Links: Paying for gas and going the speed limit
Posted on July 25th, 2007 – 11:04 PMBy Roadguy
- Ka-ching at the pump: The Strib’s personal-finance blog looks at a poll on how consumers are dealing with higher gas prices; click here.
- Is slow the way to go? Pioneer Press columnist Joe Soucheray reflects on actually driving the speed limit.
- Service interrupted: A transformer fire brought light-rail trains to a halt in front of City Hall; click here.
25 Responses to "Links: Paying for gas and going the speed limit"
I spent a good chunk of time when I got my new car experimenting to figure out what the right speed was to get the best gas mileage out of my car. One of the main things I learned in that time is that you can’t tell who is going the same speed as you because, well, they’re going the same speed as you. You’ll never catch them and they’ll never catch you because you’re going the same speed. I also learned that a lot of people go the speed limit or thereabouts, especially in the Twin Cities. I usually go faster than the speed limit and have plenty of company, but I actually felt like I had MORE company when I was going the speed limit. So Mr. Soucheray’s article wasn’t incredibly interesting or enlightening. He just happened to be going the same speed as a lot of people, but he never caught up to them because he was going the same speed. How interesting does that make his article? … that’s what I thought.
And to comment further on his article, I’ve discovered that not passing on two lane highways is a Minnesota Tradition. I come from good ‘ole South Dakota where (God forbid) drivers are a bit more, shall we say … cavalier, and if they come up behind someone going the speed limit or just a bit over and happen to be going faster than that person they … well they do something foreign to Minnesotans … they pass them. Yes, I know it’s speeding, which is breaking the law, but it’s probably slightly safer than the Minnesota state tradition of tailgating people who drive the speed limit (or just over) because we’re afraid to pass them for fear of, well, breaking the law. Of course, Minnesotans happen to be very passive aggressive, so they like the whole tailgating angle much better than the passing one, that would be just too forward. But every now and then you get the renegade who decides to stick it to the man (and all the passive aggressive drivers) and pass a whole pack of Minnesota trained (and faithful) drivers at once.
The article was boring and pointless, but it sure did bring up a few of the things that bother me most about Minnesota drivers. Thanks Joe for the opportunity to vent.
Here’s what I posted under that speed limit article on the PP:
It’s a mixed bag IMO. Going the speed limit is the legal thing to do and you don’t have to worry (as much) about having to pass traffic, especially if you’re towing a boat or something.
But on the safety side of the issue, it’s safer to be going the prevailing speed of traffic, even if that prevailing speed is higher than the limit. It’s not speed itself that kills, it’s speed differential…one reason I oppose split car/truck speed limits that some states have.
I accept people who go the speed limit, even if I want to go faster. Where I get heated up is when people are going less than the speed limit and blocking traffic as such. 2-3 MPH less isn’t as big of a deal, but 8-10 MPH less is.
As for fuel economy, my car has minimal difference (less than 2 MPG) between 55 and 65. There’s more of a difference when I’m going above 70, but even then there’s only about a 4 MPG difference in my car between 55 and 75. And when I get over 30 MPG to begin with, that difference isn’t all that great.
BTW, Mike, I’m a Minnesotan and I have no compuncture against passing people on a 2-lane road, especially if they’re going under the limit, but even over (as long as I can keep it under 65, due to a quirk in state law).
Of course, many cars have inaccurate speedometers, so it’s hard to know if you’re actually going the speed limit or not. Most of the time, speedometers read higher than the speed you’re actually traveling (supposedly fulfilling some legal requirement across the pond). My car has a speedo which is wrong by 5-8%, but it reports a much more accurate speed via the OBD-II port under the dashboard, so I rely on a ScanGauge to set my speed most of the time.
Supposedly, cars from American manufacturers have the most accurate speedometers while European cars are worse and Asian cars are the worst. I’d like to see the MythBusters attack that someday, though I suspect they wouldn’t be systematic enough about testing it.
Anyway, the ScanGauge also attempts to calculate miles per gallon, so I can get a better idea of what I need to do to improve mileage, though traffic tends to be heavy enough in the Cities that I don’t worry about that in a lot of cases.
mulad….one point regarding manufacturers and speedometers. Several Asian manufacturers have facilities here in the U.S.
For example, I have a Toyota, but it was built in California. So regarding your middle comment is my car American or Asian?
That said, depending on the radar pinging me, my speedometer has either been spot-on or slightly fast…never more than 2 MPH.
