Conventional pneumatic brake systems used in light rail vehicle have several limitations andrndisadvantages such as the response delay in building up the pressure necessary to actuate thernbrakes there is also, the long time delay between front and rear car, wear of braking pad andrnrequirement for auxiliary components (e.g. compressor, transfer pipes, auxiliary reservoir andrnmain reservoir) increase the overall weight and it is bulky in size of braking system. Thisrnpaper presents an electromechanical brake system for light rail vehicle usingrnmagnetorheological (MR) fluid.rnThe proposed MR brake consists of rotating disks immersed into an MR fluid and anrnenclosed electromagnet. When current is applied to the electromagnet coil, the MR fluidrnsolidifies as its yield stress varies as a function of the magnetic field applied by thernelectromagnet. This controllable yield stress produces shear friction on the rotating disks,rngenerating a retarding braking torque. This type of braking system has the followingrnadvantages: faster response, easy implementation of a new controller or existing controllersrn(e.g. ABS etc.), less maintenance requirements since there is no material wear and lighterrnoverall weight since it does not require the auxiliary components.rnIn this paper practical design criteria such as material selection and MR fluid selection arernconsidered to select a basic MR brake configuration. The mechanical part is modeled usingrnBinghamâ€™s equation, an approach to modeling the magnetic circuit is also proposed in thisrnwork. The equation of the torque transmitted by the MR fluid within the brake is derived,rnbased on this equation, after mathematical manipulation, the torque generating by the MRB isrninvestigated theoretically. The MRB in a rail vehicle was studied using a 1/8th vehicle model.rnThen, a finite element analysis is performed to investigate the resulting structural and heatrndistribution within the MR brake configuration.rnResults shows that MRB generates much lower braking torque compared to that of brakingrntorque required for train to stop and a finite element analysis results shows operatingrntemperature can intermittently reach outside the recommended temperature range of the MRrnfluid, however possible design improvements are suggested to further increase the brakingrntorque capacity and to reduce temperature rise.