Ergonomics improvement in the supply chain. - iea.cc · route per zone for each distribution channel, reaching a total of 35 routes of which: 24 were from the distribution ... 3.1

D. Alvarez and J. Rasmussen / Ergonomics improvement in the supply chain.

Ergonomics improvement in the supply chain.

Authors: Jessica Rasmussen *a, Diana Alvarez *a Co- authors: Shyrle Berrio a, Oscar Bernal a, Leonardo Quintana a

aErgonomics Studies Center, Department of Industrial Engineering, Pontificia Universidad Javeriana, Bogotá,

Cundinamarca, COLOMBIA.

Abstract. Delivery of goods to customers is a fundamental process in the supply chain operation. During this process people perform activities that include manual handling of loads, driving, and customer product delivery among others; these activities are known to be associated with musculoskeletal disorders and work accidents. This research evaluated whether factors like the type of truck, the way the product is delivered and customer conditions of four (4) supply channels can increase the risk of developing musculoskeletal disorders, in addition to determining the most critical activities in driving, warehousing operations and delivery of goods. This evaluation was performed in a Colombian company which distributes dry foods (that does not require cold chain), collecting information from 81 sales assistants in delivery channels, wholesalers, local shops, dealers and supermarkets. Comfort/discomfort questionnaires and observation techniques were used. The results show that the most affected body part is the lower back with 25.96% reporting over 4 in discomfort, on a scale of 1-10 (moderate discomfort), the channel wholesalers is the most critical and driving is the activity with the highest discomfort reported. Alternative options are proposed to improve the delivery conditions. Keywords: Ergonomics, dry food transport, delivery of goods, logistics trucks, musculoskeletal disorder, manual material handling, delivery channels, supply chain. 1. Introduction:

Ergonomics plays a critical role in the maintenance of workers in optimum condition, allowing for the adequate flow of materials and information; when work conditions affect the productivity of the workers, thus affecting the output of the system [1,2]. This is because “As long as ergonomics is taken into account from the planning stage and is less considered as a corrective cost, its scope will be more significant in terms of operational productivity, improving as well the life conditions of workers” [3].

To perform their activities, transporters resort to manual material handling, which is considered as one of the tasks with the largest recoverable loss in the organizations [4]. Additionally, according to studies carried out in the transportation sector, the main occupational diseases are non-traumatic musculoskeletal disorders in neck, back and upper extremities [5]. In regard to accidents, according to a data base of 3,053 cases of labor accident patterns, it was determined that in the United States, the largest amount of accidents happen during the entry and exit of trucks (i.e., slips and falls) and injuries due to excessive efforts (mainly back and spine) as a result of the effort during the handling of loads weighting more than 20 pounds) [5], as well as the exposition to vibrations (to which individuals are exposed during driving), which has been associated to lower back pain, vertebral degeneration and head ache among others [7,8].

This research project started upon the interest of the Corporation (Dry food distribution and trading Colombian Corporation) in including ergonomics in its logistic processes, in order to create healthy work environments, decrease the accident and labor injuries indexes and increase the performance of the Company. Its purpose was to identify possible risk factors associated to musculoskeletal injuries in the transportation of dry foods (that does not require cold chain) in the site in Bogota. 2. Methodology

2.1. Study design The study is divided in four stages: the understanding and knowledge of the transportation process, the application of questionnaires, the application of observation techniques and the formulation of solution alternatives.


2.2. First stage: Understanding and knowledge of the transportation process The study included 81 Colombian males, who transport food for the company, with ages ranging from 18 to 58 years old, and a 10 year average time performing similar work. Their daily activities include the transportation of a loaded truck with the products to be delivered to every customer, get the order ready for every customer, packed in bags or boxes upon request from the client (the products are separated and transported in containers), delivery of the orders (in bags or boxes, the complete product or in a container), verification that each order is complete. A visit to the company was performed initially, a protocol to gather information was established with the tools to be implemented and a pilot test was carried out by accompanying six routes during a complete week, applying the established questionnaires. A general information form was devised to register the demographic variables; together with a route characterization questionnaire including data such as the total weight of the merchandise and the number of daily orders; a customer characterization questionnaire with data on the delivery mode and conditions of the customer; and finally, a comfort/discomfort questionnaire or Nordic Questionnaire (self-report questionnaire) [9]. 2.3. Second Stage: Application of Questionnaires The technique of intentional sampling or convenience sampling was used to select the routes, choosing only one route per zone for each distribution channel, reaching a total of 35 routes of which: 24 were from the distribution channel known as Local Shops (distributing merchandise in small neighborhood shops), 4 in the wholesalers channel (wholesalers orders), 4 in the supermarket channel (self-service stores) and 3 in the dealers channel (orders from small distributor companies, the delivery mode is different from all the others as hydraulic jacks are used). The selected routes were accompanied for a full time shift, 5 days a week. The Nordic questionnaire was applied every day at the start, middle and end of the shift. The other questionnaires were applied once a day. The information was collected for a period of 8 weeks. With a trust level of 90% and an error margin of 5%, it was estimated that a total of 78 individuals should be included in order for the survey to be representative. In this case 81 persons were included of a total of 148 workers (participation level 54.73%).

