Trends in Turnout Design on Indian
The main factors responsible for
low speeds over turnouts on Indian Railways are as follows.
(a) A sudden
change in the direction of the running edge upon entry onto the switch from a
of a transition between the curved lead and the straight crossing
entry from the curved lead to the straight crossing
of superelevation over the turnout curve
(e) Gaps in
the gauge face and the running table at the crossing
in cross level caused by raised switch rails
In order to achieve higher speeds
on turnouts, it is necessary that all the limitations of the design of a
turnout be overcome as far as possible. In European countries, the design of
turnouts has been greatly improved and speeds of more than 100 km/ h are
permitted on turnout curves. The main features of the design of these turnouts
are the following.
curved switches are provided to avoid the abrupt change in the direction of the
vehicle at the entry to the switch.
and crossings are curved to the same radius as the lead curve or,
alternatively, a transition curve is provided between the toe of the switch and
the nose of the crossing. This provides a smooth passage to the trains on the
cant deficiency is permitted so that the disadvantage of not providing
superelevation on the turnout curve is duly compensated.
In keeping with the trend in the
railways of the world to permit higher speeds on turnouts, Indian Railways is
considering standardization of high-speed turnouts for the following conditions
of the track.
(a) For goods
yards for a maximum permissible speed of 25 km/h and for passenger yards for
maximum permissible speed of 50 km/h.
peripheries of big yards for bypass lines for a maximum permissible speed of 75
junction joints of single-line and double-line sections for a maximum
speed of 100 km/h.
A design of 1 in 12 turnouts for
passenger yards with thick web tongue rails and CMS crossings (RDSO Drg. no.
T-2733) has already been finalized for enabling a maximum permissible speed of
50 km/h. Similarly, a new design of 1 in 24 turn outs for BG routes with curved
switches and thick web tongue rails with a speed potential of 160 km/h is being
finalized by Indian Railways.