1 Introduction

The primary role of the post office is collecting, scanning, sorting, transmission; and delivery of mail with consistent, speed, and security. The Indian postal service has taken a significant role in sorting and transporting the mails throughout the countries. Though the degree of the sorting process varies from country to country, the ultimate aim is to make letter-sorting a fully customized one. For example, developed countries such as the USA, Japan are using the automatic sorting machine to increase their delivery speed, whereas, in India, sorting is being done manually because of abundant labour availability. The processing, transmission, and delivery of mail are the core activities of the postal department. In India, daily mails are collected from almost 579,595 letterboxes and processed through a network of 389 mail offices by roads, rails, and airlines transportation.

The NSH sorting process is based on two types of mails/articles such as Town Delivery (TD—local mails) and Non-TD articles (except local mails). Recently, NSH has worked on the Mail Network Optimization Project (MNOP) to improve the standardization and operational processes in terms of mail processing, transmission, and delivery (McKensy India Post mail Network Optimization Project 2010). In this context, a vital part of the work was involved in modifying the existing layout design to enhance operational excellence by increasing the production of delivery articles to reach the customer on time.

Creating a FLD is a multi-objective problem task and it involves many inputs, either quantitative or qualitative in nature. FLD problem contains algorithms, or it will generate the alternate layouts within the layout space. According to Yang and Kuo (2003), neither an algorithmic nor a procedural layout design methodology is usually useful in solving a practical design problem. Therefore, an AHP method can be implemented to find the optimum layout to improve operational performance through lean service evaluation.

In industries AHP has been well-accepted for multi-criteria decision-making. The application of AHP is to make a decision based on criteria, sub-criteria and alternatives forms the complete hierarchy process. The benefit of AHP is its capability to accommodate subjectivity and inconsistency in human judgments. It can deal with ill-structured and multi-criteria problems without severe complexities (Saaty 1990).

1.1 Rationale of the study

This study is helpful for the researchers who are trying to evaluate the optimal layout selection among the alternatives to enhance operational performance. This study also expected the interest of HR managers and a large number of employees who play an essential role in judging the layout alternatives for production efficiency. Postal administration is planning towards growth in operational performance and working environment to enhance the production as well as protect the employees from cramping working conditions. Hence, we have considered 2 main criteria and its relevant sub-criteria to judge the feasible layout. Most of the layout evaluation so far was done in manufacturing industries but not much in service industries, particularly postal service sector. Further, it is evident that the researchers have not conducted any study on postal service layout evaluation in recent years.

The present study will focus on understanding the ideal system for evaluation of the layout design to enhance operational performance.

The key research questions which will be addressed in the study are:

  1. 1.

    How is the performance evaluation of India Post facility layout been judged for the enhancement of operational performance?

  2. 2.

    What is the role of managers and employees in ensuring the operational performance layout among the different alternatives?

1.2 Objectives of the study

The main objectives are:

  1. 1.

    To study the role of performance evaluation of India Post facility layout for the improvement of operational performance;

  2. 2.

    To understand the role of the managers and employees in ensuring the operational performance layout among the different alternative.

This paper organized in the following sequence: Literature reviews about FLD and addressing the research gap followed by research methodology. Then a discussion of the case study of NSH, Mangalore, Karnataka, and South India is taken up. The paper summarizes the result analysis and managerial implications concluding with directions for further research.

2 Literature review

2.1 Quantitative techniques applied in FLD problems

There are many algorithms/computer programs and heuristic methods involved to address this type of FLD problems. Among them, the famous algorithms/computer programs such as CRAFT (Computerized Relative Allocation of Facilities Technique; Buffa 1964), CORELAP (Computerized Relationship Layout Planning; Lee 1967) and ALDEP (Automated Layout Design Program; Seehof and Evans 1967). These algorithms worked on the decision makers’ preference to answer the question of which machine or department/section has to allocate with the next location in the systematic layout procedure. Unfortunately, these algorithms are not assured for the complete qualitative data for the optimal layout design, whereas it leads to suboptimal solutions.

