理精確地重現(xiàn)了過去普通建設(shè)造價。建設(shè)預算在99%的重要性上與決算相差無幾。相較于個別項目，子模型只能獲得資料中42%—72%的變化程度的情況下，本研究采用整體水平的工程造價預測，從而提高了預測的正確性。令人懷疑的是這變化是

93、因為那些影響出價的非觀測的主觀因素。不管怎樣，個別項目中一些有特點的變化已經(jīng)在整體過程中被平均。</p><p>　　這模型判斷出到2015年如果過去的趨勢被推斷或通貨膨脹率作為評價未來建設(shè)造價依據(jù)，那么路易斯安娜的公路建設(shè)造價增長會比預期更快。根據(jù)模型預測，即使經(jīng)濟情況比預期更好、政府構(gòu)建未來項目使投資環(huán)境降低投資價格，公路建設(shè)造價增長會比預期更快的情況仍舊可能會流行，。建設(shè)造價中工程增加的主要原因是石油生產(chǎn)和

94、建設(shè)機器價格的預期增長。如果水泥鋪路用瀝青代替，或者建設(shè)機器上不可靠的設(shè)計包含在項目中，那么建設(shè)造價增長可能會較緩慢。</p><p>　　路易斯安娜的公路管理者可用者模型來測試不同的項目管理策略。擴大項目規(guī)模，縮短項目持續(xù)時間，減低出價量和種類，減少計劃改變數(shù)量，降低項目在最后四分之一階段解散的概率等都會降低整體建設(shè)造價。使用此模型，公路管理者能評估他們所信任的策略的影響。更重要的是，此模型能有助于評價未來建設(shè)