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Comment by yequalsx | Hacker News Reader

People do know that it costs to drive a car but the cost is hidden in some sense. I think few people actually calculate how much driving really costs. When I drive 10 miles I don't think to myself that it's going to cost me $5.40 (using IRS mileage rate). Gasoline taxes do not come close to paying for the road system. I remember when gas hit around $5 a gallon in the U.S. some years ago people did think about driving cost a lot more.

I suspect if the costs were more apparent people would be more apt to support public transportation and reconsider their driving habits.

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When dreaming up new ways to tax cars, please bear in mind that wear on roadways from vehicles is proportional to miles driven times per-axle weight to the fourth power.

A gas tax is already proportional to miles driven times vehicle weight times a fuel efficiency factor.

Congestion, on the other hand, is a more difficult thing. Vehicle length certainly plays a factor, as well as width, acceleration, and braking distance. Number of passengers is an obvious factor. Trip routing efficiency has a role. I really don't expect local legislators to understand the mathematics of traffic. If they don't commission a study by traffic experts, and do exactly what those experts recommend, they might just end up making things worse.

https://en.wikipedia.org/wiki/Braess'_paradox#Traffic

https://en.wikipedia.org/wiki/Traffic_wave

Do you have a source for your roadway wear formula? Just interested to read more.

If you just google something like 'per-axle weight to the fourth power' you find lots of sources.

The AASHO Road Test is the ultimate source for the 4th power rule.

https://en.wikipedia.org/wiki/AASHO_Road_Test

You haven't added the external cost to society -- accidents, pollution, congestion and so on.

A study in Copenhagen found that the total cost (personal + to society) of cycling 1km was 8¢, versus 50¢ for driving, or 89¢ for driving at peak times. (That includes 16¢ given back to society in fuel tax.)

The low cycling figure is mostly due to the positive benefit to society of a healthier population (reduced healthcare costs, offset by slightly increased state pension costs when people live longer).

Unfortunately, the paper is a MS Word document: http://dx.doi.org/10.1016/j.ecolecon.2015.03.006 or https://www.researchgate.net/publication/274097090_Transport...

Accidents should be priced in via insurance; if the at-fault driver pays and liability insurance is mandatory, the costs are internalized.

The full reasoning for the accident cost is:

"Accident costs are founded in market values, and comprise public services (police, rescue and treatment), the loss of net productivity, premature deaths, minor and major injuries, and the cost of material damage. Costs are calculated in comparison to number of accidents related to cars/bicycles, and interpolated by the number of km driven/cycled. Accidents entail a cost of Euro 0.022/km for driving and Euro 0.106/km for cycling (COWI and Køpenhavns Kommune, 2009; Transportministeriet, 2010). Even though accidents involving cyclists entail lower material damage costs, overall costs are higher, as cyclists are more exposed and hence affected by accidents. As outlined by Transportministeriet (2013), there remains considerable uncertainty regarding average accident costs for cyclists."

I doubt the cost of treatment is recovered from road insurance policies in Denmark.

(Also NB this is urban driving at 50km/h, the accident cost of extra-urban driving may be higher.)

The marginal cost per mile is probably significantly lower (and will vary by vehicle) but I agree with your basic point. I expect that people would be a lot more inclined to combine errands etc. if they had to literally pay per mile.

Yeah marginal cost per mile is less. Perhaps that's why people rarely think about the cost of a 10 mile drive.

ghaff alluded to this, but there is also a disconnect between the cost at point of use and the sunk cost when it comes to cars. If you live somewhere where there are poor transit options, you must buy a car. Once you own a car, each additional mile is cheap, considering the conveience - gas taxes be damned.

It follows that converting a car-based city to a transit one necessarily takes away resources from the people who have sunk high costs into their acquisition of a car. That population almost always objects to transit-oriented development.

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