I also think there’s some variation in radar, at least in the roadside “The Speed Limit is/You are going” stations. My speedometer on my Focus reads 4-5 mph fast according to Bloomington units, but only 1-2 mph fast according to Saint Paul units.
The other thing I want to comment on is Froggie’s mention of fuel efficiency. I have found that my car gets its best mileage at around 70-75 mph. It also doesn’t seem to have a marked drop off higher than that, though I don’t have much of a sample size of over 80. In any case, there is a far greater difference between stop-and-go mpg and steady mpg, regardless of speed. Based on that, I can’t help but think that addressing congestion is going to have a much larger impact than anything involving the speed limit.
The faster a vehicle goes, the more wind resistance is created which causes less miles per gallon of fuel used. If you have a vehicle like a corvette or a camaro you will have less wind resistance and can get better mileage than say a Jeep Grand Cherokee at higher speeds due to higher wind resistance and vehicle weight and more than likely a higher rear axle ratio. If you use cruise control and keep a constant speed you will use less fuel than someone that races up to vehicles in front of them and then hits their brakes. Easing up to the speed limit also uses less fuel than jack rabbit starts and stops. Having a lower rear axle ratio of say 3.23 compared to a higher ratio of say 4.11 will also allow higher speeds using the same amount or less of fuel. I hope this helps explain how you can get better mileage at higher speeds than other vehicles, but overall you will use less fuel with smaller vehicles and keeping a constant speed than you will with bigger SUV’s that weigh more, have bigger engines, higher rear axle ratios and higher wind resistance. Actually, the faster you go the greater the wind resistance increases exponentially.
Sorry Froggie, I don’t mean to insult Minnesotans, I was just venting about an annoyance I’ve noticed here versus there. You’re right, it’s the legal thing to do, so I probably shouldn’t pass someone who’s speeding already, but sometimes it does get under my skin.
And I’ve noticed my car will get around 35mpg at 55mph while it’ll get closer to 31 at 70-75. If I average above 75 it goes down significantly. There’s not a huge differece between 31 and 35 unless I’m going a really long distance, so that doesn’t bother me much.
And in relation to spedometer accuracy, try riding a motorcycle. My moto was always off by a margin of between 8 and 10% and nearly every other rider I talked to complained about the same thing, regardless of brand or country of manufacture.
DB -
You are leaving out a crucial factor in your fuel consumption calculation: gear ratios. Each gear has an optimal RPM range at which it is most efficient. Depending on what gear you need to be in at a given speed, and where that gear’s optimal range is, you may find some unexpected results. Of course, cars with CVTs don’t have this issue, as they don’t have gears. Even so, a manual transmission will be more efficient.
Also, while I agree that super fast acceleration will hurt efficiency, so will starting up too slow for the reasons mentioned above. You want to keep the engine at its optimal RPMs. Also, starting up too slow will not only cause you to burn more fuel than necessary, it will also leave more people idling at the stop light because fewer people could make it through before it changed.
And you have to balance efficiency with safety - If you’re getting on a freeway where the prevailing speed is 65 mph, you really ought to be going 65 (or close to it) by the time you merge, even if it isn’t as efficient as possible.
Regarding traffic driving the speed limit on two-lane roads, I have no qualms with them, just as I have no qualms with slower drivers on multi-lane roads(as long as they stay clear of the left lane(s)as much as possible).
I just pass when I get the opportunity. However, it would be nice if slower vehicles on busier two-lanes would turn out every now and then and let the pack built up behind pass.
Even better would be if more roads had passing lanes every ten miles or so as Hwy. 12 does west of the metro.
I’ve been in Mike’s shoes many times, and believe me, it’s noy just Minnesotans. It does drive me nuts too though: you see them coming up behind you a mile or more away in your mirrors (the shiny thing you have your garter, New Orleans beads and dreamcatcher illegally hanging from).
They continue to creep closer ’til they’re on your tail…..and they sit there. And sit there. I’ve slowed down to 45 mph before in an effort to get people off my a$$.
The mpg ’sweet spot’ obviously varies between each car. As noted in the comments here, basically you’re looking to get the engine operating at the optimum rpm for the car’s top gear, then subtracting the factors for wind resistance and friction.
I remember reading an article that tested a bunch of cars to try and find the sweet spot, and in their research, SUV’s (not surprisingly) had the slowest sweet spots, and small cars had the fastest. Still, they were all within a range of 45 mph to 65 mph.
In my personal experience, I can push 40 mpg in my car (mid sized sedan, 1.9 liter 4 cyl automatic) at 65, but it declines quickly if I go faster. It’s at about 33-34 at 70 mph and just below 30 at 75.
