3. Systematic Method for the Improvement of Road Transport Operations The method proposed to improve road transport operations consists of the systematic conduction of the four general stages illustrated in Figure 3. The initial/first stage comprises the analysis of a road vehicle’s flow as well as the activities associated with its transport operations. To achieve this, the proposed method suggests conducting an analysis of the value stream of the road transportation operations through a TVSM study (Villarreal, 2012). The study of the value stream of manufacturing (e.g. Seth and Gupta, 2005; Singh and Sharma, 2009), service (e.g. Barber and Tietje, 2008), healthcare (e.g. Teichgräber and de Bucourt, 2012; Lumus et al., 2006) and environmental (Kurdve et al., 2011) operations supported by the traditional VSM (Rother and Shook, 2003) has been widely documented in the academic literature. However, evidence of the use of VSM to support the analysis of the value stream of logistics and transport operations is almost non-existent in the academic literature, with only a handful of articles considering it (Villarreal et al., 2013; Villarreal, 2012; Villarreal et al., 2012; Hines et al., 1999; Jones et al., 1997). Thus, besides proposing an alternative systematic method to improve road transport operations, this article also contributes to the current limited body of knowledge on the application of VSM in the logistics and transport sector. In this case, the TVSM will concentrate on identifying waste related to transport efficiency (Villarreal et al., 2012). The TVSM should consider the complete distribution cycle from picking and loading product orders to the transportation vehicles, to unloading product returns from the market and closing administratively the route or shipment.
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Figure 3. Stages of the proposed systematic method to improve road transport operations
The TVSM analysis can be structured in two parts; one that includes activities pre and post transport and serving clients; and another that considers the physical distribution of the product. The first set of activities is called Not-In-Transit (NIT) activities, whereas the second is known as In-Transit (IT) activities. NIT activities should be executed by warehouse operators while vehicle drivers should focus on performing IT activities only. The information included in the TVSM for NIT activities is the same as that of a traditional VSM as established by Rother and Shook (2003), namely; cycle time, value added time, uptime and setup time. NIT activities should align to the takt time required to load customer orders to trucks and deliver them on time. In the case of IT activities, the TVSM analysis requires specific data that include; average time between clients, truck capacity utilisation level, average distance travelled per client, distance travelled in excess per route, and the percentage of waiting time in transit. On the other hand, for serving clients; cycle time, value added time, the average number of clients per route, the percentage of clients not served, and the percentage of product returns are the main data that should be gathered for the TVSM analysis.
The TVSM analysis will enrich and contribute to the identification of the relevant STEWs (Sternberg et al., 2013) in the second stage of the proposed method. The third stage has the objective of formulating strategies and initiatives to eliminate the STEWs (Sternberg et al., 2013) identified in the previous stage. Improvement initiatives and strategies may include lot splitting, the application of order consolidation, and sequencing initiatives that would impact the utilisation of the transportation capacity and/or reduce the distance travelled to satisfy customers (Villarreal et al., 2009; La Londe and Masters 1994; Burns et al., 1985; Cooper, 1983). Finally, the last phase concerns the implementation of the initiatives and a follow-up of results.
The systematic method proposed can support wider road transportation improvement programmes (i.e. kaizen programmes), for example, those conducted under the umbrella of the Deming’s continuous learning and improvement model PDCA (Deming, 1993). This model has been used as a continuous feedback loop for the improvement of products and processes based on four steps: Plan (P), Do (D), Check (C) and Act (A). The “Plan” step covers activities related to the definition of the problem and the desired state, data collection, identification of root causes, the definition, evaluation and selection of the best solution alternatives, and finally, the scheduling and planning of the required resources for the implementation. The “Do” phase concerns the implementation of the selected initiatives. The last two steps of the PDCA model (i.e. Control and Act) are oriented to determine if the expected results were achieved and to ensure that these are maintained.
In a road transportation improvement programme, the proposed method would support and be aligned to the first two phases of the PDCA model; Plan and Do. In this case, stages 1 to 3 of the proposed method would be part of the “Plan” phase, whereas the last stage would be included in the “Do” phase. Therefore, if one would decide to apply the PDCA cycle for improving road transport operations, the recommended method may be used during the initial two stages of the model.
4. Case Study Implementation and Results This section presents a case study where the proposed systematic lean method to improve transport operations has been deployed, in the distribution operations of a large Mexican organisation, to explore its effectiveness. Woodside (2010) and Cameron and Price (2009) consider a single detailed case study as a valid research methodology, particularly when the study is applicable and suitable for the organisation where the research occurs. The use of a single case study has been well accepted, in recent times, in the academic literature as a valid research method. This is evident from the high volume of recent researches published using a single case study research method (e.g. Bouzon et al. 2015; Bevilacqua et al., 2015; Tuli and Shankar, 2015; among others). Even though a single case study might be considered as a limited approach to prove the effectiveness of the proposed systematic method, if it is replicated again in this and/or different industrial context, a generalisation and validation of findings can be achieved (Garza-Reyes et al., 2014; Yin, 2012). Thus, it would fall in the future research agenda to test the proposed systematic lean transportation method through the use of multiple cases study in different settings.
The Mexican organisation has a primary distribution network which transports frozen and refrigerated products from plants to Central Distribution Centres (CDCs), and from these to Regional Distribution Centres (RDCs). It also includes a secondary network that takes the goods from the RDCs to retailing points or stores. The primary network includes thirteen plants, five CDCs and seventy four RDCs located across México. It is divided into five geographical regions. This paper is concerned with the application of the proposed systematic method on the North-eastern region. This zone accounts for 15% of the total national demand with sixteen RDCs. The firm started an effort to reduce distribution cost in its primary distribution network in 2009. A summary of this initiative is described in Villarreal et al. (2009). To further reduce distribution cost and increase customer service in the secondary distribution network, the studied organisation decided to undertake an improvement project adopting the systematic lean transportation method proposed in this paper. In particular, the improvement project focused on the routing operations from the Escobedo Distribution Centre (DC) to its customers.
The first step of the proposed systematic lean method consists of conducting a TVSM analysis to map the transportation processes of interest. The current macro level TVSM for the routing operations is shown in Figure 4. It was constructed with information gathered from an administrative information system supported by the truck’s GPS and drivers’ handhelds. Additionally, a team of researchers collected detailed field data by accompanying the truck driving crews. This was done by sampling 30% of the routes. The transportation operations mapped consisted of the following activities:
Preparation of routes: This step included the inspection of the orders and truck’s load as well as reviewing the route;
Distribution of products (i.e. transporting products, serving customers and collecting spoiled products);
Returning back to the DC;
Closing routes: This stage included settling payments from customers with the cashiers and returning spoiled product and the truck.
The TVSM study indicated that the average journey time for the distribution of goods from the Escobedo DC to its corresponding retailing stores was 11.8 hrs, see Figure 4. All the activities included in the process, from preparing the routes and serving the stores until closing every route, were executed during the journey. The TVSM analysis also indicated that the average IT time was 9.9 hrs (83.8%), leaving only 2 hrs, on average, for the truck and driving crew to spend on NIT activities executed in the DC.
Figure 4. Macro level of TVSM for Escobedo routing operations
4.2. Stage 2. Identification of STEWs
The second stage in the systematic lean transportation method proposed consists of the identification of the relevant STEWs (Sternberg et al., 2013). Table 2 presents a summary of the most important STEWs identified through the TVSM analysis as well as the processes where they were associated to and how they affected the transport operation.