The planned Dhaka-Chittagong High Speed Rail Link will use dedicated 1435mm Standard Gauge Double line track with overhead catenary. It is expected to reduce travel time to 55~73 minutes between Dhaka and Chittagong while with current inter-city trains (1000mm gauge) around 6 hours of travel time are needed to cover the 321 km distance .
New route will be 227.3 km, approx. 90 km shorter using continuous welded rail, eased wide curves and minimal stops, maybe one or two. The project will be implemented under a government-to-government (G2G) agreement with China at an estimated cost of Tk. 50,000 crore. Part of the track is expected to run on elevated and sectioned off structure like the Japanese shinkansen.
Here is an OSM image for the planned route,
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Seems like the majority of high speed rail across the globe uses standard 1435mm gauge track.