For data analysis, the collected information was unified and refined in a Microsoft Spread Sheet. The average report of discomfort per person for the start, middle and end of a shift was estimated, per the 5 days of the week. Then, the percentage of discomfort reports larger or equal to 4, for each body part, by channel and work shift was calculated, based upon a pain perception criteria [10]. Colors were chosen and used (described in Table 1), in a human body outline, per channel and activity (loading at site/delivery/driving).

Table 1. Colors assigned by the percentage of reports of discomfort.

Color Low Medium High Very high

Frequency Less than 10% Between 10% and 20% Between 20% and 30% More than 30%

2.4. Third Stage: Application of observation techniques The sampling of 22 research subjects was divided as follows: 1 worker of the dealer channel, 1 of the supermarket channel, 6 workers from the wholesaler channel and 15 of the local shops channel. These workers were accompanied in each of their routes, filming for 45 minutes the tasks performed along the day shift, during two weeks. Then with the help of the ergonomics observation tools OWAS and REBA [11], the resulting videos were observed and analyzed and the results compared by person/activity/ task, identifying the most critical tasks per activity in each channel and the part of the body most affected. 2.5. Fourth Stage: Formulation of solution alternatives A Focus Group with professionals and experts was formed, where problems were discussed and solutions were formulated, describing main advantages and disadvantages and defining critical body parts that will benefit with the implementation of the improvement proposals. Human Hazop techniques were used to identify critical points and detect the human operational risks by using the logic frame (EML) approach as a brain storm methodology and technique, in order to propose possible solutions according to the issues discussed by the group. [12,13].


3. Findings

3.1. Comfort/Discomfort Questionnaire Table 2 show the outline of the human body according to the final reports of discomfort for the activities of getting the orders ready and delivery in each channel. Also Table 3 shows the behavior of the most critical parts of the body through the week. On the other hand, Table 4 shows the highest discomfort reports per driver and second driver by channel and Table 5 shows the discomfort reports per driver and second driver according to the truck type (Chevrolet). Table 2. Outline of the human body according to the final reports of discomfort.

Local Shops Supermarkets Wholesalers Dealers Discomfort

Reports Loading

Discomfort Reports

Delivering

Discomfort Reports Loading

Discomfort Reports

Delivering


Discomfort Reports

Delivering


Discomfort Reports

Delivering

Table 3. Behavior reports discomfort in critical body parts.

Channel Discomfort Reports Loading Discomfort Reports Delivering

Loca

l Sho

ps

Sup

erm

arke

ts

Who

lesa

lers

0.0 5.0

10.0

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

Monday Tuesday Wednesday Thursday Friday

Upper Back Low Back

0.0 5.0

10.0

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End


Low Back Feet

0.0 2.0 4.0 6.0 8.0

10.0

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End


Upper Back

0.0 2.0 4.0 6.0 8.0

10.0

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End


Lower Back

0.0

5.0

10.0

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End


Upper Back Thighs

0.0

5.0

10.0

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End


Low Back Feet


Dea

lers

Table 4. Discomfort reports by channel

Upper Back

Lower Back Thighs Knees Feet R.Sho

ulder Dealers 0% 19% 17% 25% 33% 0%

Supermarket 10% 10% 2% 0% 0% 0% Wholesalers 21% 27% 23% 15% 29% 21% D

river

Local shops 24% 53% 15% 20% 26% 30% Dealers 0% 0% 3% 3% 23% 0%

Supermarket 2% 11% 0% 0% 6% 0% Wholesalers 19% 31% 14% 10% 25% 8% S

econ

d D

river

Local shops 18% 32% 13% 15% 22% 20%

Table 5. Discomfort reports by truck type.

