# Pounds that Kill: The Costs of Vehicle Weight

Eye-opening, if unsurprising stats on the consequences of ever-heavier vehicles on the roads:

Pounds that Kill: The External Costs of Vehicle Weight

Michael Anderson, Maximilian Auffhammer

Heavier vehicles are safer for their own occupants but more hazardous for the occupants of other vehicles. In this paper we estimate the increased probability of fatalities from being hit by a heavier vehicle in a collision. We show that, controlling for own-vehicle weight, being hit by a vehicle that is 1,000 pounds heavier results in a 47% increase in the baseline fatality probability. Estimation results further suggest that the fatality risk is even higher if the striking vehicle is a light truck (SUV, pickup truck, or minivan). We calculate that the value of the external risk generated by the gain in fleet weight since 1989 is approximately 27 cents per gallon of gasoline. We further calculate that the total fatality externality is roughly equivalent to a gas tax of \$1.08 per gallon. We consider two policy options for internalizing this external cost: a gas tax and an optimal weight varying mileage tax. Comparing these options, we find that the cost is similar for most vehicles.

1. Paul Kedrosky says:

As a dystopic colleague points out, imagine the healthcare savings, however.

2. Airbags weigh from 3-9 pounds each, depending on their location in the vehicle. On a car like the BMW 7-Series (which I believe has 10 bags) the total weight of all bags and associated sensors and wiring would be less than 80 pounds.

3. What many people forget is that heavier vehicles are safer for their occupants only when striking a "soft" target such as a lighter vehicle, house or convenience store. When striking an immovable "hard" target, such as a large tree or bridge abutment, extra mass is of no advantage. In this instance, 100% of the impact energy must be absorbed by deformation of the ramming vehicle, and this energy increases with vehicular mass in accordance with E=mc2.

• Andy says:

That's 1/2mv2 where m is the mass of the vehicle. mc2 is also happening where m is the mass of the car and tree electrons that are converted to energy.

4. Wonder if regulations on vehicle weight would be better than MPG/CAFE. (People buy huge cars to compete with the other huge cars in a crash.)