Now that the paper plan is finished, I will begin the creation of the track using NURBS. This method involves extruding one curve along another curve to create two separate sections with no overlap, then creating a separate intersection piece to join the two sections in Maya. The blockers will be created entirely in Unity3D and their behaviours will be controlled their using custom scripts. The intersection controllers will be triggers that temporarily disable blockers of the same colour until two of them have been entered and exited.
Thanks to Rupert Morris for showing me the workflow to do this using NURBS, otherwise I would still be scratching my head wondering how to create curved roads in Maya that have simple enough UVs for me to work with.