The CARB standards are per-mile. CARB standards for motorcycle total hydrocarbons + NOx are 800mg per km. For light-duty vehicles (cars and trucks and SUVs < 9000 pounds) the standard is 12 mg per mile (no, I do not know why one is in miles and the other is in km). So an SUV that holds maybe as many as 7 people emits much less.
Of all NOx emissions statewide from on-road cars and motorcycles, the motorcycles emit one third of it, despite being only 5% of the fleet and putting on < 1% of the fleet miles.
Of course motorcycles are usually a lot better on CO2.
It's also worth pointing out that motorcycles are surprisingly inefficient for their mass. If you're carpooling with 2 other people, chances are pretty good you're doing better than a motorcycle on CO2 and NOx both.
I would get something like 40? mpg city, maybe like 55 highway. Paradoxically, some of the best efficiency I had was at 90mph cruise, because I tucked behind the fairing, dramatically increasing my aerodynamics.
While I may be knocking on moto for co2/emissions, I feel compelled to note that motorcycles do not contribute substantially to traffic or road wear. If you see someone lanesplit past you in traffic, just be glad they're one less car in your way.
I've got nothing at all against motorcycles except for the idiots making noise.
If they're willing to take on the risk of riding around all these distracted idiots in SUVs, then more power to them.
I'd like to ride a motorbike but I just wouldn't feel safe considering how many close calls that weren't my fault that I've had in the car, despite considering myself a defensive driver.
