As I pointed out earlier this week, everyone that shops in Fort Collins pays to maintain our local roads (though it’s possible that bicyclists and transit users might pay a little more into the pot than motorists). But the flip side of that same coin leads one to ask: “Which road users make the greatest demands on those tax dollars?” Roads need to be maintained. But some vehicles cause more wear and tear than others, requiring additional maintenance.
There’s a measurement system used by street engineers called the “Equivalent Single Axle Load.” By estimating the types of vehicles that will be on the road, and their frequency of use, engineers can get a sense of how long the road surface will maintain integrity given a certain type of road surface (asphalt, cement, etc.). Heavy use areas may require more expensive, but longer lasting, surface materials, while light use areas will do fine with cheaper materials.
Speed also plays into the equation. In general, a vehicle traveling twice as fast will do twice as much damage to the road. If you think about driving behind someone on a gravel road, you’re more likely to have rocks kicked up into your windshield if they’re traveling quickly than if they’re moseying along at a gentle pace. That’s because they’re exerting more force with the wheels of their vehicle when they’re moving faster.
This example on W. Vine shows that the county saves money when repaving streets by only focusing on the part of the road damaged by heavy vehicles.
So how do various vehicles compare when it comes to chewing up the roads (and thereby costing us taxpayers more money every year)? Far and away the worst offenders are big rig trucks. The amount of damage they cause has led some to refer to the problem as the Hidden Trucking Industry Subsidy. Then there’s a range of cars that extends from the top end of the weight scale, such as the Hummer H2, down to the bottom end, such as a Smart Car. If we use the Generalized Fourth Power Law, which is a rule-of-thumb way to determine the level of damage caused by a particular load, then we can get some sense of how all of the different vehicles on the road compare in terms of how much damage they do to the surface of the street.
The American Association of State Highway and Transportation Officials (AASHTO) sets a 18,000 pound big-rig as the median vehicle size, and therefore it’s the scale against which all other vehicles are judged. (The largest vehicle allowed on the road has a maximum weight allowance of 80,000 lbs!) I picked a few random vehicles that we might see on our local roads and I’ve used the Fourth Power Law to determine how they stack up in terms of damage caused to roads.
| Vehicle | Approximate vehicle weight in pounds | Comparative level of damage |
| 9 ton big-rig | 18,000 | 1.000 |
| Hummer H2 | 8,600 | 0.0521 |
| Chevy Tahoe | 5,500 | 0.0087 |
| Toyota Highlander | 4,250 | 0.0031 |
| Average Car | 4,000 | 0.0024 |
| RAV 4 | 3,550 | 0.0015 |
| Prius | 3,050 | 0.0008 |
| Smart Car | 1,800 | 0.0001 |
| Fat Man on a Freakishly Heavy Bicycle | 350 | 0.0000001 |
Even a Hummer doesn’t come close to the level of damage that a big rig truck does to our streets and highways. But for the most part, big rigs don’t regularly travel through Fort Collins (except on state highways 287 and 14). So it makes more sense to look at an average car as the base level of damage caused to the roads. (According to the New York Times back in 2004, cars weigh 4,000 pounds on average.)
| Vehicle | Approximate vehicle weight in pounds | Comparative level of damage |
| 9 ton big-rig | 18,000 | 410.0625 |
| Hummer H2 | 8,600 | 21.3675 |
| Chevy Tahoe | 5,500 | 3.5745 |
| Toyota Highlander | 4,250 | 1.2744 |
| Average Car | 4,000 | 1.000 |
| RAV 4 | 3,550 | 0.6204 |
| Prius | 3,050 | 0.3380 |
| Smart Car | 1,800 | 0.0410 |
| Fat Man on a Freakishly Heavy Bicycle | 350 | 0.00006 |
It would take 410 average sized cars traveling on a road to equal the level of damage caused by one 18,000 pound big rig truck. But it only takes 21 average cars to cause the level of damage created by a single hummer.
Now let’s redo the chart from the perspective of a bicyclist. And rather than using a slim cyclist on a carbon fiber bike, let’s use the example of a large man on an old steel frame. This will give us a more conservative comparison of the levels of damage between bicyclists and other vehicle users.
| Vehicle | Approximate vehicle weight in pounds | Comparative level of damage |
| 9 ton big-rig | 18,000 | 6,995,485 |
| Hummer H2 | 8,600 | 364,520 |
| Chevy Tahoe | 5,500 | 60,979 |
| Toyota Highlander | 4,250 | 21,741 |
| Average Car | 4,000 | 17,059 |
| RAV 4 | 3,550 | 10,583 |
| Prius | 3,050 | 5,767 |
| Smart Car | 1,800 | 700 |
| Fat Man on a Freakishly Heavy Bicycle | 350 | 1 |
It would take 700 trips by bicycle to equal the damage caused by one Smart Car. It would take 17,059 trips by bike to equal the damage caused by an average car. And it would take 364,520 bike trips to equal the damage caused by just one Hummer H2. !!!!!
