The most ambitious among them is the proposed Delhi-Varanasi-Siliguri corridor, which is expected to become India's longest high-speed rail line.
The four routes are part of the seven high-speed rail corridors announced by the Union government in the Budget and are expected to involve investments of nearly Rs 2 lakh crore.
Delhi-Lucknow-Varanasi corridor
The proposed Delhi-Lucknow-Varanasi bullet train is aimed at boosting connectivity across Uttar Pradesh by linking major religious, political and industrial centres.
The route is expected to pass through Noida, Jewar International Airport, Mathura, Agra, Firozabad, Etawah, Kannauj, Lucknow, Rae Bareli, Prayagraj, New Bhadohi and Varanasi.
A separate 124-135 km high-speed spur is also proposed to connect Lucknow and Ayodhya.
The corridor is expected to be 813-865 km long with 13 to 15 stations. Bullet trains will operate at speeds of up to 320 kmph, reducing travel time between Delhi and Lucknow to about 2 hours 10 minutes, and Delhi and Varanasi to around 3 hours 50 minutes.
The National High Speed Rail Corporation Limited (NHSRCL) has already floated tenders for civil structure design work.
Delhi-Varanasi-Siliguri corridor
The Delhi-Varanasi line is proposed to be extended to Siliguri, making it India's longest high-speed rail corridor and directly linking northern India with eastern India. There is also a proposal to extend the network further to Guwahati in Assam.
The proposed alignment includes Delhi, Noida, Mathura, Agra, Lucknow, Varanasi, Buxar, Patna, Begusarai, Khagaria, Katihar and New Jalpaiguri (Siliguri).
Stretching around 1,705 km, the corridor could slash travel time between Delhi and Siliguri from nearly 20 hours to about six hours.
The Railway Ministry is currently conducting surveys and feasibility studies for the project.
Delhi-Jaipur-Udaipur-Ahmedabad corridor
Another proposed high-speed corridor will connect Delhi, Rajasthan and Gujarat via Jaipur, Udaipur and Ahmedabad.
The line is expected to integrate with the under-construction Mumbai-Ahmedabad Bullet Train, enabling seamless high-speed travel between Delhi and Mumbai.
The proposed stations include Dwarka, Bijwasan, Gurugram, Manesar, Rewari, Behror (Neemrana), Shahpura, Jaipur, Kishangarh (Ajmer), Bijaynagar, Bhilwara, Chittorgarh, Udaipur, Dungarpur, Himmatnagar and Sabarmati (Ahmedabad).
The 886-km corridor will have 14-15 stations. While the Detailed Project Report (DPR) has been prepared, final financial approvals from the Centre and the concerned state governments are still pending.
Delhi-Amritsar-Jammu corridor
The proposed Delhi-Amritsar bullet train will pass through Rohtak, Jind, Kaithal, Chandigarh, Mohali, Ludhiana and Jalandhar before reaching Amritsar.
The route may later be extended to Pathankot, Jammu and Katra, providing high-speed connectivity to the Vaishno Devi pilgrimage.
The corridor is expected to span 450-500 km with 10-12 stations, reducing travel time between Delhi and Amritsar to around two hours.
The project is currently in the preliminary survey and route alignment stage.
Mumbai-Ahmedabad project to lead the way
India's first bullet train project between Mumbai and Ahmedabad is expected to begin operations on its Surat-Bilimora section in 2027, with the entire corridor targeted for completion by 2029.
In comparison, none of the four proposed Delhi-based bullet train corridors has entered the construction stage.
They remain at various phases of surveys, design, feasibility studies and approvals.
The government aims to build around 250 km of high-speed rail infrastructure every year and is also developing its first indigenous high-speed train, B35, whose trials are expected to begin soon.