The problem with the MPG v. MPH argument is that it fails to account for gains in time becuase of less travel. I use to drive long distances on a very regular basis (think 500 mi plus in one day). If I could go 10-15 mph over the speed limit, I could often save myself 1 hour or more. Now, if that meant I had to buy an extra gallon of gas, it was $3 for an hour - a trade off I’m willing to make.
Same thing with the day to day commute. If I drive 10-15 over, I can save an hour per week. Will I take an hour in exchange for an extra couple of dollars in gas. Sure thing.
Prof S, do you also account for the other added increases by driving 10-15 over? Such as the price of the ticket (or tickets), the lost time sitting on the highway while pulled over, the increase in your insurance rates? How do those things figure into your cost-savings calculations?
1.) I haven’t had any speeding tickets (thankfully), but still think it makes sense overall.
2.) So long as you are not getting in accidents (I’ve never been in one), insurance rates do not increase. I do not think that driving faster when it is perfectly safe to do so (low traffic volumes, dry roads, etc.) increases insurance because there is no increase in loss.
3.) I’ll include those so long as we include the overall gains in productivity of every other driver getting to work faster because I am no longer contributing to the congestion.
– Each of these comments about increased insurance costs, increased risk of injury, etc. must be compared on a marginal basis. The marginal increase in cost (if any) for insurance is outweighed by marginal gains by spending less time in the commute.
Speeding tickets can affect your insurance rates. If it’s a moving violation, those are considered when assigning rates for insurance. (If it’s reduced to a equipment stop, for example, that’s no longer a moving violation.)
Whether it affects your rates somewhat depends on the insurance company and how often they check driving records of their clients. A single ticket may not change your rates, but multiple tickets definitely will. It also depends on how far apart the tickets are (2 tickets 10 years apart are going to have less of an effect than 2 in 2 years) and the severity of the offense (5 mph over vs 20 mph over).
I worked for an insurance company when I was in college, so I have first-hand knowledge of this.
Prof. S,
I think you misunderstand me. I have a great ‘feel’ for my car, and all of its rattles, noises, etc. From driving it, I’ve also picked up evidence on where the mpg sweet spot is. That doesn’t mean I drive to maximize efficiency all the time, but I have a better sense of how much my mileage declines as I go faster.
And, contrary to you assertions, I know plenty of people who have big trucks and SUVs that all used to drive like bats out of hell. When gas prices spiked after hurricane Katrina, they slowed down, and noticed significant savings in their fuel costs, at only a small decrease in time lost.
Admittedly, not all of this was based on cruising speed. A lot was reducing jackrabbit starts and stops, eliminating unnecessary accelerations, etc. Nevertheless, having that knowledge of how your car responds in various conditions is valuable information to have. That’s why I keep an eye on those things.
Also, according to actuarial statistics, speeding carries an assumed risk of loss. Statistically, speed is a factor in a majority of accidents, therefore insurance companies penalize you for speeding (assuming you are caught - i.e. recieve a ticket), regardless if you’ve never been in an accident. Same goes for other moving violations - like running a stop sign.
The same holds true for health issues, when it comes to actuarial stats. If you have a heart murmur, for example, you will pay a higher premium for additional medical and life insurance than “healthy” people do. That’s because - even if you are in perfect health otherwise - a heart murmur significantly increases your risk for other heart problems (like a heart attack). Therefore, you are a bigger risk to the insurance company. You may NEVER have heart problems, but the statistics say you are likely to and that’s what the insurance companies look at.
I believe in Washington State it’s the law that you have to pull over and let traffic past if there’s a certain number of cars behind you, I think it’s six, and there are signs to that effect, something like “unlawful to delay traffic, pull over when six or more vehicles are following”. The usual guideline I’ll follow is I’ll pull over if there’s more than three vehicles following me, or if a car’s been following 10 miles with no opportunity to pass. I was driving between Biwabik and Virginia when I pulled over to let a tailgater by. It made my day when 10 minutes later I passed him when he was pulled over by the cops.
A similar law exists in Virginia, though it’s not signed and I never saw it enforced.
And therein lies the problem with several traffic laws…there are too few police out on the street to enforce them.
Heather, the problem with your argument is that the insurance statistics are based off of people obviously driving too fast for what is safe. For example, someone approaches a corner too fast and drives off and hits a tree, or someone is speeding in the winter and spins out.
I’m talking about “safe” speeding, if you will. I’m talking about situations like this morning when there isn’t a car within 100 yds. of me and I’m driving 65-70 down I-94 (55 speed limit). Or, to put it in terms of the article, driving 65-70 on straight parts of cabin-feeder highways.
