ANALYTICAL HIERARCHY PROCESS – INTUITIVE DECISION-MAKING TOOLS

OVERVIEW OF DECISION-MAKING

The ability to make informed decisions have been the most needed skill for every profession in the world. Most especially for professions that use a team system to achieve complex tasks. In the engineering profession, for example, joint collaborations in decision-making have yielded far greater results compare to individual decision-making. It is due to the concept of team decision making and approach that some of the greatest feats have been achieved in most technical fields. For example, a group of engineers designing a rocket from ground zero to be launched will have to make series of decisions on the budget, material type, design approach etc. Or a team of maintenance engineers at the national road authority or local road agency will have to decide which material should be used for the maintenance as well consider which defects have had a massive impact on the deterioration of the road pavement and must be treated first. Or yet still a coastal engineering team will have to decide which type and method of erosion defense mechanism should be used at the oceanfront to curb the constant erosion. The point is, making the right decisions in an organization is valuable, henceforth, using the necessary decision tools is an added advantage.

ANALYTICAL HIERARCHY PROCESS

To improve our decision-making processes there have been vast array of approaches and structural decision-making tools invented over the years. Interesting of them all I found, is the Analytical Hierarchy Process (AHP). It is a multi-criteria decision-making method originally developed by Prof. Thomas L. Saaty at the University of Pittsburg. It involves the derivation of ratios using the pairwise comparison (determining the weightiest of two or more significant ideas, methods, physical objects, preferences etc). The input parameters into this process can be physical measurements(unit cost in a selected currency, weight in Kg or lbs, length in km or feet) or subjective opinions(style, comfort, satisfaction, etc) which allows small inconsistency in judgment to represent its humanness. The output parameters are in ranking order. The highest of the rank is of the preference to be prioritized.

MAJOR STEPS INVOLVED IN THE AHP

There are five(5) major steps to arrived at the ranking of priorities as mentioned above. Step 1, like every normal decision-making process, must clearly define the OBJECTIVE. Step 2 allows for the objective decided in step 1 to be used to set the STANDARD. The standard includes the selection of criteria, sub-criteria, and alternatives. For example, if the selection of road construction material is the objective then selecting concrete or asphalt is the criteria, selecting the strength of both materials is the sub-criteria and the construction method as the alternative. Step 3, is to make a PAIRWISE COMPARISON of the standards created in step 2.(Example, compare the strength of concrete to asphalt, compare the comfort of asphalt riding surface to the concrete riding surface or the price of construction of both etc). Step 4 consist of a calculation of the WEIGHTING and the CONSISTENCY RATIO for the criteria, sub-criteria, and alternative selected in step 3. And finally, step 5 is the use of the weighting to evaluate the priorities according to the highest order of ranking.

A used of example is the easiest way to explain the process, henceforth, I have adopted an approach that is familiar to the engineering profession. But AHP can be used in a wide range of fields including psychology, AI systems, Social Sciences, Public Management etc.

A CASE SCENARIO FOR USE OF AHP BY THE MAINTENANCE TEAM IN BO DISTRICT, SIERRA LEONE

Hypothetically, let’s consider the Road Agency in Sierra Leone has decided to undertake a major maintenance program for several feeder roads in Bo District. The agency has not established a fully functioning asset management program, henceforth, it relies heavily on the maintenance engineering team to produce a viable report that clearly lay out evidence of roads to be prioritized in the maintenance programme.

Based on the indication that the maintenance team does not have a functional asset management platform (Highway Development and Management Series HDM-4, Pavement Management System, Bridge Management System etc) presents a scenario for the use of the analytical hierarchy process to deduced an accurate or near accurate report for management decision.

STEP ONE: ESTABLISH TASK OBJECTIVE

Therefore, the team adopts the AHP. The first step in the AHP as mentioned earlier is to define the objective of the task. The objective of this task is to provide management with a road maintenance prioritization scheme containing an index ranking(from the highest to the lowest) for all feeder roads in the Bo District, Sierra Leone.

STEP TWO: SET THE STANDARDS

The next step is to set the standard. Provide the criteria under which an evidence-based decision can be made concerning eligibility for individual roads within the scheme. To proceed with this step, the complete inventory and condition data of the roads in Bo District should be examined.

Below are typically the set of road data(inventory & condition) that have been collected from the feeder roads in Bo District.

Based on the examination of the road data above, there are several standards that can be used. Remembered, the analytical hierarchy process allows both objective standard (physical measurement) and subjective standard (opinion based). Different engineering teams can approach this step in many ways. One may decide to select the origin and destination of the road as a standard to judge its maintenance priority, others may decide the length of the road, and yet still another may decide on the defect types etc. For this example, the team has considered the defect types. The defects observed according to the assessment report in the tables above are divided into four types. The major deterioration(larger areas of the road has cracks and interconnected large potholes), minor deterioration (Road surface cracking, unconnected and mainly limited to the path of the tires) deflection (is the displacement in the formation of the road caused by loads, mainly traffic loads), and riding quality (the parameter for assessing the functional condition of the pavement as well as the roughness of the surface).

STEP THREE: USE PAIRWISE COMPARISON

Step 3 is the comparison of the standards agreed upon in step 2 above. Between the major deterioration and the minor deterioration which one is weighty – meaning it causes more damage to the road? Between the deflection and the riding quality which is higher in weighting to cause structural damage to the road. And the same for major deterioration to riding quality and minor deterioration to deflection etc. Compare the criteria against each other to find the criteria with a greater effect of damaging the road. Given the complexity in explaining the pairwise comparison, I have the matrix below to simplify the process. Considered Major deterioration = A, Minor Deterioration =B, Riding quality = C and Deflection = D

STEP FOUR: NORMALIZE COMPARISON BY ESTABLISHING THE WEIGHING

In Step 4 according to the procedure is intended to normalize the comparisons made in step 3 by dividing the rating of a defect in each cell by the total. This will produce the weighing matrix shown below.

Based on the weighting matrix above, the ranking of defects from highest to the lowest are major deterioration = 2.23, minor deterioration = 1.05, riding quality 0.23 and deflection 0.49. Individual ranking should be multiplied by the by individual defect value collected during the inventory and condition survey to derived the prioritization index.

The fundamental in the video below is a useful resource to better understand the pairwise comparison of items against each other.

STEP FIVE: PRODUCE PRIORITIZATION INDEX

After the process mentioned above, the table below highlights the sub-section of the roads in Bo District that should be prioritized by the management of the Highway Agency in Sierra Leone based on the highest ranking of the priority index shown in green.

CONCLUSION

I have found the AHP intuitive and interesting because of below reasons:

1. The broadness of AHP allows different users to interact with the process at different levels. It doesn’t confine its use to the top managers. It can be used by any group along the decision chain in any profession.
2. The flexibility of AHP broadens its use in a complex scenario as well as in simple decision but with multiple choices.
3. While it is a time-consuming theoretical process, its outputs are practical decisions that can be highly effective in application.
4. Its objective and subjective approach allow the use of in-depth knowledge and experiences or either one to deduce a useable decision.
5. It allows a decision to made in a relative short period of time.

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