Energy Savings from Increased Preventive Maintenance on Indiana Highways

Transcription

1 TRANSPORTATION RESEARCH RECORD Energy Savings from Inreased Preventive Maintenane on Indiana Highways EssAM A. SHARAF AND KuMARES C. SINHA In this paper are desribed the development of trade-off relationships between routine pavement maintenane ativities and the appliation of these relationships in estimating the savings in fuel used in pavement maintenane In Indiana. Two major routine pavement maintenane ativities were onsidered: pathing (orretive maintenane) and sealing (preventive maintenane). The results showed that when more sealing was done before winter less pathing was required after winter. Different highway lasses, pavement types, and geographi loations are taken into onsideration. The appliation example assesses possible ost savings in terms of savings in diret fuel onsumption by the maintenane equipment fleet. The trade-off onept is a entral issue in highway system analysis inluding pavement management systems (PMSs), maintenane management systems (MMSs), and other related areas (J). A trade-off relation is a way of determining how muh of one alternative has to be sarified in order to gain something of another alternative. In highway programming, trade-off relations an be used to split the available funds among different options at several levels. At the first level, trade-offs may be used to determine the split of total available funds between state roads and other loal roads. At the seond level, trade-off relations an determine portions of available funds to be alloated to speifi highway lasses (e.g., s and other state highways). At the third level, trade-offs may be used to distribute available funds between major maintenane ativities (federally funded ativities) and routine maintenane ativities (state-funded ativities). Finally, at the fourth level, trade-offs may be used to split available funds among speifi maintenane ations. Resurfaing, rehabilitation, and reonstrution are examples of major maintenane ations; and rak sealing, pothole pathing, and so on are examples of routine maintenane ativities. The last of the four levels is the most signifiant for a PMS as well as for an MMS beause this level deals with the alloation of funds to speifi maintenane ativities. The trade-off relations between two routine pavement maintenane ativities in Indiana, namely, pathing (orretive maintenane) and sealing (preventive maintenane), are disussed in this paper. Total routine pavement maintenane needs are first identified through a set of predition models; then trade-off relations are developed to indiate the split of total need between pathing and sealing ativities. Finally, an example is presented to show the use of the trade-off models in assessing possible ost savings in diret fuel onsumption. E. A. Sharaf, Department of Civil Engineering, Cairo University, Cairo, Egypt. K. C. Sinha, Shool of Civil Engineering, Purdue University, West Lafayette, Ind DATABASE The state highway system of Indiana is divided into two ategories: and other state highways (OSHs). In this study, the two highway systems were further subdivided by geographi loation (limati zones) and pavement type. Two geographi loations, north and south, were inluded to reflet the major limati differenes in Indiana. The pavement types onsidered were flexible pavement, rigid pavement, and resurfaed pavement. The units used for data olletion and analysis were 82 setions (a setion is defined as the portion of a highway within ounty limits). For eah of the 82 setions, four major groups of information were summarized: traffi, pavement harateristis, limati zone, and pavement maintenane reords. Traffi information inluded average annual daily traffi (AADT), perentage of truks, and equivalent axle load (EAL). Pavement harateristis inluded pavement type, layer thikness, and age. Climati zones inluded geographi areas with limates that are similar in terms of snowfall, rainfall, temperature differene, and so on. Finally, pavement maintenane reords inluded total prodution units, total man-hours, and types and quantities of materials. Pavement maintenane information was summarized for eah highway setion by ativity and by fisal year. The details of the development of this data base are given elsewhere (2, 3). An important feature of the study was that it used only those data that are routinely olleted by the Indiana Department of Highways (IDOH). DESCRIPTION OF MODEL In Indiana rigid pavement is the major type of pavement on the system (about 7 perent of total lanemiles), and flexible pavement and resurfaed pavement are the major pavement types on the OSH system (about 9 perent of total OSH lane-miles). The three ategories onstitute about 85 perent of the total lane-miles of state highway system in Indiana. Consequently, there are enough homogeneous setions of pavement type and harateristis to give 26 setions of rigid, 213 setions of OSH flexible, and 84 setions of OSH resurfaed. There were only a limited number of homogeneous setions in other pavement ategories (five setions for flexible, eight setions for resurfaed, and five setions for OSH rigid), and most of these setions were loated in the southern part of the state. These limitations were onsidered in the statistial analysis (4-6). The general form of the total routine pavement maintenane ost predition model is given in Equation 1. The model parameters are given in Table 1.

