I know that the third rail dual modes on all three railroads (MNRR, Amtrak, and LIRR) run off the third rail "where required" instead of "where available" like the ALP45s and future Amtrak catenary dual modes do and will. There are a number of disadvantages running on the third rail which is why they run only where required, but I was wondering, what's stopping the dual mode engines from using the third rail where available for HEP? I'm sure none of the current engines are wired to allow such, but would that even be a technical possibility that would have advantages? Mostly I'm thinking that the engine could put its full horsepower to the rail instead of having to use some for HEP which should also lower emissions and fuel use. But I admit, I know how much lower those would be.