Mid line between lane markings - Driving Path

I am required to develop a method that can identify the driving path (mid-lane markings) in 4 seperate images of roads.

I am using the hough function and houghlines function.

I am trying to plot the cyan line in the middle of the lane.

I understand the lines structured array has point 1, point 2, theta, and rho.

Can't quite figure how to relate it all together, i.e. using lines plot the mid-point between two lanes ( driving path) on 4 seperate images.