I also had the same question but my observation was Madurai seem to get more residential areas in Natham road with people visiting Madurai core city daily for office/ school/ college just like how Tambaram, Guduvanchery developed as sub-urbs for Chennai city in late 90's. Apart from frequent townies, own vehicles etc, recent few years saw an increase in heavy vehicles taking Natham road to avoid Chittampatty toll. Hence, an elevated road would help in the long run for handle city traffic itself with minimal land acquisition. But priority of this road over other critical projects for Madurai is definitely debatable.Chennai and Trichy got good number of bridges and flyovers during previous tenures.
Now Coimbatore and Salem are seeing good development.
Only big city missing all the times in Madurai. I am not sure why they are building elevated highway on Madurai-Natham road. Whether this road has that much traffic? Instead they can build flyovers are Goripalayam, Keela vasal, Therku vasal etc which will ease the traffic to good extend.
This byepass steers left before entering Natham which would be more beneficial to vehicles towards Dindigul than to Trichy. Natham - Dindigul widening into 2 lane with paved shoulder and government medical college coming up in Natham road side of Dindigul, AIIMS coming up at Madurai are additional factors to make Madurai - Natham - Dindigul road busy compared to traffic along Madurai - Natham - Trichy. It is speculated that this road widening is picked up for TNPL players to reach cricket stadium at private college in outskirts of Natham (towards Dindigul) from Madurai airport. Will come to know the real traffic flow once all road projects around Natham are completed, specifically non-starter Natham Thuvarankurichi 4 laning.
Thanks & Regards