Figure 1 shows the annual TEU throughput at the POLA and POLB for the period 1997-2016. Although the explosive growth of the first ten years exhibited a slowdown after the recession of 2008, it has achieved quite a healthy recovery in the last five years reaching or surpassing its pre-recession levels. The numbers in Figure 1 include both loaded and empty units, destined for import or export. Figure 2 shows the change in total annual TEU throughput for the combined ports. The yearly change over the last five years is positive. The total container throughput through the POLA and POLB is expected to grow in the future, correlated with population increase, domestic demand for inexpensive manufactured goods, as well as global demand for US products, and improving competitiveness of US industry. Handling a large number of the necessary container transactions requires intensive management of operations, changes in transportation policy and modernized equipment. In the POLB and POLA, there are approximately 100,000 chassis available for leasing and transporting containers to and from warehouses, stores, factories, rail yards and container terminals. Among these 100,000 chassis available to the trucking companies there are chassis supplied by various third party chassis leasing companies. However, terminals within the ports do not always have chassis available from each company. At times, cannabis grow room chassis required by the trucks are either not available anywhere in the terminal or are dislocated and need to be repositioned. Prior to 2014 chassis companies did not work together or have a neutral chassis pool, and shortages and dislocations of chassis occurred frequently.
Trucks would often be required to travel between terminals and perform additional trips to pick up or drop off chassis at specific locations in addition to picking up and dropping off the containers for export and import. This was a lengthy and cumbersome process and generated additional queues at each terminal. The shortage of chassis can significantly lengthen truck turn times and cause additional cost for trucking companies and increase emissions at the port. Furthermore, lack of chassis could mean that the container will be kept at the carrier ship for prolonged time and the storage fees will continuously accumulate. The shipper will have to pay additional charge for the failure to discharge a container from the carrier ship within the agreed time frame, known as demurrage charge. Also, when containers are not discharged in a timely manner, the shippers will face a congested space in their area of operation. Such an issue would leave the shippers no choice but to rent additional storage area. This would lead to more expensive carrying cost and delayed delivery time. According to POLA/POLB terminal operators and PierPass officials one of the core reasons for port congestion is lack of chassis. At the POLB and POLA trucks are coming from many locations to drop off or pick up containers and chassis, where the freeways that truck drivers must use to access the port are also used heavily by commuters traveling through the densely populated area surrounding Los Angeles. The most heavily used freeway to get to and from the POLB and POLA is California Interstate 710 .
I-710 has for the most part, four lanes, heavily packed with trucks and commuter vehicles during rush hours, causing major congestion problems in the vicinity of the ports. As the American economy expands, there are more demands for commercial operations, increased freight, and increased numbers of foreign commercial partners. These growing factors give rise to recurring congestion at freight bottlenecks, creating a conflict between freight and passenger service. Moreover, as demands for trading partners increase, more freight ships will be docked to the ports. Handling more transactions also means that the ports will have to increase their processing capacity. This increase will undoubtedly cause the entrance to the port and the areas within the port itself to be heavily congested as well. Congestion in and outside of the port is detrimental to the economy of Southern California, as well as to that of the US as a whole. When there is additional congestion, port operators take much longer to unload cargo ships. Supply chains carrying goods through the POLB and POLA can then become slowed to the point where some retailers find it necessary to redirect their goods. The goods are then redirected by sea or air to other ports on the East Coast where they can be further distributed, resulting in reduced income for the surrounding area as well as additional costs for the retailers themselves. The POP is a neutral, interoperable chassis pool that was launched in February 2015, from DCLI, TRAC Intermodal and Flexi-Van, in cooperation with the POLA, POLB and SSA Marine. Their chassis are pooled together to provide a more efficient way of obtaining chassis for trucking companies, which are able to use the chassis from any of the chassis companies interchangeably. Thus, a trucker can pick any chassis from the POP and drop it off at any designed POP storage area without having to worry about returning chassis to the same exact location. Since truckers have access to any chassis, it allows for a smoother operation at the port and fewer inefficiencies in chassis-related operations.
