06
Sep 2006
by mark

Calculate Your True MPH

 “Let’s Race!”

I challenged Ehren to a three mile crosstown race. I would ride my bicycle (as fast as I could!), and Ehren would drive his Volvo, taking a normal route and traveling average speeds in his car.

The destination was slightly uphill from us.

 “Go!”

Soon the routes we chose to follow diverged, and I didn’t see Ehren until the destination.

He pulled in about 30 seconds after me, complaining about traffic.

On the trip we had both averaged about 18 miles an hour. I could tell this from the cyclometer that came with my bike. Ehren had no way to contest this– his Volvo didn’t have this feature.

Why would car companies neglect to provide access to such an interesting statistic, when bicycles can access it with a $10 device, just larger than an inch across?

I think I know why.

It’s depressing.

Without it, it’s easy to pay attention other numbers– how high the speedometer goes, or the maximum speed between stoplights.

Knowing that my crosstown speed in a car is less than twenty miles per hour, it makes me think differently about making the same trip on bike that, at a reasonable clip, might be 15 MPH.

Average Speed Calculation

The literal comparison above is just the tip of the iceberg. I decided to calculate the true average speed of a vehicle. I link to spreedsheets below.

The true calculation considers all the time that goes into the transportation. For a car, this includes time at the gas pump, getting oil changed, and washing the car. Most importantly, it includes all the time at I spend working to earn money just to pay for all of the car’s expenses.

Here are the ingredients for the calculation:

  1. The costs to operate the vehicle for one year. This may include car payments, gas, insurance, registration, accessories, maintenance– Everything. If the car is paid off, don’t forget to attribute some part of it’s cost to each year of it’s expected life span.

    It’s my understanding that about $300/month is a reasonably common figure here.

  2. Average hourly wage for the year.
  3. Total miles traveled during the year.
  4. Total time spent in the car for the year. You may want start with an estimate of what you spend on an average day, and then include some time for larger trips.

The spreadsheet then calculates:

  • The number of hours spent earning money just for the car
  • The total hours you spent on your car for the year (in it and on it!)
  • Average MPH for the year

The same formula could be applied to find the “true speed” of any transportation. My first volunteer to try the formula had spent almost as many hours earning money for her car as she estimated she had spent driving it last year– about 200 hours.

Her average driving speed was estimated to be about 19 MPH. I used the same formula to estimate the average speed of my bicycle: it came out to about 15 MPH…and a savings of over $2,000/year comparatively.

If some of that savings can be converted back into time, it can answer the question, “but what about the days I really need to get somewhere in a hurry?”

With a savings of $2,000 and a wage of $12/hour (after taxes!), that translates to an additional 3.2 hours per week, if extra time is chosen completely over saved money. The savings can actually free up more time for transportation, reducing the need to rush.

This formula illustrates when cars are most valuable to us: When traveling long distances. Given a long enough distance and an economical enough car, it would come out reasonably ahead.

Also keep in mind that this formula only deals with direct personal expenses. It does not factor in the health benefits that a mode of transportation provides, or systemic costs, such as the $34 billion dollars budgeted to be spent on federal highways in 2006. With about 293 million people, I estimate that costs each taxpayer about $150/year.

While it may seem far fetched to think about not having a federal highway system, it’s reasonable to consider that our government is able to adjust it’s priorities from subsidizing auto travel so thoroughly to putting more money into alternatives such as passenger rail travel, the most energy efficient form of mass transit.

I was surprised to find that improving passenger rail travel between cities is a Presidential Goal for 2006.

 “Let’s Race!”

Download the Spreadsheet to Calculate Your Own True MPH

Related Posts

If you thought that was interesting, you might also enjoy these related posts:

Tags: ,

  • Yogesh

    Can I calculate average speed of bike by engine specification?

  • Mark Stosberg

    Yogesh: No. Your average speed in a car has to do with how fast you drive it, not how fast it is designed to go.

  • Becca Fritschle

    We drove a Volvo XC for a while and it showed things like that. It was not encouraging. :(