After spending two and a half weeks in Hawaii, I’ve to appreciate driving slower. The first week was spent on the island of Kauai, an island that, to my knowledge, doesn’t have a road wider than two lanes on each side. The next four days was spent on the Big Island of Hawaii, which to my knowledge doesn’t have a road wider than three lanes. It wasn’t until reaching Oahu did we finally encounter what would be considered a highway (and it was a doozy, HI-1 is four lanes each way, sometimes more I think). On each of the other islands, I think I peaked at 55 MPH and that was only briefly. Part of the reason was because we were on vacation and took scenic routes – there’s no sense flying by at 70 MPH on a scenic drive; part of the reason was that you simply couldn’t drive 70 MPH on many of the winding roads. So that got me thinking, what do you really get out of driving 70 MPH? The answer is – **wasted gas and not much time savings**.

According to the US Census Bureau ^{[3]}, in 2006 the average time to commute from home to work ranges between 15 and 31 minutes. New York had the longest with 31 minutes and North Dakotans won with a mere 15.5 minute commute. The average was 25 miles.

The time you save between driving 55 MPH for the entire 25 miles, unlikely, and driving 75 MPH is seven minutes. It will take you about 27.3 minutes to travel 25 miles going at 55 MPH. At 75 MPH, you finish the trip in 20 minutes – a total savings of seven minutes. If you drive 65 MPH, you save only 4 minutes. So all that speeding, weaving, bobbing, and cutting off that you may do, in order to maintain that 75 MPH cruise, saves you a mere **seven minutes**. If the minimal time savings isn’t a deterrent (7 minutes out of 27 minutes is over 25%, so it’s relatively large), let us take into account some other factors.

## Speeding Ticket

In 2002, the average cost of a speeding ticket was $150 according to CNN Money ^{[4]}. Assuming inflation of 4% each year, the average cost can probably be extrapolated to be closer to $190. The time it takes for a ticket to be issued probably takes around 20 minutes, based on nothing but guesstimation. Let us assume that the probability you get a ticket is 0.1%, or one every three years, again also based on guesstimation. That means that the “cost” for speeding is 20 cents and 1.2 seconds each trip. The annual cost, if you assume 50 weeks of weekday travel, is $50 and five minutes. While not substantial, who wouldn’t want an additional $50 in their pocket? (This doesn’t take into account the cost of losing 20 minutes of billable working time, which would take into account your salary, so it’s a little more than $50 a year)

## Accidents

I won’t, because it’s too complex a problem that cannot be simplified enough to be of significant value, go into the financial and time cost of accidents the same way I did with speeding tickets. Suffice it to say, accident severity greatly increases when the speed of the vehicles is higher. I don’t know enough about traffic statistics to conclude that accident probability increases with speed but I wouldn’t be surprised if that was the case. Even if those could be quantified, I’m not going to try to research how much a life is worth, which is a pivotal calculation for insurance companies, so I’ll leave it up to the experts ^{[5]}. Either way, by driving fast, you are risking accidents and accidents cost time and money immediately and in over the long run (increased insurance costs).

## Gasoline Consumption

It is generally understood that driving the speed limit is the most fuel efficient speed. According to the US Department of Energy ^{[6]}, for each 5 MPH you drive over 55 MPH, you lose 6% of efficiency. That’s a whopping 24% if you drive 75 MPH, as in our earlier example. So, if your gasoline costs you $3.23 per gallon, you’re really paying closer to $4.00 per gallon. To drive this home, let’s compare the fuel cost of your trip to work with the 55 MPH speed versus the 75 MPH speed.

If your car gets you 30 MPG, a very generous assumption, then your 25 mile commute at 55 MPH will cost you 0.83 gallons of gasoline which is $2.69. In other words, it costs you $2.69 to drive to work. If you drove it at 75 MPH, your fuel efficiency drops such that the cost per effective “gallon” increases to $4. Now your trip costs $3.32, or 63 cents more. If you make this trip 250 times, that’s $157.50 extra each year on gasoline just for getting there 7 minutes sooner. (The math here is a little fuzzy in the sense that we’re just increasing the cost of the gasoline rather than keeping that constant and affecting the MPG, the reason for this is just to keep things easier. Ultimately the math isn’t ever going to be this clean so I think it’s a liberty that’s fair to take.)

## Summary

By taking into account just gasoline and the potential costs of a speeding ticket, we’ve seen that $200 a year can be cut out of your expenditures just by driving a little bit slower (that’s $200 based on $3.23/gal. for gasoline, it’s ever increasing!). So, if you’re feeling the pinch of fuel prices, consider something as simple as driving slower. If you’re concerned about those seven minutes, just leave home seven minutes earlier!