Optimizing my commute
I'm looking for some help coming up with a formula that would help me optimize my commute. I realized the other day that I currently optimize my drive based upon some arbitrary combination of maximizing safety, minimizing likelihood of getting a ticket, and minimizing the duration of the trip. But that doesn't take into account that when one drives faster, the gas mileage goes down, and I'm now spending some $13 on my commute every day between gas and tolls.
Here's a description of my commute in words. Each one-way trip is approximately 69 miles. I usually drive around 74mph on the highway, and the total trip including traffic and local streets at both ends, and a few construction zones, takes on average 1:15. My gas mileage at 74mph on the highway is approximately 37mpg. Most cars achieve optimal gas mileage around 55mph, and the best I've ever gotten in my car was around 40mpg. I'm willing to assume a linear trend between (74mph, 37mpg) and (55mph, 40mpg). The gas station I usually frequent has a pretty consistent gas price of $2.56/gal. The interstate toll one-way is $1.50, and roughly 2 gals of gas per trip makes my daily commute cost roughly $13. If you're including a factor for the likelihood of getting a ticket, I find the most common speed of vehicles is around 70mph, there are cars going as slow as 60mph and as fast as probably 90mph, and I think I see one car pulled over per day on average, and less than one accident a week.
Clearly driving at the fastest speed possible will achieve me the fastest commute. (Though as it will probably also achieve me speeding tickets and losing control over my car, I prefer to keep it under 80mph.) Similarly, driving at 55mph will optimize my gas mileage. These are the trivial/limiting situations that you can use to put limits on your formula or check it.
But at what speed should I drive to get a good combination of gas mileage and time?
And a descriptive answer isn't *nearly* sexy enough - I can get off like that on my own. I want formulae at a minimum, and graphs if possible! :)
Here's a description of my commute in words. Each one-way trip is approximately 69 miles. I usually drive around 74mph on the highway, and the total trip including traffic and local streets at both ends, and a few construction zones, takes on average 1:15. My gas mileage at 74mph on the highway is approximately 37mpg. Most cars achieve optimal gas mileage around 55mph, and the best I've ever gotten in my car was around 40mpg. I'm willing to assume a linear trend between (74mph, 37mpg) and (55mph, 40mpg). The gas station I usually frequent has a pretty consistent gas price of $2.56/gal. The interstate toll one-way is $1.50, and roughly 2 gals of gas per trip makes my daily commute cost roughly $13. If you're including a factor for the likelihood of getting a ticket, I find the most common speed of vehicles is around 70mph, there are cars going as slow as 60mph and as fast as probably 90mph, and I think I see one car pulled over per day on average, and less than one accident a week.
Clearly driving at the fastest speed possible will achieve me the fastest commute. (Though as it will probably also achieve me speeding tickets and losing control over my car, I prefer to keep it under 80mph.) Similarly, driving at 55mph will optimize my gas mileage. These are the trivial/limiting situations that you can use to put limits on your formula or check it.
But at what speed should I drive to get a good combination of gas mileage and time?
And a descriptive answer isn't *nearly* sexy enough - I can get off like that on my own. I want formulae at a minimum, and graphs if possible! :)