Evaluation - Validation and Design Analysis Light Rail Transit

Question: Describe about the Evaluation, Validation and Design Analysis for Light Rail Transit. Answer: Introduction As cities continue to increase both in size and population, the available transport systems are increasingly becoming under pressure as their design capacities are overrun. In addition to that, a higher level of pollution from the larger number of the automobile becomes a concern to both the public and the authorities. This has prompted various governments to come up with a solution inform of Light Rail Vehicles (LRV), which can carry a higher number of passengers thereby significantly reducing the higher number of vehicles on the road. Besides, the LRV are environmentally friendly as they rely on electrical energy other than fossil fuels. For most developing nations, this has proven to be a preferred and attractive option for urban public transport. However, just because LRV or Light Rail Networks (LRN) has proved to be successful in other countries does not guarantee that it will work anywhere. The success of any LRN project lies from how the project will be handled from feasibilit y studies, planning, designing, testing, and commissioning, evaluation, validation and human factors among other activities of the entire project lifecycle. All these activities need to be managed properly to achieve the goals of the LRN and minimize or eliminate extra costs during the operation and maintenance of the railroads. This report, in particular, will address the testing, evaluation, and validation of the LRN in addition to looking at how design can be optimized to improve the reliability and maintenance, aside from the human factors. Light Rail System Testing Evaluation and Validation Sharma (2011) points out that the Testing and Commissioning (TC) of a light rail system starts after the concept and detailed design phase. The primary purpose of TC is to ensure that the technical and project requirements are met, and this can be done parallel to evaluation and validation. For testing to be successful, it is vital to involve the employer (owner of the infrastructure), the contractor (and sub-contractors if any), manufacturers or suppliers of the equipment, the railway operator, and to an extent, though not compulsory, a third party organization outside the main contract. As Sharma (2011) states, it is the responsibility of the employer to provide the basic framework outlining the TC process and who is responsible for overseeing it. The contractor will then develop a detailed test plan that defines all the rail systems, their interfaces, tests to be carried out, and the expected results according to the employer and the approval bodies. The test plan also defines the reporting and authorizing procedures for all tests, the schedule, resources (equipment/staff) required for each test, the safety, and documentation for all tests carried out. The ideal model employed during the TC is the FAT-SIT-SAT-SATOV, simply split into four stages namely: Factory Acceptance/Inspection Test (FAT), Site Installation Test (SIT), Site Acceptance Test (SAT), and Overall Site Acceptance/Performance Test (SATOV). Factory Acceptance/Inspection Test (FAT) In this stage, all the light rail equipment and components are tested at the factory/manufacturers site during the production. This is meant to ensure that the equipment and components meet the specifications and requirements for the design and overall project. Tests of all equipment are carried out concerning the systems software and hardware (Sharma, 2011). When it comes to hardware, there are two forms of tests that the contractor is required to perform routine and type tests. In a routine test, each piece of hardware component or equipment is tested independently. Some of the tests could include checking for dimension, insulation, electrical conductivity, mechanical, calibration, hydraulic, and visual inspection among other compliance tests before the equipment is released to the contractor. On the other hand, type tests are done on the complete equipment of a given type or rating according to the set standards or technical specifications as stated out in the contract. In most ca ses, these form of hardware test include testing the mechanical strength of the hardware, the electrical characteristics, compatibility of the electromagnetics just to mention a few. For every software system like vehicle detection system, line signaling, or supervisory control, it is recommended that a test bench should be used to simulate the inputs and outputs in an environment matching the real operation environment. Furthermore, integration testing of all the rail system should be carried out at the factory site to minimize or eliminate possible integration risks of equipment during the assembly at the construction site. Site Installation Test (SIT) Here tests are done on equipment after their installation on the site. The purpose of SIT is to ensure that all sub-systems or equipment are installed and wired correctly and that they can perform the intended operation without any damage after the installation. The tests can be performed in phases on a site by site basis as the various sections of the railway line get built. Not that the sections can be defined as per the infrastructure or line constraints like crossover locations, track layout, overhead contact system, or the location of the sub-stations (Sharma, 2011). For train onboard equipment, SIT must be conducted on the train both at the manufacturers and the employers site. Examples of tests carried out in this stage include stand-alone operation tests, electrical conductivity and insulation, and data exchange or communication tests. Site Acceptance Test (SAT) SAT, considered as a pre-commissioning stage, is done when all equipment and