Huge trucking company cuts speed to 60mph

frankthetank

This is good. Top speed of 60mph.

bonehead

Excellent!Finally some signs of demand destruction.Let's hope it snowballs!
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Gimme some demand destruction.

joeltrout

Most trucks around here dont get over 50 mph anyhow due to traffic congestion. This will definitely help on the interstate highways though.

joeltrout
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JJ · Heavy Crude Joined: Aug 07, 2007 Posts: 294

H.E.Butt Grocery, for whom I work (320 stores) put governors on all our trucks.

Twilight · Expert Joined: Mar 02, 2007 Posts: 2971 Location: UK

Our trucks and coaches have had limiters fitted for years. The legal maximum is 60mph, but limiters cut that to 56mph.
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Armageddon

If you are driving slower, isn't it going to take you longer to get there ? I never understood how that saves gas. I understand if you are constantly flooring it, but if you are doing a constant speed of 65-70, how is doing 55 going to save gas ?

AirlinePilot

There is a trade off Armageddon. Slowing down causes slightly less drag, the engine works slightly less than at the higher speeds. With less drag and less fuel flow required you'll save fuel for a similar length and load trip. At some speeds the gear ratios will be best for fuel consumption also and will vary by truck type/load/ and terrain. It's a balancing act and at some point you are going to lose one way or another. For trucks there is probably a sweet spot around 50+/- 5-10mph I think. Faster and your fuel flow goes up due to drag and rpms required. Slower by too much and you'll still burn some minimum amount but it will take far too long to get there.

Same goes for aircraft and cars. I found that hypermiling in my older car the sweetspot was a certain rpm band that gave me about 45-50 mph in the higher gear(more efficient). If I got much slower I had to go down a gear and the rpms went up to hold speed. I'm sure the same is true for trucks and lots would depend on the route and the loads.

kjmclark · Heavy Crude Joined: Dec 09, 2005 Posts: 305

pup55 · Expert Joined: May 26, 2004 Posts: 3586

Fuel usage is greatly affected by aerodynamic drag, which varies non-linearly with speed. The higher the speed, the much higher drag per the above chart. The exact ratio of aerodynamic drag versus rolling resistance drag is related to vehicle shape, weight and speed.

By reducing the speed, you reduce the drag proportionately more, and it takes less energy to move the truck a given distance. You can also get savings by improving the aerodynamics of the truck (expensive, for all of those trucks) or reduce the weight (thus causing your shipping cost per pound of freight to go up).

It is true that by slowing the truck down, it takes more time to move the truck the same distance. If the cost of the time (the amount you have to pay the driver and lease the truck) is less than the cost it takes to move the truck (fuel) then it's a no brainer.

Note that there is a rolling resistance related component to this as well, which relates directly to the number and configuration of wheels on the truck. At some point, it becomes economical to use low-rolling-resistance tires (more expensive but usually wear out faster) versus normal tires (take a long time to wear out) if it saves a known amount of fuel.

These big truck fleets employ people whose job it is to track all of this information carefully, and they know exactly where the breakeven point is on all of these decisions.

So, it makes complete sense to make these guys drive more slowly.. It's the cheapest, most easily implementable way, as long as you are willing to sacrifice the time. There are also some safety and equipment wear issues that are affected by this that give added benefits.

It also makes complete sense to do it on passenger cars, which are subject to the same laws of physics. This was implemented in the US in the mid-70's with great success. However, doing such a thing today would involve getting everyday people to sacrifice, which is something that has been unheard of since roughly the mid 80's.

If you asked the motoring public, 'would you accept a 55 mph speed limit if it meant that we would not be sending as much money to the arabs, we would not have to send our kids to war in Iraq, it reduced the price of gas, and it made us less vulnerable to terrorism", they would say "hell no. It would take me an extra 10 minutes to get to work.

Sorry for the rant, but you might be able to save on the order of 5% of the national fuel usage overnight if you did this nationwide. The resultant .5 mbpd would probably be enough to cause some market slack, and the price to go down to some reasonable level.

Despite this, no one would reasonably suggest it.

Silly humans.

Goodyear

Cashmere · Light Sweet Crude Joined: Mar 27, 2008 Posts: 1477

One last thing. Every engine has an efficiency curve. Rev it too high, and you lose efficiency. Too low, same thing.

The tranny should ideally match the engine well.

The holy grail of transmissions is the continuously variable transmission, which would, ideally, allow the engine to spin at exactly the most efficient RPM for any vehicle speed.

As it is now, as you know, engine RPMS go from low to high, low to high, low to high as the tranny shifts (or you).

But the point is, one of my cars is revving very high at 65 (4000) while the other is not (3000), and the second gets 15% better fuel mileage at that speed for about the same size motor.

yesplease · Fission Joined: Oct 03, 2006 Posts: 2075

cube · Fusion Joined: Mar 12, 2005 Posts: 3352

You guys think we'll have a 55 mph national speed limit reintroduced to save fuel?

That's what happened with the last oil crisis. Or maybe everybody will just voluntarily start dropping their speed? Wink

Pretorian

yeah, you wish. i drive 60 where its 55mph and there is always someone beeping at me when i am on the left lane

perdition79

My company has our local trucks governed at 55 mph, and it's really not that bad. Our runs are about 35 miles each way, we do a few round trips a night between the port and the plants. We occasionally get to drive a 60 mph truck, and it only saves 5 to 10 minutes in the course of a 10-hour shift.

baha

My Dad just called from VA. He drove 1200 miles to get there. He has a new Altima with a CVT tranny. The EPA rating is 34 MPG. He drove the first tank of gas at 65 MPH and got 37 MPG with AC running. He was so impressed he drove the rest of the way at 60 MPH and got 42 MPG. This says to me that the new EPA ratings are based on 70 MPH on the highway and lots of passing with a heavy foot. If everyone drove 60 it could save as much as 20% over EPA ratings. That would seriously reduce demand and the price of gas. But as usual everyone wants to bitch about prices but no one wants to make any personal sacrifices to solve the problem. Why is it so hard to slow down and enjoy the scenery. Another benefit is that at 60 MPH you don't have to fight with the traffic, it just all zooms around you. Just stay out of the left lane!!
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