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in existing practices. Sustainable practices include increased Table 1. Grouping structure of the alternative-
use of recycled materials, industrial by-products, and local preference screening matrix.
materials; decreased use of energy-intensive materials and
General Version Example
construction processes; improvements in material produc- Group A Economic factors
tion and processes; techniques that preserve or increase the Factor A1 Initial costs
Factor A2 Future rehabilitation costs
longevity of pavements; and eco-friendly design alternatives. ... ...
Life-cycle assessment (LCA) methods typically are used in Factor An User costs
Group B Construction factors
evaluating the environmental impact of materials, equip- Factor B1 Continuity of adjacent lanes
ment, and processes used in pavements. The LCA-based Factor B2 Traffic during construction
environmental impacts can be incorporated qualitatively or ... ...
Factor Bn Lane geometrics
quantitatively in the pavement-type selection process. Group C Local factors
Factor C1 Availability of local materials
Factor C2 District/local preferences
5.4 Weighing of Economic and ... ...
Factor Cn Stimulation of competition
Noneconomic Factors Using Group D Other factors
Alternative-Preference Factor D1 Noise
Factor D2 Subgrade soils
Screening Matrix ... ...
Factor Dn Experimental features
The pavement-type selection process should weigh both
economic and noneconomic factors to ensure that the agency
goals and policies are incorporated in decision making. An Table 2. Group weights of the screening matrix.
alternative-preference screening matrix is suggested for this General Version Example
purpose. The screening matrix is a decision support tool that is Group Weight Group Weight
A WA% Economic factors 50%
designed to help agencies determine whether there are advan- B W B% Construction factors 25%
C W C% Local factors 10%
tages in selecting one alternative over others and whether these D WD% Other factors 15%
alternatives should be evaluated more closely. Total score = Total score =
100% 100%
The following sections describe how to set up the screening Note: W = weight.
matrix and evaluate the results obtained. Appendix A illus-
trates the application of the screening matrix and includes an
example of its use. tors and groups may vary from project to project
within an agency.
Step 1: Identify and Group Evaluation Factors Step 2: Assign Group and Individual Factor Weights
The economic and noneconomic factors that have a Next, weights must be assigned to each of the factor
potential impact on the pavement-type selection groups and each factor within a group to reflect their
process for a given project are identified and grouped. importance to the pavement-type selection process for
The factors identified in Sections 5.2 and 5.3 are sug- a given project. Table 2 and Table 3 illustrate the group
gested. A suggested grouping structure and sample and factor weighing scheme, respectively. The factor
factors are illustrated in Table 1. The factor groups groups and factors within a group can be assigned
could include economic factors, construction fac- equal or unequal weights, but the sum of all group
tors, local factors, maintenance factors, traffic and weights and all the factor weights within each group
safety factors, environmental factors, and others. must equal 100 percent.
Agencies are expected to modify the contents of Step 3: Assign Preference Rating of Individual Factors
Table 1 as necessary to best suit their goals, expecta- To facilitate a comparative evaluation of alternatives,
tions, and project requirements. The evaluation fac- the evaluation factors are assigned with preference
Table 3. Factor weights of the screening matrix.
General Version Example
Group A Weight Economic Factors Weight
A1 WA1% Initial costs 30%
A2 WA2% Future rehabilitation costs 25%
A3 WA3% Road-user costs 20%
An WAn% Future maintenance costs 25%
Group total = Group total =
100% 100%
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Table 4. Sample rating guidelines for the alternative-preference
screening matrix.