sub-systems have been installed to identify and minimize the modification and related costs at a later date. It is more of an integration test. It is of the utmost importance to demonstrate that all the functional and performance requirements are met. This stage can be sub-divided into SAT-internal and SAT-external. According to Sharma (2011), in SAT-internal, all the systems are put under a pre-defined scope whereas in SAT-external at least one of the system to undergo integration test lies outside the predefined scope. This can be based on the complexity of the relationship or interface of the project with other third parties, the type of contract or the contractors or sub-contractors involved. Just like in SIT, tests for onboard train systems like vehicle detection system are done at this stage. Overall Site Acceptance/Performance Test (SATOV) The goal of this test is to ascertain that the entire system will operate accordingly and offered the required service without any hiccup. The railway operator in addition to all project parties must be involved in this stage as all the functional requirements of the system and equipment when in service are to be tested. The tests in this instance can be split into SATOV-Equipment tests done on all equipment supplied to the project and SATOV-Line which are tests done on the equipment or system when in actual train running for a given trial period. Usually, the SATOV-Line is a responsibility of the employer and the railway operator with technical support from the contractor. Some of the tests conducted in this stage include the full load tests, functional tests, degraded mode, and endurance tests. From these results, employers or contractors can be able to evaluate the actual performance of the system in relation to requirements and expectations outlined in the contract. Once the syst em has passed all the tests and evaluation, the contractors can now hand over the railway system to the employer and operator. Optimization in design and operations of Light Rail Transit (LRT) According to Twum and Aspinwall (2013), reliability is a measure of the ability of the system to carry out its intended function without fail for a particular period in a given pre-determined conditions. Reliability has far reaching consequences on the availability, durability, and life-cycle cost of a system. For this reason, engineers are required to make informed decisions on the components and design configurations that are to be used in a system (Selvik and Aven, 2011). In order to optimize the design and operations for reliability and maintenance of LRT, it is vital to identify first the factors which can impact on the efficiency and effectiveness of the LRT namely: route design, right-of-way (ROW), and track layout and configuration. The design of the LRT is most likely to affect the reliability of operations and impact on the ridership regarding the number of passengers opting for LRT. Given that most urban centers opt for LRT for public transportation so as to reduce traffic congestion and minimize automobile pollution, it is recommended that LRT routes should connect high activity regions along major corridors, highways, and arterials (LRT: Light Rail Transit Service Guidelines, 2007). These regions could include airports, employment centers, shopping centers, education institutions, or high-density residential areas. In cases where new LRT lines are to be developed, the new lines should intersect with old lines so as to enable multiple transfer opportunities for light rail cars. The type of ROW has a significant influence on the operation and speed of the LRT system given that in urban areas they have to interact or crisscross with pedestrians and other means of transport. To improve LRTs reliability, safety, and operating speed, LRT should operate within designated semi/fully-exclusive ROWs. Also, in areas where there are shared ROWs, Li et al. (2007) propose the use of a Mixed-integer quadratic programming (MIQP) model for signal timing at rail intersections to reduce traffic delays and its impact on LRT and other traffic. About track layout and configuration for reliability, double tracking is touted as an optimal operation environment. This is because it allows for bi-directional LRT lines to operate simultaneously along the same segment of the track while at the same time allow for bypassing of stationary or disabled trains at switches and crossovers. Besides, compared to ballasted tracks, non-ballasted (slabs) LRT tracks which have advantages such as l ower maintenance cost and requirements, increased durability (service life), and high lateral track resistance that permits the increase of speed in future is favored (Fazhou Wang and Yunpeng Liu, 2012; Ć iroviĆ¡ et al., 2014). Maintainability According to Langford (2007), system maintainability refers to the measure of its ability to be restored to the usual operational level after a planned or unplanned interruption within a given time using the available resources. This maintainability is mostly considered as design related and is usually carried out to give estimates of system maintenance, downtime, and resources required to carry out maintenance. This will help in optimization or reduction of the time and cost of maintenance works. Note that maintenance can be either corrective which are the unplanned actions to restore system performance after a failure or preventive maintenance which are planned actions to maintain or improve a system performance. In that regard, maintainability is usually measured by Mean Time to Repair (MTTR), Mean Time Between Maintenance (MTBM), and Mean Time Between Failure (MBTF). MTTR is the average amount of time it will take to repair a system and restore services. It is used to calculate maintainability in corrective maintenance. Mathematically, this can be expressed