Green Car Congress  
Go to GCC Discussions forum About GCC Contact  RSS Subscribe Twitter headlines

« Quantum Signs Alternative Fuel Systems Distribution Agreement for India | Main | American Lung Association Annual Report Shows PM Increasing in East, Ozone Down Nationwide »

Print this post

Ford Charts Fuel Savings Impact of Reduced Speeds

1 May 2007

Fuel consumption savings at different speeds. Click to enlarge.

Ford UK has provided performance data illustrating the effect of driving a cross-section of its Transit van models at governed speeds of 60 and 65 mph as a means to demonstrate the utility of a low-cost (£25) road speed limiter (RSL) it offers on its lineup.

On a Transit 260 or 280S 2.2-liter low-roof van, for example, driving 60 mph rather than 70 mph could save more than 19% on fuel consumption at cruising speeds—alongside a similar percentage cut in CO2 emissions.

CO2 reduction at different speeds. Click to enlarge.

By limiting speeds to 65 mph, a saving of more than 10% at cruising speeds is possible on the same model, again with a corresponding 10%-plus reduction in CO2 emissions. On a higher-powered Transit Jumbo, a cruising speed saving of almost 13% is achievable by governing top speed at 60 mph instead of 70 mph.

Across all the models, a 10 mph reduction (60 vs 70) roughly doubles the percentage fuel savings provided with a 5 mph reduction.

Many operators have been asking us about achievable ways of limiting their impact on the environment as well as reducing costs. For operations on which maximum motorway speed is not a critical factor, we believe use of RSLs to be one of the most cost-effective approaches.

—Kevin Griffin, Ford UK fleet operations director

The factory-fitted Ford Transit road speed limiter is an option on all diesel models.

May 1, 2007 in Fuel Efficiency | Permalink | Comments (27) | TrackBack (0)


TrackBack URL for this entry:

Listed below are links to weblogs that reference Ford Charts Fuel Savings Impact of Reduced Speeds:


A couple of graphs that relate vehicle drag factor and fuel comsuption would be nice. In other words, can we drive 70 in a vehicle with a drag factor of .22 and get better mileage that driving 60 in the same vehicle except a box front is added to increase the drag factor to that of a hummer?

Now I have nothing against lowering the speed limit for vehicles with drag factors over .3 to 45 MPH, because that would create an incentive to put cargo in slick vehicles and trains.

Interesting, but the transit has the aerodynamics of a brick. A speed limiter would be better if it allowed say 20 -30 seconds of higher speed (for overtaking), or if it rang an annoying bell (as they do in Japan) after 30 seconds to avoid people running out of speed while overtaking.
I wonder what the figures would be for a Focus or a Mondeo.
If you fitted a speed limiter, you might be able to use lower rolling resistance tyres as well.

As I recall, the info I've seen on this shows that driving right around 55 mph is the most optimum speed for fuel economy. On the other end of the scale, the very worst speed is zero mph while you are idling.

Microsoft says if PCs are not allowed to access uncertified websites there would be a 20% drop in virus infections. Meanwhile Apple is still virus efficient without such restrictions. Get my drift..

as one other poster commented, a limiter is a bad idea but something that nags is probably more effective. Although, if my parents are any example, I expect something that nags would be a trigger for road rage.

I expect one side effect a reduced speed to be people using cell phones more because they spend more time on the road, and they have more mental cycles free to multitask while driving. I also expect more close calls and accidents as people will get bored at the lower speed and spend more time paying attention to other things (scenery, radio, children, etc.) rather than at the road.

Isn't it a well known fact that pushing a heavy oversize brick over 55 mph requires more energy?

The solutions to reduce energy consumption are also well known but mostly overlooked by the big-3.

What is the real point here?

Is Ford's PR at work or just trying to get in the news?

In Auto Bild's testing every vehicle decreased in fuel economy above 50mph.

Come on now!!!! This is for frickin' commercial vehicles. This optional limiter is a TOOL for those with commercial fleets who may want to reduce their business costs (fuel).

By the way - 50 to 55mph is the best speed with MECHANICAL accessories. As the automobile's accessories and mechanically driven systems are electrified, I bet you will find the most efficient speed will begin dropping. My off-the-cuff guess would be a vehicle with electric p/s, electric a/c, and electric water pump probably is most efficient around 40-45mph.

