To reach Dehradun from Sabroom, you must first travel to Agartala. From Agartala, you can take a train to Dehradun, usually involving a change in Delhi. The distance is over 2300 km. It is a long journey to the foothills of the Himalayas.
Total Distance: 2350 km by road, 1850 km air distance.
Check for connecting trains at Delhi station.
March to June and September to November for pleasant weather in Dehradun.