New Delhi, June 14: Chennai could become India’s second city after Mumbai to have a monorail, opting for a cheaper and sleeker alternative side by side with the Metro that the Centre hopes will catch on as a trend.

Chennai’s plan for a 57km network of the elevated train service will need in-principle approval from the Centre. The Union urban development ministry has sent back a Rs 8,500-crore project proposal from the Jayalalithaa government seeking more details, an official said.

Mumbai’s monorail had a trial run on February 16 and is to become operational from August. Mumbai already has a Metro, and Chennai is building one.

At a time cities are scrambling for Metro railway projects, the Centre wants states to also look at the monorail. Among the monorail’s biggest advantages is that it can be built in congested areas and negotiate sharp curvatures, and needs less land.

A monorail train, which runs hugging a single concrete slab or beam narrower than the car and looks like a caterpillar climbing up a tree from a distance, however, carries just about one-fourth the passengers a Metro train can.

Another problem area is disaster evacuation, for which rescuers have to depend on the narrow skywalks that usually run parallel to the monorail track. Both monorail and Metro trains run at about the same speed.

It was Tamil Nadu’s former DMK government that had first proposed a monorail for Chennai in 2006. But the project was scrapped after a public interest litigation challenged the alleged irregularities in the tender seeking expressions of interest.

That project had envisaged a 300km network. Had that been carried out, it would have been the world’s biggest monorail project.

Jayalalithaa revived the project and floated tenders in August 2011 but the city transport corporation cancelled it because of lack of adequate participation. Now the project has been revived again.