Superior Plus in 12 m radius curve. It is apparent in the drawing how a mechanical coupling connects two middle car sections and their trucks. This mechanical coupling provides minimum yaw angle of truck rotation about the car body, improves significantly guiding forces between wheel and rail and provides the widest car body for TTC Structure Gauge. This mechanical coupling is of simple and reliable design which is proven in the operation of 435 pieces of KT4 streetcar vehicles produced by CKD Prague for many European cities. These vehicles have been in revenue operation for more than 20 years.