The layout design problem is the leading research field in manufacturing and service industries to perform the efficiency and profitability (Meller and Gau 1996). Hu and Wang (2004) and Zouein et al. (2002) established a rule-based design approach using a genetic algorithm (GA) to resolve the unequal area layout problem. In this paper, the multiple objective functions such as MFFC (Material Flow Factor Cost), SRF (Shape Ratio Factor) and AUF (Area Utilization Factor) to reach minimum TLC (Total Layout Cost). Paul et al. (2006), explained the facility layout problem solved by PSO (Particle Swarm Optimization) algorithm, and proposed the method of finding the distance between the facilities. In addition, GA and improved GA comparison of the algorithm was analyzed to find out the efficiency of the algorithms. The Paes et al. (2017) addressed the unequal-area FLP for minimizing the distances among facilities assigned by material-handling flows. They introduced a basic GA, and an improved GA through partial solution deconstructions and reconstructions. Guan and Lin (2016) used a hybrid algorithm based on variable neighbourhood search, and ant colony optimization to solve the single row facility layout problem. Whereas, Tayal and Singh (2017) integrated heuristic (Simulated Annealing) and MCDM method (TOPSIS) to find the optimal layout selection. Vadivel et al. (2018) applied GA to find minimum layout cost and DEA for finding efficiency layout among the alternatives in India Post facility layout design. Benmouss et al. (2019) used AHP for ergonomic evaluation in information systems. It consists of 16 criteria grouped in 4 categories such as accessibility, usability, persuasivity, and emotionality. Meena et al. (2019) applied AHP and Fuzzy AHP methods in Indian agri-food supply chain (AGSC). Besides, these methods were used to priorities their strengths, weaknesses, opportunities, and threats factors of AGSC. Singh and Prasher (2019) integrates Fuzzy AHP and SERVQUAL methods to measure the service quality in 4 Punjab hospitals, India. Fuzzy AHP used to find the best hospital among four hospitals from the patients’ point of view.The above authors used algorithms and heuristics to generate optimal layout using quantitative data.

2.2 MCDM tools applied in FLD problems

Initially, Cambron and Evans (1991) applied the AHP technique on printing plant in a standard and hierarchical form to find the optimum layout design. Following that, Yang and Lee (1997) recommended the AHP decision model for the selection of facility layout in IC packaging industries. Foulds and Partovi (1998) developed combined AHP with a graph-theory based DSS for generating a scaled block plan for the construction of the municipal building. Hence, it is evident that AHP is one of MCDM technique to solve FLD Problems. In this context, refer Table 1 for the detailed literature support for FLD with MCDM techniques.

Table 1 Brief literature review on MCDM tool applied to FLD problem
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Based on the above literature, there has been a limited number of papers applied AHP in FLD problem for the service industries in the specific, postal service industry. Also, this method allows incorporating tangible and intangible factors that would fulfill the objectives of optimal layout selection. We have considered two criteria’s such as cost division and work environment division with 14 sub criteria’s for the selection of postal layout operational performance. Literature support has been included for choosing criteria and sub-criteria, as presented in Table 2.

Table 2 Brief information of each criterion and sub-criterion with reference
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3 Research methodology

Many journal papers reviewed for choosing critical criteria and sub-criteria. The methodological framework of AHP techniques, as shown in Fig. 1.

Fig. 1
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Flowcharts for the proposed AHP methodology facilities layout

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3.1 Decomposition of structural hierarchy

Decomposition breakdowns a problem into controllable elements individually. It begins with inherent descriptions of the problem (Selection of optimal layout) and proceeds logically to the criteria such as cost and work environment.

After the goal decomposed into manageable element, it should be structured into a hierarchy. Certain things must be prioritized while building the hierarchy as below:

  • Goal (selection of best layout) kept on top of the hierarchy.

  • Decompose the goal into sub-goals (cost and work environmental branch).

  • Further, decompose sub goals into necessary sub-criteria (attributes) to measure the goals.

  • Alternatives added to the bottom of the hierarchy (layouts 1–7).

3.2 Preference measurement and priority synthesis

A comparative scale used for the pair-wise comparisons of the attributes in each level of hierarchy formation. Pair-wise comparisons made using verbal statements about the strength of dominance (importance or likelihood) of one attribute to other attribute symbolized using Saaty rating scale [1–9]. Then, the matrix structure has been formed to develop a local priority vector. After that, we have to combine the local priorities to obtain a global weight for the final decision. The priority vectors can be computed using—Eigenvalue/Eigenvector method, simple average method, weighted average method (refer “Appendix”). Then global weight can be calculated by adding from the top level to the bottom level of the hierarchy. (Saaty 1990).

3.3 Consistency ratio

The comparisons obtained on subjective assessment; a consistency ratio is needed to check the accuracy. A comparison matrix “A” is said to be consistent if aij * ajk = aik for all i, j, and k. However, consistency shall is required. Too much flexibility is disagreeable because of this method contracts with human judgment. Saaty (1990) demonstrated that for consistent reciprocal matrix, the largest Eigenvalue is equal to the size of the comparison matrix, or \( {\mathbf{\gimel max}} = {\mathbf{n}} \). Then Saaty described the measure of consistency, called Consistency Index (CI) as deviation or degree of consistency using Eq. 1.

$$ {\mathbf{CI}} = \frac{{({\mathbf{\gimel max}} - {\mathbf{n}})}}{{({\mathbf{n}} - 1)}} $$
(1)

Further, CI recommended for comparing it with the appropriate one. The appropriate Consistency index is called Random Consistency Index (RI). Saaty randomly generated reciprocal matrix using scale 1/9, 1/8,…, 1,…, 8, 9 and get the random consistency index to see if it is about 10% or less.

