Build a simple 2D square, placed on the ground. Extend along whatever axis you wish to drive the road. In photoshop, prepare a texture of the blacktop and divider. I suggest building in a square so its easier to anticipate the repeat. Apply in Bryce to your 2D with the setting of "parametric scaled". You may have to fiddle with it in the texture orientation editor, but it should give you the result you want. Failing that, there's a road in the Poser freestuff section, but you may have to convert it to a Bryce-friendly format.