2 - 28 TRANSPORTATION RESEARCH RECORD 112 Log 1 (TC) = m * Log 1 (L, EAL) where + n * Log 1 (L, EAL) * (Z) TC = total pavement maintenane ost in dollars per lane-mile per year; L. EAL = aumulated equivalent axle load appliations during the entire age of the pavement setion (in thousands); and Z = dummy variable representing the loation of the setion (north or south). The term 'LEAL* Z was introdued to measure the effet of the interation between traffi level and limati zone. (1) lnterstal North 2 -.B -B 14 5 S lionsl 11 S tionsl u l. a BO B1 B2 BJ BO 81 B2 83 OSH North -.B 11 BB Sol1onsl - B L OSH 143 Selionsl TABLE 1 PARAMETERS FOR THE ROUTINE PAVEMENT MAINTENANCE COST ESTIMATION MODELS OF EQUATION 1 Pavement Category Par am et er Flexible Rigid Resurfaed OSH Flexible Rigid Resurfaed BO B3 BO B1 B2 All Setions 2 -,B 16 B 3 Sol1onsl -6 u -.4. a ,._ BJ m n R BO B1 B2 BJ FIGURE 1 Correlation analysis of sealing and pathing ativities based on perentage of ost alloated to eah. TRADE-OFF RELATIONS BETWEEN PATCHING AND SEALING ACTIVITIES Cost models were developed for individual maintenane ativity groups, namely pathing and sealing. The pathing group inluded shallow pathing and deep pathing. The sealing group inluded sealing longitudinal raks and joints and sealing raks. Pathing and sealing ativities aount for about 85 perent of the total pavement maintenane ost in Indiana (3), and there is a high orrelation between pathing and sealing performed in the same fisal year. The results of a detailed orrelation analysis performed on the portions of total ost alloated to pathing versus those alloated to sealing for different highway ategories and fisal years resulted in a orrelation value as high as -.65, as shown in Figure 1. The sheduling of different maintenane ativities in a fisal year (July-June) adds a partiular harateristi to the orrelation between pathing and sealing. This is beause sealing ativities usually preede pathing ativities in a fisal year. Sealing ativities take plae in the late summer and fall, and pathing usually takes plae in the spring. Although there may be some variation in the sheduling of these ativities, most sealing and pathing jobs are done during the periods mentioned. The high orrelation between pathing and sealing in a fisal year is a one-way orrelation that indiates that the amount of pathing done in a year is generally dependent on the extent of sealing performed before the winter. However, the sealing ativity does not depend on the pathing ativity. The general regression models for pathing and sealing follow the form presented in Equations 2 and 3. PS = a * Log 1 (L, EAL) + b * Log 1 (L, EAL) * Z (2) PP= * Log 1 (L, EAL) + d * Log 1 (L, EAL) * Z + e * PS (3) where PS is the perentage of total pavement maintenane ost alloated to the sealing group and PP is the perentage of total pavement maintenane ost alloated to the pathing group. The model parameters for the six pavement ategories are given in Table 2. The models indiate that, although an inreased traffi level requires an inreased level of pavement maintenane (pathing and sealing), the rate of inrease in the share of pathing ost as traffi level inreases is higher than that in the share of sealing ost. Furthermore, it an be onluded that pathing level (amount of pathing ativity taking plae after winter) is negatively affeted by the level of sealing (amount of sealing ativity taking plae before winter). That is, if more raks are sealed before winter, less pathing is required after winter, primarily beause of fewer potholes.

