When judging the performance of a high-speed vehicle on the track, it is ascertained that the following requirements are fulfilled.
(a) At the defective locations in the track, the variations in the vertical and lateral wheel loads should not reach a level where the wheels can get derailed because of the incidence of mounting.
(b) At defective portions of the track, the variations in the vertical and lateral wheel loads should not reach a level where they can lead to derailment as of a result of the distortion to the track.
(c) It should be ensured that the passengers are generally comfortable while the vehicle plies on the track and that goods are carried without any damage.
(d) In the case of diesel and electric locomotives, it is specified that a lateral force lasting more than 2 m should not normally exceed 40% of the axle load plus 2 t. The values of acceleration recorded in the cab at locations should, as far as possible, be limited to 0.3g, both in the vertical and the lateral direction. A peak value of 0.35g may be permitted in case the records do not indicate a significant tendency of this value to be repeated. The ride index is calculated for the purpose of comfort analysis, based on the lateral and vertical acceleration values obtained from acceleration output graphs. The ride index should normally not be greater than 4; a value of 3.75 is preferred.
In the case of carriages, the values of horizontal and lateral accelerations should generally not increase beyond 0.3g, and an occasional value of 0.35g is permissible, as stipulated in the case of locomotives. The value of the ride index should not increase to 3.5, though a value of 3.25 is preferred.