This is a late answer and although it is marked as a duplicate I am posting an answer to clarify and use this as an example.
My design is going on a bus (12 m x 1.13 m) ... "resolution 1:1 scale 100 dpi" ...Does it means the resolution needs to be around 5000 dpi?
Designers need to use the correct units, values and operations. The 3 terms.
The correct unit is not dpi (dots per inch) this is a unit for printer resolution.
The correct unit is pixels per inch, ppi.
The operations (and values)
a) 12.00 x 1.13 m = 472.441 x 44.488 in.
b) pixel per inch is in fact a formula by itself. It is pixels/inch, px/in for short.
So: in x px/in = px.
When you multiply 472.441 inches x 100 ppi = 47,244 the result is plain pixels. That is the absolute measure of your image in pixels. 47,244 pixels width.
47,244 x 4,449 pixels.
A tip. Work at scale
As that is a big document for a raster program. Do that at a scale on a vector one, and at the end, export a raster image.
100 ppi is too much for a moving bus. 50ppi could be enough, that is a better file size.