Upgrading Turnout and Loop Speeds to 30 Kmph

Up-gradation of Speeds on Turnouts and Loops to 30 Kmph

• Up-gradation of speeds on turnouts should cover a number of contiguous stations at a time to derive a perceptible advantage of the higher speed in train operation.
• Works described should cover all the running loops on the stretch of line taken up.
• Turnouts on the running loops should be laid with curved switches, with a minimum rail section of 52 kg/m.
• All rail joints on these turnouts should also be welded to the extent possible.
• Permissible speeds for different types of curved switches are:
  • 1 in 8½ curved switch: 15 Kmph
  • 1 in 8½ symmetrical split with curved switches: 30 Kmph
  • 1 in 12 curved switch: 30 Kmph (50 Kmph for TWS)
• The minimum track structure on the running loops should be 52 kg/m rails laid as Short Welded Panels, sleeper density 1540 Nos. per km, and 150 mm clean ballast cushion.
• Proper drainage of the area should also be ensured.

Turn-in Curves

• Turn-in curves should be laid with the same rail section as on the turnout with PSC sleepers.
• Sleeper spacing should be 65 cm centre to centre (maximum).
• Turn-in curve should conform to Para 408(2) and especially so in respect of curvature of the lead curve.
• Extra shoulder ballast of 150 mm should be provided on outside of the turn-in curve.

Indicators/Boards Provided in Curves

• Each approach of a curve should be provided with a curve board at the tangent point fixed on the outside of the curve.
• The board should indicate the radius of the curve, the length of the curve, length of transition in metres, and the maximum cant provided on the circular portion of curve in millimetres.
• Rail posts indicating tangent points should be erected on each approach of the curve, to indicate the positions of the beginning and end of transition curves.

Curves with Diamond Crossing

• Straight diamond crossings should not be provided in curves as these produce kinks in the curve and uniform curvature cannot be obtained.
• Where provision of such diamonds cannot be avoided, the approach curves of these diamonds should be laid without cant for a distance of at least 20 metres on either side of the diamond crossings.
• The cant should be uniformly run-out at the rate specified in Para 405 beyond 20 metres.

Extra Clearance on Curves

• On curves, additional lateral clearances, in excess of the fixed dimensions, should be provided as laid down in the Schedule of Dimensions.
• Clearances should be provided between adjacent tracks and between curved track and fixed structure.

Compensation for Curvature on Gradient

• Compensation for curvature should be given in all cases where the existing gradient when added to the curve compensation exceeds the ruling gradient.

Realignment of Curves

• The basic principles of string lining are as follows:
  • The chord length being identical, the sum total of the existing versines should be equal to the sum total of the proposed versines.
  • The slew in any direction at a station affects the versine values at the adjacent stations by half the amount in the opposite direction, when the track is not disturbed at the adjacent stations.
  • The second summation of versine difference between proposed versine and existing versine represents half the slew at any station.
  • At the first and at the last station, the slews should be zero.

This quiz covers the up-gradation of speeds on turnouts and loops to 30 km/h, including the length of section, works, and speed permits. It's essential for train operation and infrastructure management.