Upper Back

Lower Back Thighs Knees Feets Right

Shoulder

FRR 50% 50% 0% 0% 0% 0% FTR 0% 0% 0% 0% 0% 0% NHR 7% 7% 7% 7% 7% 20% NKR 32% 50% 21% 23% 33% 32% D

river

NPR 17% 42% 13% 18% 25% 21% FRR 0% 22% 0% 0% 0% 0% FTR 0% 0% 7% 0% 13% 0% NHR 7% 7% 20% 7% 13% 13% NKR 30% 39% 25% 23% 37% 23% S

econ

d D

river

NPR 12% 26% 7% 9% 17% 13%

3.1.1. Common factor in all channels An increase in discomfort is observed at the end of the shift per day and when the day changes, it decreases again. It is also seen that the discomfort report is lower at the beginning of the week as compared to the end of the week. When evaluating the trends of straight lines surging when discomfort reports of body parts are put in a graphic along a week (discomfort vs the day of the week), a positive trend was found (β>0) and Pearson correlation coefficients (Goodness of Fit with strong correlation coefficients higher than 0.8 in critical body parts), that is to say that the discomfort report increases as the week progresses.

In regard to the type of truck, it can be seen that the NKR and in less measurement the NPR, are the trucks with the largest percentage amount of discomfort reports and that in most of the trucks it is the driver who reports more discomfort as compared to the second driver. 3.1.2. Critical activities

The most critical activity in all channels is loading orders, where the lower back, thighs and feet are the most affected body parts reported. The other critical activity is driving where the back, the lower back and the feet are the most affected body parts reported. 3.1.3. Variables taken into account

It is observed that at shift starting the first day of the week, the lower back reported a medium-low level of discomfort, therefore variables that could influence these reports were taken into account. A correlation between discomfort and the variable “period of time in similar tasks” was carried out and no relationship was found. That is to say that the discomfort report does not depend on the time the workers have performed transportation tasks, neither was found relationship between discomfort report and workers ages. 3.2. Route and client characterization questionnaires

0.0 2.0 4.0 6.0 8.0

10.0

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End


Feet

0 2 4 6 8

10

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End

1. Begining

2. M

iddle

3. End


Feet


Table 6 show the information gather for each channels, i.e., average number of orders, average load per truck and average daily working time.

Table 6. Route questionnaire results.

Local shops Supermarkets Wholesalers Dealers

Average # of orders delivered by each route per day 55 orders 3 orders 11 orders 1 order

Average load carried by each route per day 780,99 Kg 1.973,47 Kg 2.374,18 Kg 5.302,43 Kg

Average daily working time 7 h and 52 m 8 h and 35 m 7 h and 50 m 9 h and 25 m

Table 7 show variables related with the location where the workers deliver the orders, the conditions requested by customers, the delivery mode and the percentage of occurrence of each variable (the most predominant is shown).

Table 7. Client characterization questionnaire results.

Location Channel

Loading Access Conditions of the

customer Delivery mode

Dealers 83% In warehouse with stacker 80%

They have slippery floors, uneven, with

stairs and ramps 80% Client delayed 72% Full product

(stowed)

Supermarkets 58% On the floor 51% Narrow entrances, stairs and ramps 48% Client delayed 54% Repackaged

product

Wholesalers 40% On the floor of the warehouse 39% They have narrow

access 41% Client delayed 60% Full Product

Local shops 83% On the floor 41% They have narrow access 66%

Client delayed and unsafe

area 77% Repackaged

product

According to the percentages, the dealer channel and the supermarkets are those with the most inappropriate condition for the delivery of the orders. It is also noted that in channels where the product is re-packed (loading), high discomfort reports in the upper back and in the lower back are shown when the activity is carried out on the floor.

Figure 1. Delivery mode (plastic bag, full product,

container)

Figure 2. Access to shops upper floors

3.3. Observation Techniques Table 8 below, shows the summary of the results obtained for each activity in every channel and each observation tool used, mentioning the body parts and the critical tasks. To get an idea of postural conditions of workers, figure 3 shows in overall terms how is the delivery of the orders.


Table 8. OWAS and REBA analysis results.

Channel Activity OWAS Postural Condition REBA Postural Condition

-It is required to take immediate corrective actions in legs and back.

-It is required to take immediate corrective actions in arms, trunk and legs.

Loading -Critical Task(s): Loading in box, place the products at the door of the truck.

-Critical Task(s): loading in boxes and bags. Search for the proper container.


-It is required to take immediate corrective actions in trunk, arms and legs. Lo

cal s

hops

Delivery -Critical Task(s): Driving to the client’s with the order, unload the order at delivery site. -Critical Task(s): Unload the order at delivery site.


-It is required to take immediate corrective actions in trunk and arms.

Sup

erm

arke

ts

Delivery -Critical Task(s): Unload the order at delivery site and organize empty containers.

-Critical Task(s): Load the empty container in the truck, unload the order at delivery site and organize empty containers.

-It is required to take immediate corrective actions in legs, arms and back.

-It is required to take immediate corrective actions in arms and trunk.

Loading -Critical Task(s): Find, take and pile the product in the truck for delivery.

-Critical Task(s): Find, take and pile the product in the truck for delivery.

-It is required to take immediate corrective actions in legs, arms and back.

