Motorcycles only. The plan is to build two roller/retarder combinations, one just a variable load so that bikes can be static tested and the other a fully instrumented dynamometer.
If you build a twin roller setup (assuming the rolls are the same diameter) you can do brake testing as well... look at my "Mystery Project" and you may get the idea ...:-)
I'd seen that solution, but I've never found an electric motor that size for anywhere close to scrap prices. I could have added flywheels to my rollers to make an inertia dyno, but I really want a brake dyno for diagnostics.