3 SHARAF AND SINHA 29 TABLE2 PARAMETERS FOR ESTIMATING PERCENTAGE OF TOTAL COST FOR PATCHING AND SEALING ACTIVITIES (Equations 2 and 3) Pavement Category Ativity Parameter Flexible Rigid Resurfaed Flexible Rigid Resurfaed Sealing a b R Pathing d O.Q e R OSH EXAMPLE OF USE OF TRADE-OFF MODELS One of the appliations of the trade-off models involves an assessment of ost savings in routine pavement maintenane in terms of diret fuel onswnption. ht the example given here, the energy ost savings assoiated with the trade-off between preventive maintenane (sealing) and orretive maintenane (pathing) are onsidered. Equation 3 established that the extent of pathing under a given traffi level is a funtion of the extent of sealing performed in the same fisal year. The impliation is that a higher level of prewinter preventive maintenane (sealing) an redue the extent of postwinter orretive or repair maintenane (pathing). It was also found that diret fuel onsumption (gallons per dollar spent) for sealing group ativities is less than for pathing group ativities (7, 8). Consequently, an inreased level of sealing ativity would not only redue the need for subsequent pathing ativities and thus improve overall pavement servieability, it would also ause savings in diret fuel onsumption for routine pavement maintenane. In this example five senarios were onsidered: inreasing sealing level by 5, 1, 15, 2, and 25 perent. For eah of these senarios total fuel onsumption (gallons per lane-mile per year) was alulated and then ompared with the urrent level of energy onsumption in order to estimate the amount of energy saved. With an inrease in sealing ativity, fuel onsumption for sealing would inrease. However, the inrease in sealing ativity would redue the level of pathing, and the orresponding derease in fuel onswnption would more than offset the inrease in fuel onsumption for the inreased level of sealing. The result would be a net savings in fuel onsumed by the maintenane equipment fleet. ht the following paragraphs a detailed explanation of the proedure for estimating energy savings at different traffi levels is presented. First, fuel onsumption rates in terms of gallons per dollar spent for both pathing and sealing groups were developed to avoid the differene in prodution units of the two groups. A summary of the resulting rates is given in Table 3. It an be seen that energy onsumption levels of the pathing group are onsistently higher than those of the sealing group. Energy savings were then alulated for all highway ategories under different traffi levels. For example, the ase of htterstate rigid pavement in the southern zone an be onsid- TABLE 3 ENERGY CONSUMPTION RATES FOR SEALING AND PATCHING GROUPS Energy Consumption Rates (gallons/dollar) North Highway Category Pathing Sealing Pathing Sealing, flexible.91.7 NA NA, rigid , resurfaed NA NA OSH, flexible OSH, rigid NA NA OSH, resurfaed Note: NA = not appliable. ered. Assuming a traffi level (awnulated EAL) of 2 million, the omputations are 1. From Equation 1 with appropriate parameters for rigid pavement, total pavement maintenane ost = $19.35 per lane-mile per year. 2. From Equation 2 with appropriate parameters for rigid pavement, perentage alloated to sealing = perent. 3. From Equation 3 with appropriate parameters for rigid pavement, perentage alloated to pathing = perent. 4. Sealing ost =.4215 * $19.35 = $8.23 per lane-mile per year. 5. Pathing ost=.4654 * $19.35 = $88.58 per lane-mile per year. 6. From Table 3, fuel onsumption rates are.94 gal per dollar of pathing and.65 gal per dollar of sealing. Energy onsumed in sealing= 8.23 *.65 = 5.22 gal per lane-mile per year. Energy onswned in pathing = *.94 = 8.33 gal per lane-mile per year. Total energy onsumption = gal per lane-mile per year. 7. For a 15 perent inrease in sealing ativity, the perentage of total pavement maintenane ost alloated to sealing is perent. 8. From Equation 3 with appropriate parameters for Inter-

4 3 TRANSPORTATION RESEARCH RECORD North 25% lnr1as1 in S1oling L1v1I 1. "' ;: :I:.8 l/l...j >. -;;;.6 g w g 4 2 % lnr1as1 in Sealing L1v1I 15 % lnreas1 in Sealing L1v1I 1 % Inrease in Sealing Level.2 5 % Inrease in Sealing L1v1I so Aumulated EAL 116) FIGURE 2 Energy savings due to inrease in sealing level for rigid pavement. state rigid pavement, the orresponding pathing perentage is 4.23 perent. 9. Repeating Steps 4 through 6 gives the new total energy onsumption as gal per lane-mile per year, whih results in a savings of.35 gal per lane-mile per year due to a 15 perent inrease in the urrent level of sealing. These omputations were repeated for all highway ategories for eah of the five levels of sealing ativity. The resulting savings in fuel onsumption for the three major highway ategories, rigid pavement, OSH flexible pavement, and OSH resurfaed pavement, are shown in Figures 2-4, respetively. The information summarized in Figures 2-4 was then used to estimate expeted total energy savings for the IDOH under the five options of inreasing sealing level. For example, for rigid pavement in the north, with an average traffi level of 25 million aumulated EAL, a savings of.15 gal per lane-mile per year an be expeted with a 5 perent inrease in sealing level. This is equivalent to about an.85 perent redution from the urrent level. Similar omputations were done for all other highway ategories under the average traffi level and 1. 1 I I.9 t North o.a l OJ "'.6 ;: :I: Vl >.. 5 1?'.Q w g " lnroaso in Sooting Levo! 2" lnroo.. in Sooting Lovol 15" lnroo.. in Sooting Lovol 1% lnr1as1 in Sealing L1v1I.2,1 a 1 a Aumulated EAL 11 Q6J FIGURE 3 Energy savings due to inrease in sealing level for OSH flexible pavement.

