This first one goes along with the advice given to ptclaus98 and his track
Here
From the single line drawing which settles from the think line into the "set" thinner line, select the Off-set tool and click inside the layout. (image 1)
From there off set half the width internally and then half the width externally to create a centre line with the outer and inner edges of the track (image 2)
Or make a single offset at the ful width of the circuit (image 3)