I have travelled in both Sleeper and Semi Sleeper buses a lot of times. What I have observed is Sleeper buses are comfortable on four laned/ six laned smooth highways. In case of travel on smaller roads, two lane highways, roads with a lot of turns, ghat roads and roads with potholes, semi sleeper buses are a lot more comfortable.

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I have travelled a lot in sleeper buses a/c and non a/c both , it was very wonderful journey in sbc- bgm- sbc,
Sbc-mas-sbc,
But my first preference is one and only My favourite Trains 🚆😍😍.
Only disadvantages of buses is road traffic ( peak hours and market areas ) and dropping points in metro cities . Etc etc......

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One I've traveled to Baripada from Bhubaneswar by chakadola travels and it was a horrible experience (in 2005)
That was an only bus travel in night distance I've experienced since 2005.

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Sir, I had travelled a multiple number of times between Hyderabad-Chennai in Orange Travels AC Sleeper bus, and it was quite smooth and comfortable.

Recently during this February, I travelled from Chennai to Kumbakonam and vice versa in SETC Govt AC Sleeper bus. The journey was comfortable between Chennai and Vikravandi, due to the wide Grand Southern Trunk Road. But between Vikravandi & Kumbakonam, the roads had a lot of potholes, which made the journey somewhat uncomfortable.

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I am very prone to nausea, not only sleeper bus, but all the busses and even cars, I just puke 🤮🤮🤮.

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