Why did doors become more flush with the body for modern buses

Silent · 21 Jul 2026

Just something I observed. I know with modern sliding plug doors this is logical but it happened on prior models that still used inward open/close doors.
I wonder if the less flush doors provided better insulation but insulation tech for the doors got better.

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GusB · 21 Jul 2026

Flush fitting doors will improve aerodynamics and potentially save fuel. Well, as much as the aerodynamics of a box on wheels can be improved!

61653 HTAFC · 21 Jul 2026

GusB said:
Flush fitting doors will improve aerodynamics and potentially save fuel. Well, as much as the aerodynamics of a box on wheels can be improved!

Probably a bigger impact on noise than fuel consumption.

Silent · 21 Jul 2026

I’ve read it’s easier to clean flush doors too, I think even it comes to machine washing. When I look at an electroliner, since noticing the doors more, it looks better sealed than the pointer2 showed in the image.

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61653 HTAFC said:
Probably a bigger impact on noise than fuel consumption.

How or why?

Leyland Bus · 21 Jul 2026

Silent said:
I’ve read it’s easier to clean flush doors too, I think even it comes to machine washing. When I look at an electroliner, since noticing the doors more it looks better sealed than the pointer2 showed in the image.

== Doublepost prevention - post automatically merged: 21 Jul 2026 ==

How or why?

Because the air will flow across the flat surface down the sides rather than being buffeted in the alcove of recessed doors.

In all honesty, the noise of that would have been minimal compared with the noise from the engine etc but every little helps.

Advancements in design technology probably helped aswell in bringing flush fit doors...

M60lad · 21 Jul 2026

Speaking of doors why (when fitted) are most dual door buses fitted with plug doors rather than inward folding ones like they used to be years ago?

AM9 · 21 Jul 2026

Leyland Bus said:
In all honesty, the noise of that would have been minimal compared with the noise from the engine etc but every little helps.

Probably, looking forward to the likely introduction of electric versions, where both the reduction of aerodynamic drag and the reduced noise that it brings would give a much more attractive product.

py_megapixel · 21 Jul 2026

M60lad said:
Speaking of doors why (when fitted) are most dual door buses fitted with plug doors rather than inward folding ones like they used to be years ago?

I believe one reason is that folding centre doors are at risk of hitting standing passengers. Of course this is not relevant for front doors as passengers don't stand next to them anyway.

Mark L · 21 Jul 2026

py_megapixel said:
I believe one reason is that folding centre doors are at risk of hitting standing passengers. Of course this is not relevant for front doors as passengers don't stand next to them anyway.

Indeed and that’s why the earlier New Routemasters, with the rear door that swings in, have an audible warning to stand clear of it.

61653 HTAFC · 21 Jul 2026

Silent said:
How or why?

Buses generally have a pretty high drag coefficient, being basically brick-shaped. Making the door flush with the bodyside will have a tiny, almost immeasurable impact on fuel efficiency (probably more significant for electric buses rather than diesel). However it'll reduce noise to a level that an observant passenger will notice- and drivers who are sat a few feet away from the door all day definitely will.

Mark L · 21 Jul 2026

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61653 HTAFC said:
Buses generally have a pretty high drag coefficient, being basically brick-shaped. Making the door flush with the bodyside will have a tiny, almost immeasurable impact on fuel efficiency (probably more significant for electric buses rather than diesel). However it'll reduce noise to a level that an observant passenger will notice- and drivers who are sat a few feet away from the door all day definitely will.

The average bus doesn’t really go fast enough to make aerodynamics much of an issue either!

Why did doors become more flush with the body for modern buses

Silent

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