We need to lower the speed limit?

Question

Some of us can remember back to the mid 1970's when National speed limits were dropped from 70 mph to 55 mph on major highways. This was not a popular law, but it was necessary, and within several months we all became used to the slower pace. The speed reduction was mandated in response to an oil crisis which drove gasoline prices from about 30 cents to about 50 cents a gallon. Most citizens took it all in stride, while buying Datsuns, Toyotas, and Fiats which could get up to 40 mpg. So what have we learned in the last 35 years? We've learned that bigger is better, speed is a necessity, and d**n anyone who slows me down. It seems like we are in a pickle, very similar to the '70's. Truckers are slowing down, airlines can't afford to fuel up, people are whining about gas prices, there seems to be a fuel surcharge on everything, unrest in the Middle-East... Until technology can catch up to our demands (cross your fingers), we need to realize how important it is to conserve our finite oil reserves. One very effective way to do so is to drop our speed limits 10-15 mph on all highways. Besides the immediate affect of improved gas mileage, people can once again feel safe driving smaller, lighter cars. With the economy struggling, GM, Ford etc. could bounce back producing the small efficient cars which Americans are praying for. I'm sure 90% plus of those who read this will think that there is no way they will give up their 75mph fast lane. They will be the ones whining the loudest 5 years from now when gas is $5-6 per gallon.

Answer 1

The 55 mph speed limit sucked, didn't save much in the way of fuel and needlessly added time to long drives. I have an alternative (better) idea. Instead of slowing those of us down who have place to go I suggest we require all drivers who will not drive above 55 to be compeled to drive in the slow lane only or better yet require them to use surface streets and stay off the highways and freeways.   As for feeling safe in smaller cars that is such BS,  I've been in the Fire Service since I was 18 (am 47 now) and have seen more fatalities in the "economy" class cars than I've seen in real/normal (seating 5-6 adults) cars. BTW those wonderful little Hybrids are now becoming a big danger to emergency workers too.

Answer 2

As a matter of fact, I DO remember those days. I also remember that law being ignored by EVERYONE. It was only repealed because it encouraged scofflaws and made other laws harder to enforce. The law is a horrible tool for this kind of social engineering. The ONLY way to make people understand the stakes is with economics, and that does NOT include taxing to inflate the cost of fuel. People aren't stupid. If they think they're being fleeced you'll only get a backlash against the administration that gets caught with its hand in the cookie jar. When gas reaches $5-6 per gallon, people will start brewing their own ethanol at home. Revenoor.com sells stills for that purpose for only about $1500 or so. And when people can produce their own fuel, the oil companies will be worse off than anyone would ever have predicted.

Answer 3

The physics of fuel economy and drag is quite simple.  The number of gallons used per mile (gpm) is given by a simple formula;

gpm = idle / v + gpm_0 + a_laminar * v + a_turbulent * v * v,

where idle is the cost of simply running the engine, gpm_0 is the lowest gallons per mile (what's necessary to counter the friction in the engine and wheels), a_laminar is a constant when the air flow is laminar (smooth), and a_turbulent is a constant when the airflow is turbulent (high speed).  

For cars in the 70's the gpm_0 term was large (so the laminar term was ignorable), and turbulent airflow started occurring around 55 mph.  For modern cars, both the gpm_0 and laminar airflow terms are small, and turbulence starts around 70 to 75 mph.  Yes, traveling 55 mph instead of 70 mph might save a little fuel, but not much.  Going over 70 mph is almost definitely guzzling fuel, and people should pay attention to wind direction too.  Air resistance is based on the wind speed relative to your car, so a 20 mph head wind will cause turbulent flow at 50 mph, while a 20 mph tail wind will cause it at 90 mph.

The easiest way to tell if you're wasting fuel is by taking your foot off the accelerator.  If you slow by more than 5 mph in 2 seconds, then it's basically the same as riding your brake.

BTW, the WORST thing you can do for traffic, safety, and everyone's fuel consumption is to travel substantially slower than everyone else.  When you do this, you become a moving obstacle which forces people to merge.  This causes people to bunch up, which then causes them to slow down, and then bunch up more.  Eventually, it can even lead to a traffic jam.  In fact, this is how most traffic jams start on highways.  And that idle term blows up when everyone is going nowhere.

If you need to travel slow, then keep as far right as you can.  If you can't maintain the minimum speed (45 mph), then get off the highway (unless it's due to a traffic jam).  If you are approaching a congested area, then start slowing down a little, because creating better coordinated merges will ease the jam faster, and everyone can get going sooner.

Also, if you are aware that a jam awaits you... well... there's no need to rush up to it and then waste gas idling.  Give it some time to start clearing out.

Answer 4

I note your article mentions Datsuns Toyotas and Fiats.

GM, Ford, etc couldn't build a small, efficient, ergonomic car that could compete with Datsun, Toyota, and Fiat during the last energy crisis.

Nothing indicates that the American auto making industry can build small, efficient, ergonomic cars now either.

Oh yeah, gas is now $1.25 per liter in Canada. Equivalent to $5 per gallon US. The SUV drivers are still driving like a bat out of h**l. So much for the theory that higher prices will change behavior.

Answer 5

My old truck (that gets 30+ mpg at 55 and 22 or so at 75) cannot keep up with the speed of most traffic.   They still ignore the speed limit and go 90+ mph.   If I remember right, people might have gone 65 or 70 tops when the speed limit was 55.   Besides supporting terrorism less, thousands of lives would be saved by the masses going slower, something like 1000 extra people killed for each mph the speed limit is risen.   Most people won't accept this though; as the speed limit was risen, the auto industry has made vehicles able to go much faster.    Why does anyone need a vehicle that can go 120 or more with no problem?   I love that the truckers are going slower.   Its almost safe driving very early in the morning now.

Answer 6

I'm sorry but this is one of the worst ideas I have heard in a long time.  Lets clear one thing up right away.  Lower speed limits do not make people instantly safer.  When speed limits are set artificially low, tailgating, weaving and speed variance (the problem of some cars traveling significantly faster than others) and road rage make roads less safe.  Prior to the 1974 national 55 mph speed limit in the U.S., German Autobahns had a higher fatality rate than U.S. Interstates; however, a few years later, the Autobahn rate fell below that of 55 mph limited U.S. Interstates. IRTAD records show the U.S. rate remains higher than that on the largely unrestricted German Autobahn network.  

Besides, today's cars do not all get the best gas mileage when traveling at 55 mph.  This was the main reason that the speed limits were dropped during Nixon's presidency.  I can promise you that I get much better gas mileage in my vehicle when cruising along at 70 right with the rest of the traffic on the highway.  I have a six speed transmission and when I am forced to drive at 55 I am constantly shifting back and forth between 5th and 6th gear and that causes my car to use much more gas than if I were to travel along at 70 ducked in behind a tractor and trailer that is also running 70.

Answer 7

Driving fast is NOT a bad thing.  It allows more cars to use the highway at the same time.  It will reduce traffic and thus reduction traffic jam and it will in turn saves more gas.

The problem is NOT the speed, but the mileage driven.  People use more gas now because the average commute distance have gone up significantly!

Answer 8

The only thing the 55 mph law did was to make criminals out of honest men and women.  This wasn't the right move, it wasn't the right answer, and it's good Reagan got rid of it.

People have a need for larger cars.  Thanks to the CAFE standards, these cars could no longer be made, so auto makers gave the public even BIGGER cars on truck frames to do so.

Thanks to the CAFE standards fuel consumption rose.

If people buy bigger cars, if they drive fast, they pay for their actions.  Nothing needs to be done, as we can see that good intentions rarely provide the desired outcome.