So long as you remain attentive to what is going on, there is nothing dangerous about driving over the speed limit.
It’s not “MY” argument - it’s a fact of how insurance companies determine premiums. Whether you are “safe speeding” or not, the fact remains (and the statistics show) that speed is a factor in most accidents - therefore, insurance companies usually will increase your rates if you are caught speeding.
You said in a previous post:
So long as you are not getting in accidents (I’ve never been in one), insurance rates do not increase. I do not think that driving faster when it is perfectly safe to do so (low traffic volumes, dry roads, etc.) increases insurance because there is no increase in loss.
I’m just telling you that you are dead wrong in this assumption. There is an assumed risk of loss - it doesn’t matter whether you yourself have been in an accident.
But you’re missing the point. The increased loss only comes if there actually is an accident. Then, the increase in loss is only present if the increase in speed actually affected the cost of that accident.
On the other hand, if you speed does not create a marginal increase in risk of accident (becuase you’re speeding in areas with little to no traffic), there is no increase in insurance rate.
Going over the speed limit does not necessarily increase the marginal risk of loss. Accordingly, speed alone cannot be said to increase premiums. Speeding when it is unsafe to do so (as I discussed above) would create such a marginal cost - and is what you are focusing on.
Whether I’m driving 55 or 70 on an open I-94 doesn’t lead to greater insurance rates because it doesn’t have a marginal increase in risk-costs.
On the other hand, if you speed does not create a marginal increase in risk of accident (becuase you’re speeding in areas with little to no traffic), there is no increase in insurance rate.
That’s not true. If you are caught speeding, your insurance company may increase your rates. (Depending on the situations I mentioned in a previous post, of course.) There’s no distiction on your speeding ticket that says “He was speeding in a safe location”. A speeding ticket is a speeding ticket.
Going over the speed limit does not necessarily increase the marginal risk of loss. While this is true, that’s now how insurance companies or actuaries see it.
The same principle applies to premiums for young men. Single men under the age of 25 pay more for insurance than women in the same age group. That’s because, statistically, men in that group are at the highest risk for loss to insurance companies. (They have more frequent accidents, or more expensive accidents.) That has absolutely NO reflection on how well (or poorly) a specific person drives, it’s just a fact of how insurance companies operate. My brother is one of the safest drivers I’ve ever known, but that didn’t change the fact that he paid more for car insurance than I did. Because he was unmarried, male and under 25, he was automatically charged more. That’s statistics and that’s the way insurance companies work.
Heather, your using the overall rule to apply to the individual. For example, according to your logic, “people generally earn more money as they get older, therefore you earn more money as you get older.”
It’s a logical fallacy. On the whole people who drive faster have greater losses. Undoubtedly. But, that does not mean that (a) speed causes the greater losses (i.e. it could be because the person speeds more, they are more likely to be careless), or (b) that my increase in speed creates a marginal increase in the loss.
The actuarial tables will also tell me that I’ll die at 72, but that doesn’t mean it’s true. My point is that, for many (if not all) of us, it’s cheaper to pay for the extra gas, drive faster, and spend less lost time on the roads.
Ben, My whole point was about gear ratios. The lower the rear end gear ratio is the lower your engine will be revving when in it’s highest transmission gear. My vehicle has a 4 speed automatic transmission and when it first goes into 4th gear that is when the engine is wasting the least fuel. The faster you go from that point on the more fuel you will waste and the more wind resistance you will have which wastes even more fuel. The best transmissions to have are standard trnsmissions because you can put them in neutral and coast up to red lights etc. while automatics start acting as a braking mechanism almost as soon as you let up on the accelerator. Any time you have to hit your brakes you are wasting fuel because you will have to use more fuel again to get back to the speed you had when you started braking at. It takes a lot less time and a lot less fuel to drive at a constant speed than to always be speeding up and slowing down by hitting your brakes. You are right about being at the speed limit when you are entering/merging onto the freeway, but if you have a lineup of vehicles behind you also merging onto the freeway, then everyone is going to have to be hitting their brakes to avoid hitting merging vehicles. Remember, the lower your engine is revving in all gears, but especially in it’s highest gear the least fuel you will be wasting and you will be helping to keep the cost of fuel from it’s constant never ending increases. But, I know there are some real important people out there that can’t be bothered with slowing down and not constantly racing on by everyone else and then hitting their brakes. Maybe they should get a helicopter or a private jet, God knows there isn’t any wasted fuel there and look at the time they would be able to save.
