CHENNAI: Driving past the intersections at Velachery, Pallavaram and Kolathur may be a new experience in a while as a steering committee on city infrastructure has approved new flyovers at these places.

A pair of unidirectional flyovers that cross each other at different heights will change the face of the Velachery junction. While Pallavaram will get the longest flyover in the city, at 1.3 km, Kolathur will have a much wider, six-lane, flyover.

Preliminary calculations show that these three flyovers would cost around 255 crore. "The cost could vary depending on the soil quality which decides the nature of construction," said a highways official.

The steering committee consisting of representatives from Chennai Corporation, Metropolitan Transport Corporation, Railways, Chennai Metropolitan Development Authority and Chennai City Traffic Police met on Tuesday to finalise a design for each of the intersections. The designs were done by Stup Consultants, a private firm. "The designs were chosen considering structural feasibility and land availability," the official said.

The Indian Roads Congress recommends construction of flyovers at junctions which have traffic of more than 10,000 passenger car units (PCUs). At the Velachery junction, where two arterial roads - Velachery Main Road and Velachery By-pass Road - meet, the traffic density is close to 10,500 PCUs during peak hours. The twin flyovers here have been proposed at a cost of about 82 crore. These will eliminate the need for signals.

At the junction where the two flyovers cross overhead, the first tier - meant for vehicles from the Guindy-Tambaram direction - will be at a height of 7 metres from the ground. The second tier, which will be at a height of 16 metres, will cater to vehicles going from Taramani to Velachery Bypass Road.

The project perhaps gives the biggest relief to ambulance services. "Once the new flyover is in place, the time taken for shifting patients from Velachery to the Government Royapettah Hospital will come down to 25 minutes," says B Prabhudoss, regional manager of 108 ambulance services.

The benefit could be the same for those taking GST Road from Tambaram to Guindy, once the proposed flyover comes up at Pallavaram. At 1.3km, it will be one of the longest flyovers in the city, and will run across three intersections where GST Road meets Kundrathur Road, Sandhai Road and Old Trunk Road. "I take at least 45 minutes to cross these three junctions. The proposed flyover will help me reach office on time," said James, a regular user of the stretch.

At the Kolathur intersection, where roads from Perambur and Red Hills join the Inner Ring Road, an 800 metre, six-lane flyover is being proposed to beat congestion caused by 13,000 passenger car units during peak hours. Engineers, however, warn that with increasing vehicular population, flyovers cannot be a solution forever. "This arrangement will cater to traffic only up to 2017," an engineer said.