Some good science talk over on Reddit about this:
"First, is there any real difference on the carbon emissions between the car and the human riding a bicycle (quantity/quality/impact to environment etc.)? "
Without trying to be condescending... how is this even a question?
Assuming a male ride, bicycle rider + bike + gear is going to weigh around 200-250 pounds or so. A car + passenger + fuel, closer to 3,500 for a small car, 4,000 for a medium sized car. The amount of energy necessary to move a car the same distance as a bike is going to be an order of magnitude greater. No matter the carbon-based fuel source, there is quite simply no way for the car to be releasing less carbon back into the atmosphere than the bicycle rider.
To put this in perspective, it takes me 1 "hamburger" to travel 30 miles on my bike. That's about a gallon of gas for a car, or, according to this link
http://www.stewartmarion.com/carbon-footprint/html/carbon-footprint-car.html, 14 pounds of CO2. According to this link
http://micpohling.wordpress.com/2007/03/27/math-how-much-co2-is-emitted-by-human-on-earth-annually/, that's more than 10 times the total CO2 output of a human from a single day of breathing. Me upping my O2 intake for the hour it takes me to bike 30 miles is not making up the difference any time soon.
Making the argument that the total carbon footprint of a bike is worse than a car make no sense on any scale. Fuel costs are lower by an order of magnitude because energy needs are lower by an order of magnitude (and then some, as speeds increase). Production costs of the bike and the associated carbon footprint of manufacturing, lower by at least an order of magnitude (my bike: 28 pounds of metal and rubber) relative to the car.
Back of the envelope calc for total force applied to the road shows that a bicycle rider applies more force:
250 lb rider/bike with ~4in2 (1 inch x 1 inch x 2 tires) of contact = 62.5 psi 4000 lb car with ~144 in2 (6 inch x 6 inch x 4 tires) = 27.8 psi
I could see the congressman arguing that the increased force applied does more damage. I found one article talking about excessive truck weight having a larger impact than cars.
This is also kind of wonky. You are measuring the normal force, not actual applied sheering force to the surface of the road. You are in effect saying that the road is damaged by a stationary bike or a car. But it's not. A road is damaged by the force applied to the road by the tires of the bike or car from: acceleration, deceleration, and calculable rolling resistance. The latter will be about the same, in some senses. The value of first two? How many 30 foot burnouts do you see a cyclist doing from a stop light? How often do road bikes power slide during an emergency stop? How often does a road bike have to emergency stop from 60 mph? How about 40?
And that's the stuff that actually damages a road. Not just sitting on the road, but actual friction between the tires and the surface of the road during movement. Torque applied by the car's drive wheels is going to be much higher, rolling resistance is going to be much greater, heat generated much more significant, and the force applied from a sliding car much greater, all because the size and speed and momentum of the vehicle is commensurately higher.
The question you're asking here is superficially interesting but when you actually look into it, it's a bit absurd. The forces needed to move and stop a car are so beyond the performance profile of a bicycle.
DISCLAIMER Math done in links not verified by me, and could be wrong, in which case, I will revisit this post, but I don't have time to double check it.