So let’s talk about this in terms of taxes. For the sake of argument, let’s say that every 1,000 miles traveled in an average sized car equals $1’s worth of damage to the road that will have to come out of City coffers for repair work. A bicyclist would have to travel over 17 million miles to cause the same $1’s worth of damage. Or another way to look at that, for the $1’s worth of damage that a car does to a road, a bicycle, traveling the same distance on the same road, would perpetrate $0.0005862 worth of damage. That’s about a tenth of a ha’penny.
In other words, every time you leave your car at home and take your bicycle out instead, you’re saving the City, and yourself, a car-load of money. It’s no wonder all new City streets are required to include space for bikes to share the road. The more people the City can get out of their cars and onto a bike, the more money can be spent by the City on other projects, like building a new community center on the southeast end of town.
So the next time you see a cyclist out on the street, be sure to give them a wave and thank them for all the money they’re saving taxpayers.
Spicy Garage from Ontario turned my chart into a graph and sent it in. This really helps visualize the difference between the vehicles.
Not to mention all the other benefits and being able to do almost anything your car can do.
Thank you Ms. Dunn, very useful!
Even in Singapore, where the cars are most expensive and motor related tax is amongst the highest, drivers are still being subsidised by non-drivers: http://lovecycling.net/2012/08/why-do-you-eat-my-road-cookie/
Actually, 18,000 lbs is the weight of just the tractor, without the trailer. In most states, 80,000 lbs is the maximum combined weight of a loaded tractor-trailer without getting a special hauling permit. Compared to trucks and weather, light trucks and smaller vehicles do negligible damage. The main costs they impose are pollution and congestion.
That’s a lot of weight. Thankfully, trucks that size don’t frequently travel most of our local city roads. We occasionally have a moving truck come in, or there might be utility equipment or road equipment, but otherwise it’s the light trucks and smaller vehicles doing the predominant amount of damage on our neighborhood roads. So when we’re looking specifically at taxes used to pay for local road maintenance, it makes sense to look primarily at the vehicles that are using those roads.
Trucks, for the most part, seem to stick to our local highways and interstate. But those are paid for through different taxes than our local roads.
You’d be surprised. Since pavement damage is a function of axle weight raised to the 4th power, garbage trucks are probably doing most of the damage to local streets. They can with as much as 64,000 lbs – equivalent to over 7000 SUVs.
So back to the topic. Where bikes really help is their low “passenger car equivalence” of 0.2. Five bicycles cause about as much congestion as one passenger car. This varies. The PCE is lowered by bike lanes and higher on narrow streets where bicyclists have to take the lane, and where heavy right turn vehicle traffic conflicts with through bicycle traffic.
At least almost everyone is equally culpable for the need to have a garbage truck come down the road. But when a motorist tells a bicyclist to get off the road because “they don’t pay taxes,” I think it’s important to point out that #1 Road maintenance comes out of sales tax, so everyone pays in no matter what kind of transportation they use. And bicyclists probably pay in more since motorists are more likely to travel out of town to go shopping than a bicyclist is. and #2 Though both types of transportation users are paying in to the system about equally, one is causing more damage to the roads than the other.
Granted, the garbage truck is causing the most damage of all. But if the motorist is going to complain about a bike on the road, they need to understand that that bicycle is costing the tax payer 1/17,000th of what the motorist is costing.
I think the cost of road space for bike travel is pretty much just the initial cost, and fixing it after time/the elements wear it out. For practical purposes, biking causes zero wear.
About those garbage trucks: isn’t Fort Collins especially bad about this? I’m not sure about the current situation, but I remember garbage districting was a failed proposal a few years ago, so that any particular residence still has the “freedom” to individually contract with any of three collection companies. Is this right? So much needless damage/pollution if so.
The problem of road damage just adds to the benefits of trying to not make so much trash.
Yes, instead of just having one ginormously heavy truck on our streets each week we have as many as people pay for service to within the neighborhood. So I know we have both Gallegos and WM in Old Town.
At least recycling is every other week. That cuts down on some road wear.
Oh, I forgot to respond to the “passenger car equivalence” measure that you mentioned. You’re exactly right. The real value of bicycle use comes from reduced congestion. But that only plays into tax dollars when it comes to re-engineering roadways to reduce the auto-congestion, which doesn’t fall under the road maintenance tax that I had written about in the first of this two part series. So when we’re talking about road maintenance, what does make sense to consider is who we’re maintaining these roads for — and that’s for the vehicles that are doing a whole lot more damage than a bike, whether we’re looking at a smart car, a Hummer, or a big rig.