The longest tunnel on the Delhi-Mumbai Expressway, passing through the Mukundra Hills Tiger Reserve (MHTR) in Rajasthan, is nearing completion.

This eight-lane tunnel, the first of its kind in India, features two parallel tubes with four lanes each, spanning a total length of 4.9 km. The tunnel includes a 3.3 km underground section and a 1.6 km cut-and-cover section. On 07 March, 2025, a breakthrough ceremony was held for Tube-1, connecting Kota to Chechat, marking the successful completion of its excavation

A senior National Highways Authority of India (NHAI) official stated, "While Tube-1 was fully excavated, 60 metre of excavation work remains in Tube-2 (Chechat to Kota), which is expected to be completed within a month. Following this, additional excavation will be carried out to increase the width and height in certain sections of the tunnel."

The excavation is targeted to conclude by June 2024, after which road construction and related works will begin. The tunnel will incorporate advanced systems such as lighting, sensors, pollution control, supervisory control and data acquisition (SCADA), and AI-based monitoring. Completion is targeted by December 2025.

The 1,350 km-long Delhi-Mumbai Expressway, which is designed to be upgraded to 12 lanes, has already seen 327 km of its 373 km stretch in Rajasthan opened to toll-paying traffic. However, full operational functionality will require the completion of interchanges.