5 SHARAF AND SINHA 31 1,.. o ".. 9 B 7.?:.6 > "' " -:.. a >-..,5 w % Inrease in Seo ling Level 2 % Inrease 1n Sea ling Level 15 % Inrease 1n Sealing Level 1% Inrease in Sealing Level.2, 5 % Inrease in Sealing Lev I I Aumulalod EAL FIGURE4 Energy savings due to Inrease In sealing level for OSH resurfaed pavement. the orresponding perentage redutions in energy onsumption. These redution rates were then weighted by the perentage of total lane-miles of eah highway ategory. The resulting weighted value was taken as the average perentage redution in energy onsumption for the entire state highway system. Under a 5 perent inrease in sealing level, it was estimated that the average redution in energy onsumption would be about.82 perent. The orresponding redution rates were 1.64, 2.5, 3.3, and 4.1 perent with an inrease in sealing level of 1, 15, 2, and 25 perent, respetively. With an estimated. 7 million gallons of fuel diretly onsumed by the equipment fleet in pavement maintenane ativities (8), the expeted savings in motor fuel onsumption an be 5,7, 11,5, 17,2, 23, and 28,7 gal, respetively, under the five levels of inrease in sealing ativity. It should be mentioned here that the energy savings are only the diret benefits of inreasing the sealing level. There are also several indiret benefits assoiated with an inreased sealing program. With an inreased level of sealing, the amount of pathing required is redued, whih indiates a lower level of pavement damage (e.g., potholes). A lower level of pavement damage would improve traffi safety and provide a higher level of servie to highway users at less vehile operating ost. CONCLUSIONS On the basis of the findings of this study, the following major onlusions an be drawn: 1. There is a definite trade-off relation between the amount of sealing (preventive routine maintenane) and that of pathing (orretive maintenane). This trade-off relation is negative, whih indiates that if more sealing is done before winter, less pavement repair (pathing) is required after winter. 2. A diret ost savings, attributable to redution in fuel onsumption by the routine maintenane equipment fleet, ould be ahieved by inreasing the level of sealing ativity. 3. The developed trade-off relations indiated that the level of servie and effetiveness of routine maintenane dollars ould be inreased through inreasing the sealing level, whih in tum results in a redution in required pavement repair (less pathing). REFERENCES 1. M. J. Markow. Conepts, Methods and Appliations Relating to Pavement Maintenane and Rehabilitation. Moderator Report for Session 7. North Amerian Pavement Management Conferene, Toronto, Ontario, Canada, K. C. Sinha, T. F. Fwa, E. A. Sharaf, A. B. Tee, and H. L. Mihael. Indiana Highway Cost Alloation Study. Report FHWA/IN/JHRP- 84/2. Purdue University, West Lafayette, Ind., E. A. Sharaf and K. C. Sinha. Analysis of Pavement Routine Maintenane Ativities in Indiana. In Transportation Researh Reord 985, TRB, National Researh Counil, Washington, D.C., 1984, pp E. A. Sharaf and K. C. Sinha. Estimation of Pavement Routine Maintenane Costs. In Transportation Researh Reord 951, TRB, National Researh Counil, Washington, D.C., 1984, pp K. C. Sinha, E. A. Sharaf, J. D. N. Riverson, and S. M. O'Brien. The Role of Maintenane Cost Analysis and Predition in Pavement Management. Pro., North Amerian Pavement Management Conferene, Toronto, Ontario, Canada, E. A. Sharaf and K. C. Sinha. Energy Conservation and Cost Saving Related to Highway Routine Maintenane: Pavement Maintenane Cost Analysis. Report FHWA/IN/JHRP-84/15. Purdue University, West Lafayette, Ind., E. A. Sharaf, K. C. Sinha, E. J. Yoder, and C. Whitmire. Field Investigation of Resoure Requirements for State Highway Routine Maintenane. In Transportation Researh Reord 943, TRB, National Researh Counil, Washington, D.C., 1983, pp E. A. Sharaf, K. C. Sinha, and E. J. Yoder. Energy Conservation and Cost Saving Related to Highway RouJine Maintenane: Data Colletion and Analysis of Fuel Consumption. Report FHWA/IN/ JHRP-82/23. Purdue University, West Lafayette, Ind., Publiation of this paper sponsored by Commillee on Pavement Mainle nane.