This data, if made widely available to the general public would still be disregarded. They don't want to slow down to save fuel. They want the auto-makers to improve gas mileage so they can continue to go fast. Personally, I'd prefer both: Slow down to save gas AND have more fuel efficient vehicles.


The efficiency reduction over 55 mph has little to do with the amount of electric accessories put on the engine. Mostly, it is a matter of aerodynamic drag and inertia (I don’t know it well enough to explain it well). It takes more force to burrow a hole through the atmosphere at higher speeds, and the way the graph works, there is sort of a wall at around 55. Adding more electric draw on the engine changes the efficacy overall by a set wattage, but does not really change the physics involved with speed, and that wattage won’t change appreciably with the speed of the vehicle.

As for the rest of you, come on. Patrick’s right, Ford is not saying they don’t need better vehicles, Ford is saying that reducing speed is the quickest way to improve the fuel economy of a fleet of trucks, and they are right. Even your Prius can’t change the laws of physics, you will get better MPG driving around 55 MPH that you will at faster speeds.

Listen, we aren't talking about a Sunday drive to grandma's, time IS money. The cost of doing business is considerably less for fuel than for missing deadlines. That IS the only factor that matters. Improved gas mileage is the most important solutions. Drag coefficients could easily be brought down on the bricks by as much as 50%.

We have met the enemy and he is us.Behavioral changes could reap the fastest results.While many say they want to save the planet how many would choose to buy a governed car.If the public is going to demand advances toward sustainability from the pols are they willing to have some of the demand put on them.I sus pect a large number want to save the planet if the demands are of business and others.When the solution says you must do this and that many of the same people will balk.

The double nickle (55MPH limit) never worked in America. After a short time only served to enrich government coffers through prosecution and fines. It also promoted the sale of radar detection equipment to circumvent the Police, attempting to enforce the inane Law.

If you go 1 mph, or better yet zero mph, you will have no drag losses! So what else is new?


What I refer to is the reasoning why 50mph is more efficient than 40mph in a typical vehicle.

Your mechanical accessories are drawing a set amount of energy away from the engine to be driven whether at 5mph or 50mph (well actually, modern power steering is valved so you get MORE assistance at low speed and LESS at high speed so the energy used from the engine is less at higher speeds). Therefore, this "set" amount of gas being used to drive the accessories at 5mph is nearly the same at 50mph. Before aerodynamic drag requires a significant amount of energy (typically the modeling works as a linear relation to speed below around 50mph and a relation to the cube of the speed above 50mph) very little energy is required to continue at a steady state speed. Therefore, you get more distance out of nearly the same amount of gasoline usage whether at 50mph or 5mph.

Now enter electrical accessories...why will the peak efficiency be at a lower mph? Simply due to the LESSER energy demands to drive those accessories. If the accessories require less energy to be driven than the effects of aerodynamic drag will have a greater impact and accessory drag has a lower impact. Therefore the difference in fuel between 50mph and 5mph is much greater than with mechanical accessories.

Now, the more modern "intelligent" mechanical accessories might already be skewing the "peak" fuel efficiency speed down from the tested 50-55mph of the 70s and 80s.

As for time = money.

Unless you are travelling hundreds of miles each trip, 5 miles per hour makes very little difference in time.

65 mile trip at 65mph = 60minutes.
65 mile trip at 60mph = 65minutes.

5 minutes for a nearly 10% penalty in fuel efficiency on a vehicle that may be getting 15mpg when fully laden considering the nearly $6/gallon (US) fuel costs in the UK.

If they are really worried about time, they won't be telling their drivers to drive faster: they will install AVL/GPS devices. Typically, a driver can waste a few hours a day visiting his GF, stopping by a food place, going shopping, etc. I don't know if this happens in the UK but it DEFINITELY happens in the US and managers/business owners are clamoring for affordable GPS systems.

5 minutes? That is nothing.

2-3 hours of the driver slacking off? That is big money.

It depends on the transport. If automatic trans then its wherever the second overdrive gear kicks in. If manual then its whatever speed traddic mves so you can stay in cruising gear.

If people have to significantly alter their driving habits then green cars will never sell. If companies want these things to succeed then they need to work better than what they're replacing, not worse. I'm a speeder, put me in something that limits me for any reason other than safety, or beeps at me, and I'm not buying it. Build Hybrids. Make more aerodynamic vehicles. The End.