The random consistency index can be calculated using Eq. 2.

$$ {\mathbf{RI}} = 1.98*\frac{{({\mathbf{n}} - {\mathbf{2}})}}{{\mathbf{n}}} $$
(2)

Then, he suggested Consistency Ratio, which is a comparison between the Consistency Index and Random Consistency Index using Eq. 3.

$$ {\mathbf{CR}} = \frac{{{\mathbf{CI}}}}{{{\mathbf{RI}}}} $$
(3)

If the value of Consistency Ratio is lesser or equal to 10%, the inconsistency is adequate. If the Consistency Ratio is greater than 10%, the subjective judgment is needed to be revised or eliminate the questionnaire form of the decision makers.

4 The model applied in NSH Mangalore—a case study

The facility layout consists of 5 active areas, as shown in Table 3. Important mail flow exists among 1 of the 5 active areas shown in the table, known as relationship chart (REL). These ratings (a for absolutely necessary, e for especially important, i for important, o for ordinary closeness OK, and x for unimportant) are used to denote the significance related with two departments located next to each other. This facility layout was generated with the help of REL chart and space necessities of the departments, as shown in Table 4.

Table 3 Active areas of department
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Table 4 Mail flow REL charts
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The existing layout has many problems as follows: (refer Figs. 2 and 3)

  • Cycle time is long (171 s/article)—verified in value stream map.

  • The employee feels not comfortable for long time work—confirmed in a questionnaire survey.

  • There is no emergency exit for the whole layout.

  • There is a chance of mixing of received and dispatch bags (backtracking mails).

  • Present production delivery articles (12,000 articles/day) are not satisfactory as compared to the target.

Fig. 2
figure 2

Value stream map—existing layout

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Fig. 3
figure 3

National speed post hub (NSH) Mangalore—current layout

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4.1 Facility layout design

Seven alternative layouts have considered because each layout has its own merits and demerits. For example, layout 1 suitable for space utilization. Layout 2 is good for an arrangement of light facilities. Layout 3 is appropriate for minimum throughput time. Layout 4 is fit for ease of supervision and security concerns. Layout 5 is apt for process suitability and handling the equipment accessories. Layout 6 is flexible for mail flow and personal flow. Finally, layout 7 is suitable for aesthetics and comfort to the postal employees. These seven layouts meet all the expectations from postal managers to employees by careful observation through interview and questionnaire study—initially, 18 layouts drawn in different combinations of layout design. The brainstorming sessions conducted among the postal employees. Then, it reduced to 7 layouts which had been accepted by both managers as well as workers for the evaluation of feasible layout. After that, these 7 layouts drawn by Computer Aided Software (CAD) tools (refer Fig. 4).

Fig. 4
figure 4

Alternatives layout design from CAD

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Initially, we started with the following important observations such as light facilities, pollution control, throughput time, housekeeping, safety, backtracking, and bypassing process.

4.2 Formation of hierarchy

Criteria by which the layouts can judge are numerous. So, the two main criteria cost and work environment division are applied to decide the optimal layout from the seven alternatives, and it is relevant to sub-criteria. For example, the movement of mail flow is the most common and valuable criteria used to judge layouts under cost divisions sub-criteria. Previously, developed REL charts clearly shows the most critical route (i.e.) scanning—Sorting and Dispatch. This paper recommends seven layout design alternatives to evaluate the feasible layout selection such as Layout 1, Layout 2, Layout 3, Layout 4, Layout 5, Layout 6 and Layout 7 as shown in Fig. 4 (Fig. 5).

Fig. 5
figure 5

Hierarchy formations for the selection of facility layout

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5 Result analysis

5.1 Numerical calculation

Pairwise comparisons were made and then converted into the framework of a matrix used to develop a local priority vector as an estimate of relative magnitudes related to the elements compared.