-It is required to take immediate corrective actions in arms. W

hole

sale

rs

Delivery -Critical Task(s): Driving to the client’s with the order -Critical Task(s): Driving to the client’s with the order

-It is required to take corrective actions as soon as possible in legs.

-It is required to take corrective actions as soon as possible in trunk and neck.

Loading -Critical Task(s): Place the jack on the platform. -Critical Task(s): Place the jack on the platform.

-It is required to take corrective actions as soon as possible in legs.

-It is required to take corrective actions as soon as possible in trunk and neck.

Dea

lers

Delivery -Critical Task(s): Place the jack on the platform. -Critical Task(s): Place the jack on the platform

Figure 3. Delivery of the orders (Loading, displacement and delivering, review order)

4. Formulation of solution alternatives

Some assumptions that must be subject to testing and then validate them in reality are listed below. ● Install an ascent and descent ladder opening when door opens. ● Periodic training on load handling. ● Physical condition improving program. ● Containers without lids with the possibility of piling, in order to diminish weight. ● Place an inside bag in the container so to enable the filled bag to come out and eliminate the task of re-

packing or getting customers’ orders ready. ● Place the labels on the side in order to visualize them quickly and avoid moving the containers in search of

the customer’s and invoice information.


● Train the distribution center workers to load the truck in an orderly manner and implement color codes to facilitate visual detection, taking into account variables such as weight and customers’ orders organization.

● Devise a special load-unload tool (a tool with ergocart system, varies superficial height according to weight on top, to prevent the worker from bending when taking out the order from the truck, driving and delivery) [14].

● Place racks in the truck according to the type of customer. ● Prevent the workers from getting on and taking off constantly from the truck and avoid the frequent search of

the orders or containers inside the truck. The redesign of the trucks is proposed with doors folding up and with divisions both vertical and horizontal in order to locate the products in an orderly way.

Figure 4. Example of the proposed truck.

5. Discussion

From the beginning of the analysis of working conditions, it was expected that the supermarket channel would report more discomfort, taking into account the levels of manual handling loads daily, (average 1.973,47 Kg), without any mechanical help, as compared to channels, such as that of the dealers with higher loading levels (average 5.302,43 Kg), but handled with hydraulic jacks and additionally with less number of orders. During the accompanying in the routes, the physical effort in the supermarkets channel was found higher than that of the dealers, but the results of the discomfort reports show more discomfort in the dealers’ channel. This result might be related to the type of association and disposition to collaborate from the personnel involved (the supermarket workers are more reserved and careful with the information provided). 6. Conclusions

The most critical channels are Local Shops and Wholesalers. It was observed that in the Wholesalers channel the discomfort reports in the upper back are higher than 20%, and they are possible associated with the larger quantities of products the worker has to displace. To comply with his work, the worker has to place heavy amounts of merchandise on his back, making several trips to and from the truck, until the full delivery of the order is accomplished. As found in scientific literature, it is the back the most affected area of the body in the activity of transportation of merchandise. The high report on feet discomfort might be associated to the amount of walking involved in the delivery of products in the Wholesalers channel. Probably the high report of discomfort in the lower back is due to the lifting of loads where the back is flexed, with the gravity center in the lumbar area, thus generating excessive effort in the lower back. The handling of the loads and the amount of daily orders might be the factors increasing the discomfort reports in the lower back due to the manual handling of loads in the local shop and wholesalers channels. With the second level results (OWAS and REBA), the critical body parts in each channel and the possible causes of discomfort were confirmed (critical tasks and what is implied when executing them).

The loading activity is the most critical task in all channels. The workers getting the orders ready are those that perform movements to find the products inside the truck and repack and/or locate products for the worker delivering them. The current design of the truck serving channels such as local shops, supermarkets and wholesalers obliges the workers to get on and off the trucks several times, and on occasions they do not do it in the proper way. Also, moving the merchandise around several times a day in order to find the required order, is the result of lack of orderly organization in the loading on the part of the distribution center, thus generating more effort and bad postures.

The delivery on the floor is the most common factor in the delivery of orders and it generates bad postures in the deliveryman, produced by narrow accesses, uneven floors, ramps and stairs, which were the most frequent issues found in the current access to customers, with the possibility of accidents and injuries.


In trucks, the motor is placed under the driver’s seat which result according to scientific literature in upper and lower back pain and head ache due to vibrations. According to the findings of this study, reports of high discomfort drivers may be related to exposure to vibration while driving; the truck that produces more discomfort is Chevrolet NKR.

7. References

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Documents

Ergonomics improvement in the supply chain. - iea.cc · route per zone for each distribution channel, reaching a total of 35 routes of which: 24 were from the distribution ... 3.1