Factor Low Medium High
Initial costs Cost >10% Cost >5% and <10% Cost within 5%
Life-cycle costs Cost >20% Cost >10% and <20% Cost within 10%
User costs User cost >20% User cost >10% and <20% User cost within 10%
Future rehabilitation costs Cost >10% Cost >5% and <10% Cost within 5%
Future maintenance costs Cost >10% Cost >5% and <10% Cost within 5%
Significant complexity Moderate complexity to
Roadway/lane geometrics Easy to accommodate
to accommodate accommodate
Continuity of adjacent Some significant issues
Significant issues No significant issues
pavements possible
Continuity of adjacent Some significant issues
Significant issues No significant issues
lanes possible
Availability of local Lack of local
Some experience Commonly used
materials and experience experience
Very difficult to Somewhat difficult to
Traffic during construction Easy to accommodate
accommodate accommodate
Much higher noise Some increased noise No difference in noise
Noise
likely possible generated
Significant issues for Some issues possible for No significant issues
Subgrade soils
construction construction for construction
District/local preference No preference Some preference Significant preference
Significant issues
Some issues related to
Safety considerations related to safety Better safety features
safety features
features
Conservation of Much higher materials/ Somewhat higher No significant
materials/energy energy use materials/energy use difference
Very few capable Common experience
Stimulation of competition Some experience
contractors for each
Little to no local Common experience
Maintenance capability Some experience
experience for each
Very difficult to Somewhat difficult to
Future needs Easy to accommodate
accommodate accommodate
National but no local New and unproven
Experimental features Common technology
experience technology
ratings using predetermined criteria. The purpose of Initial Cost factor is assigned a preference rating of
the ratings is to quantify the relative advantages and "high" when the initial cost value of an alternative
disadvantages among the alternatives for each evalu- is within a 5 percent difference of the lowest values
ation factor. When an alternative offers significant of all candidates or "low" if the initial cost difference
advantages associated with a given evaluation factor, of the alternative exceeds 10 percent of the lowest
then the alternative is rated with a high preference for value.
that factor. Step 4: Score Pavement-Type Alternatives
The rating scheme can be discrete or continuous. Upon assigning preference ratings, the numerical
While a discrete rating scheme is simple to use, a con- weighted scores of evaluation factors and groups are
tinuous rating scheme provides more flexibility for calculated for each alternative. Ratings of "low,"
users. As with factors, groups, and weights, it is pro- "medium," and "high," if used, should be converted
posed that the agencies develop their own rating guide- to numerical scores. Table 5 presents example crite-
lines that reflect their goals and expectations. As a first ria for converting these ratings to a numerical scale.
step, each agency should ask decision makers about the
factors they currently use in making pavement-type
decisions and what additional factors should be con- Table 5. Example criteria for
sidered in the process. Test runs should be made on preference rating.
several older projects to determine if the proposed
Preference Rating Numerical Score
screening process results in acceptable pavement selec- No difference 0%
tions. The pavement-type selection committee can Low 20%
Medium low 40%
help establish these guidelines for the agency's use.
Medium 60%
Table 4 provides sample guidelines on rating indi- Medium high 80%
vidual factors on a discrete scale. For example, the High 100%
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Table 6. Example of the calculation of weighing
scores for individual factors.
Individual
Preference Numerical Weighted
Economic Factors Factor
Rating Rating Score
Weight
Initial costs 30% Medium 60% 18.0%
Future rehab costs 25% High 100% 25.0%
User costs 20% Low 20% 4.0%
Future maintenance 25% Medium- 40% 10.0%
costs low
Total unweighted score for Economic Factors 57%
For a given alternative, the numerical scores of each Agencies should determine their own criteria to
evaluation factor are multiplied by their correspon- interpret the screening-matrix results. An agency can
ding factor weights to calculate the weighted scores of develop a threshold value to determine how different
factors. The sum of weighted scores of factors within the alternatives are. For instance, if the difference in
each group is the unweighted score of that group. The the final scores of two alternatives is more than 10, the
example in Table 6 calculates the weighted score for alternative with the higher score can be selected as the
individual factors within the Economic Factors group preferred one.
and the unweighted score for that group. The weighted Recognizing that the project goals and the choice of
group scores are then calculated by multiplying their feasible alternatives are unique to each project, this
unweighted score by their corresponding group weights guide recommends the application of informed judg-
(see Table 7). The sum of weighted group scores is the ment and agency experience in the selection process,
total score for that alternative; it should not exceed with or without a threshold criterion in place. The
100 percent. screening matrix provides a systematic framework
Step 5: Interpret Results for practical decision making by setting "musts" and
Based on the final scores of alternatives, the "best pos- "wants" of an ideal choice for the project, exploring
sible" pavement-type alternatives are selected. and prioritizing alternatives based on their strengths
When the final score of an alternative is higher than and weaknesses, and choosing the most-preferred
that of other candidates, the alternative with the high- alternative(s).
est score may be much better suited than others. How- Table 8 provides a template of the screening
ever, when the final scores of multiple alternatives are matrix. Users can add or eliminate any number of
comparable, any of these alternatives could be selected. alternatives, groups, and individual factors within a
Such cases are well suited for alternate bidding. If no group, as appropriate. Appendix A illustrates the
alternative appears to be satisfactory, further investi- application of the alternative-preference screening
gation is needed. matrix.
