Roads:
1. If you have two or more different roads intersecting, in order to change priority you need to alter the priority setting in road template, not in a road spline. Road spline prio has effect only on roads that have the same template.
2. When setting up a road spline, use as much as possible terrain grid snap (best is to use 1/2 terrain grid snap). This way the road will look better because the spline points are aligned, and curves will look much more better. To do that, go to Snap toolbar on upper side of the editor.
3. On a road spline, from start to end, the second and second to last spline control points represents the start and respectively the end of your chose road texture.
4. If you plan to make a roundabout, is better to use a large static (I used an oilsilo which I sink it into the ground), then follow the chosen static contour to place your spline control points. the roundabout will look very professional

. Dont forget to delete the static you have used to guide you.
5.
Careful with "Apply spline" button !!! If the spline is not on the ground, when you hit apply spline, the ground will raise to meet the spline. If you want to lower/elevate the spline and not the ground, use
SNAP SPLINE instead(its not always available) If the snap button is not available and you know a control point is above the ground, grab a control point and drag it upwards, and you will see snap spline becomes available. When you hit that, ALL control points for that spline will snap to the ground.
Apply Spline button is very handy for creating ramps.
6. Static intersection. Its very recommended to use them(especially on tarmac roads), but take a look at point 3, above. Make sure the second and second to last spline's control points are overlapping the intersection. If it doesn't when you build the final road, the road will appear discontinued.