Elliot, you once again missed the point.

Let me make it clear for you:


If you are a "speeder" with a record you won't get a job working for me as a driver, end of discussion.

If I were to catch you speeding in my company vehicle, you would be reprimanded and fired upon repeat violations as it would be a company policy that you signed upon entering into an employment agreement with said company. NO ONE wants their company held liable for an accident...if the driver is speeding it makes it that much easier for a jury to rule against the company.

Why isn't the effect on traffic congestion mentioned?
Lower vehicle speeds can considerably deteriorate traffic flow. Last year an experiment was conducted in the Netherlands where the speed was limited from 120 kmh to 80 kmh in order to improve air quality and traffic jams around densely populated areas. The final outcome was that the traffic jams only increased by a factor 2 and subsequently the air quality got even worse.

I am not an expert on traffic flow, but one of the main reasons that where mentioned was that at 80 kmh people tend to drive a lot closer to the leading vehicle. This easily leads to traffic jams and accidents, which seems plausible to me.

The slower the speed, the longer you're on the road, too. At 80km/h, you're spending 1.5 times as much time on the road as you would at 120 km/h. The effect is you're forcing there to be 33% more cars on the road at any given time by reducing the speed limit by so much.

Lowering the speed limit is insane! I don't even see speed limits higher than 55 mph in my routine communte here in NY.

How about a Ford competitor to Toyota's Prius? That would save some fuel

Wow, people really want a technical work around to avoid physics.

Ryder truck rents trucks with 65 mph governors on them. Who, on this board, has opted not to rent a Ryder truck because of the governor? THAT’S what we’re talking about, not your car.

“For operations on which maximum motorway speed is not a critical factor, we believe use of RSLs to be one of the most cost-effective approaches.” It’s all there. For operations that don’t rely on speeding, not speeding is the most cost effective way of reducing emissions.

Prius' get far better millage if you stay under 65 mph, an it's a very aero dynamic car... infact, that is why the 2004+ models look like snoopy. The issue I have with driving 60 is most people in this world don't stay in the right lane and only use the left lane. Too many drives camp out in the left lanes just to drive 1 or 2 miles over the speed limit. That and too many people cut in lines, which is also aided by people leaving huge gaps in front of there cars... I just want computers to do the driving because most humans are idiots when it comes to driving.


Amen to that: Autonomous Vehicles. I hope the latest Darpa Grand Challenge is a huge success. Majority of accidents are caused by the idiots behind the wheel (bad choices, not paying attention, etc). The costs of vehicular accidents, every year, are over $200 billion ...more than $550 million per day. We spend less in Iraq (in an effort to keep our troops safe) then we spend to fix the damage caused by careless drivers.

I'm a commuter who drives 21mpd. I've changed my driving habits and have extended the time between fill-ups by several days. It's downhill to work, so I decided to see
if I could coast a considerable distance to my destination. It worked well. I realized that before my
little experiment I had had my foot on the accelerator
even during downhill driving. Now I coast over half the distance. Of course, I don't save anything on the uphill, but the overall savings are still considerable over a two week period. I pay the same amount at the pump every fill-up no matter how much upward the price climbs because my goal is to make it to a certain calendar day and I modify my driving in order to make it. I also drive a little slower, trying to start 5m
to 10m earlier on my drive to work. I realize that not everyone can be this disciplined; it won't work for everybody, but it helps my pocketbook, and for me, that's the bottom line.


With an attitude like yours I think you may have a hard time keeping any employees, let alone ones with clean driving records. And you can get over your fantasy of reprimanding or firing me, I wouldn't be remotely interested in working for someone like you in the first place.

That was my first post on this story, so I don't know how I could have missed the point "again." It was made in response to the story about Ford's governor, and had nothing to do with what you had to say. If you disagree with my broader viewpoint that alternative fuel vehicles (likely EV/PHEV) will never be truly successful until they're as fun to drive, capable, easy to refill and affordable as current cars, well, go ahead and disagree.

As for the story... it may be on commercial vehicles, but there are better things they could do, some of which have already been posted on. I don't want excessively lower speed governors spreading into consumer vehicles when I feel that instead Ford should be pursuing Hybrid technology.

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Your comment could not be posted. Error type:
Your comment has been posted. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.


Post a comment

Green Car Congress © 2013 BioAge Group, LLC. All Rights Reserved. | Home | BioAge Group