MUMBAI, Oct. 26 -- Two key flyovers in south and central Mumbai -- the Sion bridge and the Sufi Saint Makhdoom Ali Mahimi flyover, popularly known as JJ flyover -- are set to undergo major maintenance work later this year. The bridges, vital links for daily commuters, will need to be partially or fully closed for about 15 days during the exercise. Officials from the Maharashtra State Road Development Corporation (MSRDC) said the work is "critical in nature" and involves replacement of the expansion joints, structural components that connect two bridge segments and allow safe movement due to temperature-related expansion and contraction. "In the case of Sion and JJ flyovers, we will seek night-time traffic blocks because of the heavy vehicular flow during the day," said an MSRDC engineer. "There are not many expansion joint plates to be replaced on JJ flyover though," the official added. An application for traffic permission is yet to be submitted to the Mumbai Traffic Police. "We will review the proposal once received and decide accordingly," said Anil Kumbhare, joint commissioner of police (traffic). However, officials pointed out that some of the initial work, such as dismantling the old expansion joints using specialised machinery, may have to be carried out during daytime hours, as the use of heavy, noisy equipment is not allowed at night. To minimise disruption, MSRDC plans to conduct these preparatory tasks early in the morning and temporarily place iron plates over the exposed joints to keep traffic moving. The plates will then be removed at night for continued maintenance work. Commuters, however, may experience traffic congestion at night during the block hours, particularly on routes connected to Mohammed Ali Road and the Sion junction. MSRDC is currently in the process of appointing contractors for both the Sion and JJ flyover projects....