Speeding Ticket Math

Ajax von Kaiserpenguin via flickr

A few weeks ago I got a BIG speeding ticket.

Let me start by admitting that I like to drive fast, and I frequently drive over the speed limit. I don’t drive dangerously or recklessly, but I drive quickly. I have a long commute (don’t tell Mr. Money Mustache), and the fact that it’s been about 9 years since I’ve gotten a ticket (and much longer since I’ve been in an accident) suggests I’m not a menace on the roads.

It was a 45 mph work zone on a 65 mph highway. It has been a work zone there for almost a year now, and in that time I almost never seen any work going on. I now realize that this is because my usual commute takes me through the area before the workers show up. But on this day, I was going in to work later, and there were workers there.

And a cop.

I took my foot off the gas to coast down, and I was going 62 in the 45 when he got me. That ticket turns out to be $526. That’s a lot, and it taught be a very real lesson. I now drive 45 mph in that zone, regardless of the fact that there aren’t any workers when I normally go through it. But I’ve also been driving very close to the speed limit for my entire commute and I’ve seen something interesting: I get a lot better gas mileage.

I commute in a Honda Civic Hybrid. It gets great gas mileage, and it also gives me a lot of mileage information, including instant and average mileage. In my normal above-the-speed-limit driving style, I averaged 42.5 mpg consistently. But in my post-ticket cautious style driving, I’ve been getting around 50.3 mpg. Being an engineer, I tend to want to quantify things, so let’s do a little math here. I’ve been paying about $3.65/gallon for gas lately.

Cost-per-mile of driving fast:

(3.65 $/1 gallon)(1 gallon/42.5 miles) = $0.086/mile

Cost-per-mile of driving slow:

(3.65 $/1 gallon)(1 gallon/50.3 miles) = $0.073/mile

The difference:

$0.086/mile – $0.073/mile = $0.013/mile

So I save $0.013 per mile by driving slower. In round numbers, I commute about 20,000 miles a year, so that’s $260 savings per year in gas money. Or looked at another way, it will take me just over 2 years of driving slower to make up the cost of the ticket I got. Obviously, the best course is to always drive slower, and never get a ticket, and keep the $260 per year savings. I’m not here to preach about driving the speed limit. As I said, I enjoy driving fast (safely). And this story doesn’t wrap up with a nice tidy moral. I’m just interested to know the relative size of the numbers involved. It’s not thousands of dollars, but it’s not pocket change either. So, knowing this, I’m going to make a real effort to keep my speed down and my mileage up, for as long as I can stand it. And to avoid getting any more speeding tickets.

Here in the real world, I suspect that my speed will gradually creep up in the lonely rural parts of my drive, and stay low in the busy areas. I find driving slower adds about 5 minutes each way to my commute, which is already long. But a little reminder of how much my right foot can affect the contents of my wallet is worth keeping in mind.