as the total maintenance time divided by the number of repairs conducted over a given period. Langford (2007) points out that we can determine the probability of carrying out repairs within a specified time by using the following formula: M(t) = 1 e-t/MTTR This is critical for reliability or maintenance engineers as it helps them decide whether to replace or repair a system or optimize the maintenance schedules. In the end, this will impact on the availability of system, in this case the LRT, when maintenance is carried out. On the other hand, MTBM is the average time between maintenance actions in consideration of the meant time between corrective maintenance (MTBMct) and the mean time between preventive maintenance (MTBMpt). Langford gives the following mathematical expression: Figure 1 MTBM MTBF is also a measure used by engineers during the design to enhance safety of systems and equipment thereby giving an indication of their performance, reliability, and availability. It is the mean time between recorded system failures. MTBF can be determined by calculating the mean of the difference between start of system downtime and uptime and diving the results by the number of failures as shown below. Figure 2 MTBF This is useful in projecting the likelihood of a particular equipment or system to break down with a given time interval. Human factors in designing concepts Human factor is considered as a discipline whereby knowledge generated by ergonomics, psychology, physiology, and sociology are applied in the improvement of the interaction between humans and technological systems. Its purpose is to understand the capabilities and limitations of the human beings and implement these findings into developing more safer and efficient technological systems. They play a significant role in transportation systems concerning customer experience, safety, operations, and maintenance. Due to this, any designer must treat human factors as an important element in the design process. According to Naumann et al. (2013) and Wilson et al. (2012), railway system designs have to consider human operators as a key impact factor in its operations. Some of the human aspects of the workplaces relating to the design of systems that should be looked into include the perception, communication, attention distribution, cognition processes and overload, vigilance, reaction to stressful situations among others. Even with the current high level of automation in railway systems, train drivers, system operators, and traffic operators still, play a key role in the provision of vital information in designing systems. Wilson et al. (2012) further note that when it comes to light rail systems, there is a higher workload and stressful situations for train drivers given the characteristics of suburban and urban areas. In these areas, there is a high number of train stops, sharing of platforms with other transportation means, interaction with passengers, etc. that could affect the concentr ation of the drivers. For this reason, it requires that the systems should be designed with much care. According to Wilson et al. (2012), given the implementation of on-board information systems in new urban rolling stocks that monitors and warns the driver on the status of the train, this at times causes high workload. As a result, the design and assessment of on board information systems should be based on cognitive design guidelines. In addition, given that rail cars at some points share the platforms with pedestrians as well as vehicles, it is recommended that the design of the cab should provide good visibility as per the driver anthropometrics via the windscreen to improve on early detection of danger and reaction to emergency cases. Furthermore, ergonomic assessment in the evaluation of the visibility, posture, and workplace health risk in addition to the use of heuristic models in the evaluation of human machine interface is vital in designing safe rail systems. As Rail Engineer state, even though humans can be good at adapting to different circumstances by rapid thinking and reaction, they are not best placed in handling the stress and work overload in emergency situations where immediate intervention is requisite. So as to ensure that these issues are addressed, it is essential that all aspects of the Human Machine Interface during the design phase are considered to recognize their impact on system function and performance. This can be achieved by designers by conducting interviews, administering question, or prototype assessment with all railway operators who will provide concrete feedback required to design efficient systems that are easy to operate with high performance (Schwencke et al., 2013). Conclusion and recommendation Light Rail Transit are increasingly being adopted by cities as a solution to traffic congestion in most urban areas given the high passenger capacity and high speed. In addition, compared to automobiles, there are fewer accidents or fatalities recorded of the LRTs. Besides, their eco-friendly nature is making them more attractive to environmental conscious cities. However, successful implementation of the LRTs projects requires extensive design processes that factor in the human factors to make them more reliable and safe. As discussed, it is, therefore, vital that system testing and evaluation should be performed on all components and equipment. This will help reduce addition costs that could arise due to faulty components or accidents. The testing and commissioning of such projects should strictly adhere to the FAT-SIT-SAT-SATOV model as previously discussed. In reference to operations optimization for the reliability of LRT, as a recommendation, an extensive analysis or feasibilit y on the areas where the light rail network will pass. 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