Ever wanted to make a constant radius corner? There is a way...

[R Soul]

It's easy to make corners that look circular, but I've found that they are surprisingly far from being perfect. Fortunately there is a simple way of getting them right:

http://simtrackipedia.wikidot.com/crc

 

[tre]

You might want to add things like center lines and angle lines to your circle for extra helpfulness. Maybe something like this (10 deg. angles):

 

[martinez]

Great idea, thanks R Soul - I found by accident that somewhat also grid lines can be helpful to position the control points easily