In some years, when commuters take a ride in Chennai Metro Rail system from Koyambedu to St Thomas Mount, the train will snake through a zigzag path and maneouver some of the sharpest curves before reaching the destination.
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Not just this stretch, there are numerous sharp curves in the 116 km phase II project and it is one of the primary reasons why Chennai Metro Rail train will be operated at a slower average speed of 32 kmph when compared to the average speed of 34 kmph in phase I project.
According to officials of Chennai Metro Rail Limited (CMRL), there are sharp curves in various locations including Koyambedu, Manjambakkam, Porur, Alwarthirunagar, Alapakkam and Alandur. Across the phase II network, the sharp curves are present for almost 16 km (in different stretches) unlike phase I project where it exists only for a mere 4.9 km, an official said.
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“When the radius of the viaduct dips below 190 metres, the curve becomes quite sharp. While in Alandur the radius of the curve is as sharp as 125 metres, in Koyambedu it is 127 metres. The reason why we chose to go ahead with the existing alignment despite the sharp curves is to reduce land acquisition. For instance, during the planning stage, we knew that in the proposed alignment there is a sharp curve near Porur Junction and Alapakkam, we still decided to go ahead with the alignment. This is because, if we had to avoid the curve and change the alignment a little, it means we would have had to acquire more land,” he said.
But to ensure safety is not compromised and train doesn’t derail in these sharp curves, Chennai Metro Rail plans to fix ‘check rails’ near the tracks. “The ‘check rails’ are rails which we use when the radius drops below 190 metres. This apart, there will be adequate greasing of the train wheels too. These two measures help the train the negotiating the sharp curves. They will aid in reducing the screeching noises that commuters will hear when trains cross through sharp curves,” another official said.
Sources said, when the train operations begin in phase II network, if commuters should not have the inconvenience of screeching noises like it is occurring phase I network, there should also be regular maintenance of tracks apart from the measures that is being taken now.