Traffic Congestion is a Risk Factor for the Supply Chain Study Case “ FLORIS Distribution ” in Tunisia

In modern supply chain networks, in order to increase their competitive edge, the firms employ new strategies such as recentring their activities by outsourcing some part of their production, proposing increased diversity of products to capture the market share, focusing on flexibility and responsiveness, with longer paths and shorter clock speeds, today’s leaner, justin-time etc, these strategies augment the vulnerabilities of the firms in an uncertain environment (Gonca, T et al., 2010; Jianxin, X, 2008; Lu, S, 2011).


Introduction
In modern supply chain networks, in order to increase their competitive edge, the firms employ new strategies such as recentring their activities by outsourcing some part of their production, proposing increased diversity of products to capture the market share, focusing on flexibility and responsiveness, with longer paths and shorter clock speeds, today's leaner, justin-time etc, these strategies augment the vulnerabilities of the firms in an uncertain environment (Gonca, T et al., 2010;Jianxin, X, 2008;Lu, S, 2011).
Due to the increasing supply chain complexity, the notion of supply chain risk management has gained an increasing popularity in recent years.
Nowadays, the transportation problems and traffic management risks represent an important challenge for the development and infrastructure use.In this context, it seems important to build up measuring tools for Vehicle Routing Problems (VRP), therefore, we integrate the congestion effect as a supply chain risk management concept, and we will try to measure its impact on environment using a survey.important in this research project is to develop scientific tools that will allow us to evaluate the traffic congestion effect which is considered as a supply chain risk factor.

Supply Chain (SC)
The term supply chain is relatively new addition to the lexicon of management, first used in the early 1980s when writers coined the phrase to describe an emerging management discipline (Peck, H et al., 2003).The literature offers a variety of definitions of supply chain.
According to (Kissani, I , 2008) a supply chain is defined as a network of suppliers, factories, warehouses, and distribution centers through which raw materials are produced, transformed, and delivered to the customer.

Supply Chain Management (SCM)
Supply Chain Management (SCM) is now a fact of life.It is also a dynamic entity that is constantly changing and evolving in response to changes in technology, competitive actions, and customer demands (Melnyk, S et al., 2006), and it is a field of growing interest for both companies and researchers (Bemmel, J.H, 2000).
The literature on SCM is plentiful (Gonca, T et al., 2010), and the definition of supply chain management can be easily found in the research papers (Jianxin, X, 2008).
For (Simchi-Levi, D et al., 2000), Supply Chain Management is the set of approaches used to efficiently integrate suppliers, manufacturers, warehouses and stores so that merchandise is produced and distributed at the right quantity, to the right locations, and at the right time, in order" to minimize system wide costs while , satisfying service level requirements.
By (Gunasekarana, A et al., 2008), SCM is defined as the coordination of resources and the optimization of activities across the value chain to obtain competitive advantages.
The goals of supply chain management are to reduce uncertainty and risks in the supply chain (Guiffrida, AL et al., 2006).
Supply chain management without considering risk issues in a systemic perspective and their impact on the performance measures eventually lead to suboptimal results and inconsistent processes (Gonca, T et al., 2010).

Supply Chain Risk Management
Managing risk in supply chains is an important topic in supply chain management.The topic importance is due to several industry trends currently in place: increase in strategic outsourcing by firms, globalizations of markets, increase reliance on suppliers of specialized capabilities and innovation, reliance on supply networks for competitive advantage, and emergence of information technologies that make it possible to control and coordinate extended supply chains (Lu, S, 2011).
Supply chain risk management has increasingly become a more popular research area recently.Various papers, with different focus and approaches, have been published since a few years ago (Rossi, T, et al., 2006;Iwan, V et al., 2009;Tang, O, 2010).

Literature Review: Congestion is a Supply Chain Risk Factor
It must be at first noted that most researches and studies affirmed that the traffic congestion, characterizing contemporary metropolises, causes repercussions that affect all the society in general and more precisely economic actors (Moustakbal, A, 2009).
And it is, in most, if not all, perceived by residents and businesses as a problem (Blanco, H et al., 2009) Also and according to the federal highway administration in 2006, the costs generated by transport congestion could be as high as 1.5% of GDP in some countries.
For the responsible of logistics, the traffic congestion makes a big problem in the managing of the distribution networks (Moustakbal, A, 2009).Also, worsening traffic congestion has been identified as a supply chain risk factor (McKinnon, A et al., 2008).

Survey Review
In order to evaluate the supply chain features and their effect with environment issue, we have made a survey based on setting the general criteria and the interaction between them.The survey has been shared world-wide throw professionals' websites and by emailing.The survey aims to analyze the environment impact in supply chain researches and daily transport operations.
The editorial questions were based on the literature reviews and previous environmental impact analysis: 1) Do you take into consideration environmental impacts on studying logistic planning and risk management strategies?
2) How do you evaluate the following items (Quality, Time, Cost and Environment) in logistic systems and how important are they to you?
3) How do you evaluate the importance of those characteristics (Agility, Leanness, Responsiveness, Sustainability, Collaboration, and Communication) in logistic systems according to the following aspects (Quality, Time, Cost, Environment and Risk (Congestion))?

Survey Participants
The survey has been answered by 519 professionals, but our study takes into concern only the first 350 participants due to technical constraints.

Results Analysis
The aim of the survey, as sited below, is to examine the current behavior of supply chain with the environmental impact, and to estimate the importance of each criterion.So, using the available website tools, we consider a scale of rating based on having a mark (/6) for each one and for both issues: evaluation of current situation and estimation of the importance.into cities, were all designed decades ago, under different theories of urban traffic measures.Planners still need to deal with the basic problem of congestion and ways of doing so, range from large-scale infrastructure projects to actions as simple as keeping the public well-informed about city route options.

Problem Set
We have made a survey based on vehicle routing schedules dealing with a real-time vehicle routing problem with time windows and simultaneous delivery demands.The measurements are taken during two months with supervision of weekly updating schedules of a "FLORIS Distribution" company in a region of 225 km 2 , with nearly 300000 citizen and five main urban areas and two non-urban areas surrounding the region.We have studied the routing schedule of a simple vehicle responsible for delivering a large quantities of a singular known product and it is weekly updated (each day of the week corresponds to an area of the region).The urban areas are supplied on Monday, Tuesday, Wednesday, Thursday and Saturday.The non-urban areas are both supplied on Friday.
It is important to note that the study focused on a micro scale prototype.Therefore, a comprehensive network analysis is an essential part for modeling a solution to measure the traffic congestion.having a long time to accomplish a common demand orders for short distances.Those curves represent the urban areas, characterised by a high traffic levels.
• A unique curve (Friday), representing the non-urban area, which is characterised by a low traffic level.
The VRP-TW is evaluated to quantify the traffic congestion according to general routing condition.So, it is measured in a partition of time according to the following equation: The previous diagram (Figure 5) represents the "marketing" features which do not illustrate the main effects of traffic congestion.So, we have to define new parameters that enable us to determine the real measure of traffic congestion.Therefore, using a decimal-scale; in a first step we represent the routing parameters in order to demonstrate the performance of each schedule (Figure 6).In a second step we represent the time parameters (Figure 7) to reveal the traffic congestion effect.

Table 1 : Performance Matrix Using
matrices analysis functions, we rate each feature, via a selection of criteria which allow as making reasonable estimations, in order to converge the research to reality.