Is there any way to change the size of the area blocked for civilians by pressing the "m" key?

I'm not really sure actually, I haven't looked for it. If you can, you would find it in the LCPDFR 1.0 manual + ini file. Take a look there :) 

Thanks for responding.

I've already done that but I didn't find anything there.
Furthermore, I have another question regarding the blocked areas:
Is it possible to deploy more than one area at the same time i.e. block both junctions of a street?

Changing the size is not possible. When using the Quick Action Menu you can deploy as many areas as you wish as long as you don't leave them. The "M" key however toggles the area.

Okay, thanks for the explanation! Maybe an area of adjustable size would be a cool feature for a future release, but thank you very much!