There are 1/4*40 = <<1/4*40=10>>10 more road signs at the second intersection than the first intersection.
This means there are 40+10 =<<40+10=50>>50 road signs at the second intersection.
The total number of road signs at the first and second intersection is 50+40 = <<50+40=90>>90
The third intersection has twice the number of road signs at the second intersection, meaning there are 2*50 = <<2*50=100>>100 road signs.
The total number of road signs at first to the third intersection is 90+100 = <<90+100=190>>190 road signs.
At the fourth intersection, the number is 20 fewer than at the third intersection, meaning there are 100-20 = <<100-20=80>>80 road signs.
All four road intersections have 190+80 = <<190+80=270>>270 road signs in total.
#### 270