The overall priority of the alternative computed as follows (refer Table 5):

Table 5 Overall values of facility layouts projected by postal layout using AHP
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$$ {\text{Global}}\,{\text{rating}} = \sum ({\text{Priority}}\,{\text{of}}\,{\text{alternative}}\,{\text{concerning}}\,{\text{subcriteria }}) \times ({\text{Relative}}\,{\text{priority}}\,{\text{of}}\,{\text{sub}}\,{\text{criteria}}) $$
(4)

Inference on AHP:

$$ {\text{A}}_{6} > {\text{A}}_{4} > {\text{A}}_{5} > {\text{A}}_{1} > {\text{A}}_{2} > {\text{A}}_{7} > {\text{A}}_{3} . $$

From the above Table 6 and seven based on the comparison, optimal layout 6 has been selected, since it has the highest weight (0.22587) among seven alternative layouts. Based on the preference, in AHP, layout 4 is at the second choice. In Table 5 exemplified the global layout ratings using the AHP method. Practically, sensitivity analysis could be made to determine the robustness in the pairwise rankings. Finally, the postal department agreed and adopted layout 6 as its operational performance-oriented layout.

Table 6 Overall rating of the facility layouts alternatives
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5.2 Practical managerial implications

FLD problem can be solved either by the company looking for a new site or trying for a new business in the existing departments or interchanging departments. This paper presents the AHP model for India Post seeking operational excellence through modifying the inter-changing departments and simplifying the process through a single piece flow. The hierarchical structure illustrated in Fig. 4 is a simplified and well-structured one. Hence, the AHP model can help the decision makers to examine the numerous layout designs, assessing layout alternatives, and choose the optimal one.

The hierarchy structure starts with the goals of the organisation followed by criteria, sub-criteria, and ending with alternatives (complete hierarchy chain). The AHP model provides the decision makers’ the various priorities focusing towards layout characteristics, employees’ managerial experience, and their judgment. This research work was oriented towards India Post service to improve the operational excellence through production and betterment of the working environment. The main goal of the AHP decision model is to satisfy the decision makers to choose from alternative designs of facility layout problems. In reality, FLD is a complex problem in order to select optimal one from a set of layout design alternatives.

The data provided in these FLD problems are explored with suitable data sets from India Post service by identifying the issues and modifying the entire existing layout. The modifying layout has some advantages, as follows:

  • Improved production rate 9.62% from 8620 delivery articles.

  • Improved housekeeping.

  • Improved working environment.

  • Improved mail flow with an organization (inbound flow).

Initially, postal employees did their sorting in a line sequence. The movement of the personnel during the sorting process takes longer cycle time (171 s/article) between town delivery articles and non-town delivery articles. After modifying the facility layout TD and Non-TD was separated and cellular approach was implemented (grouping the sorting case into TD and Non TD sorting case). After that, the cycle time (157.32 s/article) and walking distance of employees’ movement reduced. Initially, separate sections of trolley, basket, and empty bags were not provided. After modifying the facility layout, we have provided these sections and improve the housekeeping through 5S and visual management. All these modifications’, were supported by the postal department, they also spent approximately INR 2.0 Lakhs for the implementation.

The AHP layout model helps the managers to analyse the hierarchical structure entirely well in advance. Managers can gather the required information, time allocation, cost expansion, and also get the support from the employees by choosing the most optimal layout design. The managers can also understand the area of improvement by visualizing the complete hierarchy structure during a brainstorming session among the postal employees. The layout changes or finding the new location is subject to the location site or layout characteristics and the management requirements.

A general complaint from practitioners is that righteous judgment or comparison between layouts on qualitative factors are purely based on subjective consistency. Providing the right result is beyond the nature of human beings. In a practical sense, the proposed AHP layout model was attractive to the managers in the way of pair-wise comparison mechanism. Hence, managers are giving the relative grading rather than absolute preference, at a time, on qualitative items. It is observed that the projected AHP layout model is exciting and practically provides insight into industrial engineers and managers. The AHP layout model, which has been implemented successfully in NSH can be a benchmark for the other postal service, focusing on the enhancement of operational performance.

6 Conclusion

This paper presents the AHP methodology to select the best and optimum layout (Layout 6) among the seven alternatives discussed. The advantage of this research is to choose the best layout under cost and working environment criteria using both qualitative and quantitative data. Alternatives were compared and assigned with ranks using the AHP model. The postal department has adopted ‘Layout 6’, as it is ranked number one as per global weight. Thus, it implemented in April 2018 in NSH Speed Post Centre, Southern India. In this way, the practical implications of the model, as mentioned above could be justified. Also, this model exhibited overall operational performance in terms of production, better working environmental conditions, also housekeeping. This paper used a systematic approach based on AHP, which could be useful in the layout selection process and also the practical usage of time. However, results shown in the postal service sector cannot be generalized in other firms due to requirements of the respective organisations. In the future, researchers can work on this problem in other MCDM methods such as Fuzzy AHP, ANP, TOPSIS, SAW, and DEA for the better result.