The 4.89-km-long eight lane tunnel on Delhi-Mumbai expressway in Rajasthan’s Kota district is set to open by the end of July, said a senior official of National Highway Authority of India (NHAI) on Tuesday.The tunnel, which is part of a 8.3 km section and cuts through Mukundra Hills and tiger habitat, is one of the most critical link of the 1,386-km expressway project. With a width of 22 metres and a height of 11 metres, it is also one of the widest tunnels in the country, passing through different rock masses and substrata that include sandstone, shale, siltstone, mudstone and limestone.Apart from the tunnel section, another 26-km section from Sawai Madhopur to Laban in Rajasthan will open for traffic by the end of July.Officials said that with the opening of the tunnel, the entire Delhi, Rajasthan and Madhya Pradesh section of the project will become operational. Another 148-km stretch from MP-Gujarat border to Vadodara is scheduled to be operational by October, 2026. With this, a total of 912-km of 1386-km project will be operational by October 2026 from Delhi to Vadodara.The official further said that the tunnel is ready for the operation and currently few safety works are ongoing.The tunnel falls between Ummedpura and Nayagaon village in Kota and has been constructed as a joint venture between Dilip Buildcon Limited and Altis-Holding Corporation. It was originally a 30-month project scheduled to be completed in January 2024, but got delayed due to challenges during excavation like heavy water ingress and heavy rainfall. The tunnel even submerged in 2022, 2023 and 2024 and had to be redesigned considering the eco-sensitive nature of the region.The NHAI official said that the cost of the project was also revised from Rs 1,000 crore to Rs 1,250 crore.Story continues below this adThe 8.3 km project involves the construction of the highway, an open ramp, a covered tunnel and an underground or mountain tunnel. On both sides of the tunnel, there is a 480m and 1084m cut & cover, which is a camouflaged portion of the tunnel to allow animals to move from one side to another without any disturbance.Upon completion, Delhi-Mumbai expressway will become the country’s longest expressway built at a cost of over Rs. 1 lakh crore and is expected to cut down the travel time to 12 hours from the earlier 24 hours for the entire 1,386 km stretch.The first 246-km Delhi-Dausa-Lalsot stretch in Rajasthan was opened on February 12, 2023. This was followed by the opening of 100-km Laban-Gopalpura, 25-km Chechat-Jhalawar, 224-km Jhalwar-Ratlam-MP & Gujarat border and 67-km Bandikui-Jaipur sections. Dheeraj Mishra is a Principal Correspondent with the Business Bureau of The Indian Express. He plays a critical role in covering India's massive infrastructure sectors, providing in-depth reporting on the connectivity lifelines of the nation. Expertise & Focus Areas: Mishra’s journalism is focused on two of the country's most capital-intensive and public-facing ministries: Ministry of Railways: Tracking the operations, safety, and development of India's vast railway network. Ministry of Road Transport & Highways: Covering policy decisions, infrastructure projects, and highway development. What sets Mishra apart is his rigorous use of the Right to Information (RTI) Actas a primary tool for news gathering. By relying on official data and government records, he ensures a high degree of accuracy and trustworthiness in his reporting. This data-driven approach has resulted in numerous impactful reports that hold public institutions accountable and bring transparency to government operations. Find all stories by Dheeraj Mishra here ... Read MoreStay updated with the latest - Click here to follow us on InstagramTags:New Delhi