I noticed at my local In n Out burger that they have parking spaces next to the handicapped spots with signs reading "low emissions vehicle only" and I wanted to know if this is actually becoming common. Could you receive a ticket from a police officer for parking in these spots? I wonder what the threshold for emissions is for a vehicle to be considered low emissions. I'd expect the most that could happen is the store manager could have your vehicle towed if he really wanted but I doubt this would ever happen since it could open a floodgate of lawsuits.
You're not going to receive a ticket, they're relying on their customers to refrain from douchebaggery, same as those spots at grocery stores that are reserved for people with kids.
If your car is a LEV made in the last decade and a half it probably says it somewhere; I think mine has it on one of the windows. It's not just compact cars that are low-emissions vehicles, I'm pretty sure some trucks qualify (and I think the qualifications are based on the class of vehicle).
As in most cases where they rely on the population to not be douche bags, I doubt it works. I've never seen a spot reserved for LEV, but I've seen plenty of SUVs parked in spots reserved for compact cars - and those spots are smaller, so there is a legitimate reason to restrict them.