Table 7. Example of the calculation of weighted
group scores.
Group Unweighted Group Weighted Group
Group
Weight Score Score
Economic factors 50% 57% 28.5%
Construction factors 25% 45% 11.3%
Local factors 10% 25% 2.5%
Other factors 15% 15% 2.3%
Total score of the matrix 44.6%
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Table 8. Alternative-preference screening-matrix worksheet.
Factor Alternative 1 (Alt1) Alternative 2 (Alt2)
Factor
Weight Rating Weighted Score Rating Weighted Score
Group A
Factor A1 WA1 RA1-Alt1 WA1*RA1-Alt1 RA1-Alt2 WA1 * RA1-Alt2
Factor A2 WA2 RA2-Alt1 WA2 *RA2-Alt1 RA2-Alt2 WA2 *RA2-Alt2
Factor A3 WA3 RA3-Alt1 WA3 *RA3-Alt1 RA3-Alt2 WA3 *RA3-Alt2
Factor An WAN RAN-Alt1 WAN *RAN-Alt1 RAN-Alt2 WAn *RAN-Alt2
Group A unweighted total 100% (WAi*RAi-Alt1) (WAi * RAi-Alt2)
Group B
Factor B1 WB1 RB1-Alt1 WB1*RB1-Alt1 RB1-Alt2 WB1*RB1-Alt2
Factor B2 WB2 RB2-Alt1 WB2 *RB2-Alt1 RB2-Alt2 WB2 *RB2-Alt2
Factor B3 WB3 RB3-Alt1 WB3 *RB3-Alt1 RB3-Alt2 WB3 *RB3-Alt2
Factor Bn WBN RBN-Alt1 WBN *RBN-Alt1 RBN-Alt2 WBn *RBN-Alt2
Group B unweighted total 100% (WBi*RBi-Alt1) (WBi*RBi-Alt2)
Group C
Factor C1 WC1 RC1-Alt1 WC1*RC1-Alt1 RC1-Alt2 WC1*RC1-Alt2
Factor C2 WC2 RC2-Alt1 WC2 *RC2-Alt1 RC2-Alt2 WC2 *RC2-Alt2
Factor C3 WC3 RC3-Alt1 WC3 *RC3-Alt1 RC3-Alt2 WC3 *RC3-Alt2
Factor Cn WCN RCN-Alt1 WCN *RCN-Alt1 RCN-Alt2 WCn*RCN-Alt2
Group C unweighted total 100% (WCi*RCi-Alt1) (WCi*RCi-Alt2)
Group D
Factor D1 WD1 RD1-Alt1 WD1*RD1-Alt1 RD1-Alt2 WD1*RD1-Alt2
Factor D2 WD2 RD2-Alt1 WD2 *RD2-Alt1 RD2-Alt2 WD2 *RD2-Alt2
Factor D3 WD3 RD3-Alt1 WD3 *RD3-Alt1 RD3-Alt2 WD3 *RD3-Alt2
Factor Dn WDN RDN-Alt1 WDN *RDN-Alt1 RDN-Alt2 WDn*RDN-Alt2
Group D unweighted total 100% (WDi*RDi-Alt1) (WDi*RDi-Alt2)
Subtotals Group Group Group Weighted Group Group Weighted
Weights Unweighted Total Unweighted Total
Total Total
Group A WA (WAi*RAi-Alt1) WA *(WAi*RAi-Alt1) (WAi*RAi-Alt2) WA *(WAi*RAi-Alt2)
Group B WB (WBi*RBi-Alt1) WB *(WBi*RBi-Alt1) (WBi*RBi-Alt2) WB *(WBi*RBi-Alt2)
Group C WC (WCi*RCi-Alt1) WC *(WCi*RCi-Alt1) (WCi*RCi-Alt2) WC *(WCi*RCi-Alt2)
Group D WD (WDi*RDi-Alt1) WD *(WDi*RDi-Alt1) (WDi*RDi-Alt2) WD *(WDi*RDi-Alt2)
Grand total 100% Final score- Alt 1 Final score- Alt 2
