Tyler's report led to an unusual alteration, as it was discovered that the internal width of the overbridges was only , but the railway's passenger carriages were wide, leaving only clearance on either side, which was less than the minimum required clearance of . To alleviate this problem, McConnel proposed that the doors on one side of each carriage be permanently barred and the track slewed off-centre beneath the bridges to allow adequate clearance at least on the side with doors, which would allow passengers to get out of the carriages if the train stopped underneath a bridge. Tyler agreed to this arrangement, and to this day all carriages on the Talyllyn have doors on one side only, an unusual feature for a public railway which is shared (albeit for different reasons) with the neighbouring Corris Railway. Tyler also required that improvements be made to the railway's first two steam locomotives, as locomotive No. 1 suffered from excessive "vertical motion" and No. 2 was said to suffer from "horizontal oscillation". No. 1 was returned to its manufacturer where a set of trailing wheels was added to reduce the rear overhang, and the springs on No. 2 were adjusted and the crank pins shortened to reduce its oscillation.