Importance and Applications of Robotic and Autonomous Systems (RAS) in Railway Maintenance Sector: A Review <s> RAS in Railway Maintenance <s> Maintenance shops appear to be the most likely locations for robots in the railroad industry. The few robots that railroads have installed are found in shops, and shop activities such as welding, grinding, cleaning, and painting are well-suited to the use of standard robots. The study identifies and evaluates more than two dozen technically feasible applications at Conrail's Juniata locomotive rebuilding shop. Fewer than half showed financial merit, primarily because of the high investment cost and the low potential for labor savings. Proposals to install an automated glass bead blasting booth and an arc welding center were deferred because competing projects had higher returns. In short the application of robotics technology was found to have only a limited potential for improving the productivity of modern railroad shops. As the state-of-the art advances, more applications will be both technically and economically attractive, but the impact on railroad maintenance will likely remain modest until equipment is redesigned to be maintained with simple, inexpensive robots. <s> BIB001 </s> Importance and Applications of Robotic and Autonomous Systems (RAS) in Railway Maintenance Sector: A Review <s> RAS in Railway Maintenance <s> A description is given of a feasibility study which clearly indicated that robotics for undercar cleaning is indeed viable, both technically and economically. The proposed final system will combine water and air cleaning in the existing degreasing bay suitably modified by the addition of a second platform and appropriate walls and doors. Three robots will be used (one in the center and two on the outsides) each on its own track (approximately 60 m long) to permit cleaning a pair of cars at a time. An industrial vision system will be used to detect the exact position of the car and to correct the robots' starting positions on the tracks. The present frequency of cleaning can be achieved in less than two shifts with the proposed system, thus permitting more frequent cleaning and some fleet expansion. Other possible applications of automation to transit vehicle maintenance are also discussed. > <s> BIB002
For decades, researchers have conducted extensive studies to introduce RAS into railway maintenance tasks. For example, in 1987, Martland analysed how robotics could affect the locomotive rebuilding at Conrail's Juniata locomotive rebuilding shop, where he has taken more than two dozen of processes into consideration. Through this study, he has concluded that there is only limited potential for improving the productivity of the rail workshop through RAS and it will remain modest until equipment and technology become economical BIB001 . In contrast, another feasibility study that was conducted by Wiercienski and Leek two years later has concluded that the use of robots to clean the undersides of Toronto subway cars is viable, both technically and economically. They have proposed a system that includes three industrial robots and an industrial vision system to wash undersides of two subway cars simultaneously BIB002 . In this paper, more than 65 authentic research articles that were related to distinct research and developments of RAS in railway maintenance domain have been summarized and analysed. It has been identified that majority of examined developments are related to rolling-stock maintenance and inspection, which is about 56%. About 28% developments are related to rail-track maintenance and inspection tasks, followed by power transmission maintenance, which is around 5%. RAS in the railway bridge and tunnel maintenance accounted 4% and 3% of total developments, while other maintenance applications, such as automated condition monitoring of grade crossings and cleaning of stations and platforms accounted for 4% of the total developments-see Figure 3 . Further, it has been found that the majority of RAS implemented are limited to inspection and monitoring tasks, which are about 62%. The remaining 38% of RAS perform physical manipulation-see Figure 4 for a detailed breakdown by area of application. 