However, the pools still remain commercially independent and are in competition with one another. A third party service provider manages the billing and other proprietary information among these pools. Nonetheless, even with the improved flexibility, interoperability and efficiency which the POP has introduced, the port still suffers some repositioning issues and the heavy traffic congestion problems remain.The concept of Centralized Processing of Chassis was introduced as one method for improving travel times associated with container retrieval. This concept was introduced in Europe as the Chassis Exchange Terminal. In the CET concept, the centralized processing of chassis was defined as an off-dock terminal located close to the port, where trucks would go to retrieve imports or drop-off exports instead of unloading and loading containers at the marine terminal. The first step in the operation with the CET involves a container being loaded onto a chassis at the marine terminal. The second step includes the chassis transport to the CET during off-peak hours, for example at night time. The last step in the operation is when a truck carrying a chassis with a container drives into the CET. At this point, the truck exchanges the chassis it brought into the CET with another chassis and container, grow trays which has already been transported to the CET during the second step. The exchange operation involves unhooking a chassis and hooking up another one at the CET. This is much simpler, more efficient, and a lot faster operation than the operation of unloading and loading containers and performing chassis exchanges at a regular marine terminal .The large volume of container trips results in traffic congestion in the areas around and within the ports and is expected to grow even higher in the future. It is clear that any system which helps reducing the total travel time for trucks between their points of origin and their destinations, is worth investigating, since as a consequence it will reduce traffic congestion, noise and emissions, in addition to saving time for both truckers and port operators. Such systems improve the travel time reliability and help the local economy to grow. By improving travel time reliability, local businesses require fewer operators and less equipment to deliver goods on time and need fewer distribution centers and less inventory to account for unreliable deliveries.Note that among the types of transactions described in Section 0 the Type 1 and Type 2 transactions are the only types which would be anticipated to contribute to a noticeable reduction in total transaction time if a CPF was used. In the case of Type 1 transactions, the export container can be dropped off at the desired marine terminal, and then the chassis can be returned to the CPF for storage and later retrieval. In the case of a Type 2 transaction, the chassis for import can be picked up at the CPF before entering the marine terminal to load the import container. In both cases if the chassis exchange transaction can be done more efficiently when it is performed outside of the marine terminal this could offer improvements in total time for the transaction. In Type 3 and 4 transactions one can see that no chassis exchange activities are necessary. In a Type 3 transaction the wheeled import includes a container already loaded on a chassis and can simply be picked up by the bobtail. In a Type 4 transaction the chassis used for the export container is the same one onto which the import container can be loaded afterwards.
Finally, Type 5 transactions, although they include a chassis exchange, would not be anticipated to have any reduced transaction times using an external CPF. This is due to the fact that after dropping off an export, the bobtail must drop off the chassis used so it can pick up a wheeled import at the same terminal, making in inefficient to travel to an external CPF to drop off the chassis only to return back to the marine terminal to pick up the wheeled import.A representative sample of seventy-one trucking companies which service the POLB and POLA is used in this case study. In order to select this sample, an initial list of TCs was created from an internet drayage directory which includes all companies operating within Los Angeles County. Since the location of the TCs is a critical variable for the optimization problem, all companies whose address was not included in the drayage directory were eliminated from the list. The final list contains all companies with known address using chassis. In the analysis herein the number of daily transactions between marine terminals and trucking companies was assumed to be a fixed value between each trucking company and each marine terminal. In the initial analysis, the number of total daily import transactions was set at 50,000 FEU based on forecasts of total daily port trips. Sensitivity analysis results used 10,000 import and 5,000 FEU export daily transactions based on the average daily import and export container traffic provided in Table 1Table 4.Potential CPF locations were identified by searching for vacant land within a 15-mile radius of the POLA and the POLB. The capacities of these locations were estimated by using the Google earth polygon built-in feature to calculate an approximate square footage. Several CPF layout options and chassis stacking methodologies were evaluated as described in 0. Chassis can be stored vertically or horizontally as shown in Appendix A, and each storage method has its advantages and disadvantages. Among the various possibilities that were considered, horizontal storage layout with a maximum of 3 chassis stacked on top of each other was selected for the case study. Using the estimated square footage, the number of forty-foot chassis which could fit in that area was determined using this preferred chassis layout methodology which assumed allocations for access roads; blocks of stacked chassis ; and blocks of unstacked chassis for ease of access, in order to minimize chassis retrieval times. An example of the layout for a 5000×5000 foot area is included in Figure 8 below. For this example, the maximum number of forty-foot chassis which could be stored in this area was estimated at 170,000. After verifying that the linear program behaved as expected for the two simplified models used in the reduced-node cases, the full model was analyzed using the same approach. In this case, all of the 16 potential CPF locations were included, each with its the estimated chassis storage capacities provided in Table 5. All 71 TCs and 14 MTs are also included with ~50,000 transactions distributed evenly between them . The results are summarized in Figure 12, where it can be seen that when P = 0 seconds, all of the transactions are routed directly from the TCs to the MTs. However, even with a 5-minute increase in efficiency at the CPFs in terms of average chassis retrieval time , approximately half of the transactions are routed through CPFs. The number of transactions that are routed directly from TCs to MTs is decreasing rapidly as the value of the parameter P increases. Figure 12 shows that when P=1200 sec, virtually no transactions are routed directly to marine terminals. Table 14 shows the percent utilization of the CPFs for P = 1200 seconds.