I would agree with the several comments on the engineering and design of the higher speed roads being able to handle increased limits, but I don’t think the road or even most of the cars’ ability to go that fast are the problem. It’s the drivers. Raising the limits means people will go that much faster (the ones who are even bothering to stay close to it), and the risks will be higher and more deadly.
There is also the issue of fuel efficiency vs. speed and how little time is gained for a lot more gas used. Even with modern cars there’s a limit of aerodynamics and how much more it takes to push air out of the way faster as you get higher in speed. Of course this pales compared to how many people I see idling in parking lots on their phone, and then complain about gas prices. There’s a disconnect somewhere.
I tested my car as a hypermiler over thousands of miles on dead flat roads empty of other vehicles, my daily commute was 78miles. The most economical speed was 30mph in 5th gear with cruise control on. For most people that’s not a practical speed for any kind of long journey,but I was getting over 100miles per uk gallon in the summer (hot weather helps with fuel economy, as does not having headlights or ac on). I got through so many audiobooks driving so slowly!
Economy isn’t just about fuel economy.
Less unsprung weight and highly inflated tyres reduce fuel consumption, but low profile tyres result in damaged wheel rims and lack of adhesion results in lack of control.
Alloy wheels with low profile tyres are lighter, but are also more prone to irreparable damage.
If you have the smallest steel rims that fit over your brakes (and the highest profile tyres to match manufacturer recommendations), you are less likely to have a puncture or damaged wheel, especially in potholed regions. (I live in Victoria, Australia).
If you have the correct tyres inflated to the correct pressures, they will last longer and provide the most optimal grip.
That is not universally accurate. Even at the time, there were vehicles that were more efficient at higher speeds than 55mph. But those weren’t American designs, of course so they were of course ignored in favor of the general majority. And those vehicles that were more efficient at higher speeds, got screwed for simplicity.
Drag is not linear, it is proportional to the velocity squared.
However that is only one of the big factors. Vehicle shape and aerodynamics have a large effect on drag. This is one of the reasons for the flush door handles on some vehicles, lowered drag means increased efficiency. Then you also have the efficiency of the engine and power train at various speeds and power output.
I would agree with the several comments on the engineering and design of the higher speed roads being able to handle increased limits, but I don’t think the road or even most of the cars’ ability to go that fast are the problem. It’s the drivers. Raising the limits means people will go that much faster (the ones who are even bothering to stay close to it), and the risks will be higher and more deadly.
There is also the issue of fuel efficiency vs. speed and how little time is gained for a lot more gas used. Even with modern cars there’s a limit of aerodynamics and how much more it takes to push air out of the way faster as you get higher in speed. Of course this pales compared to how many people I see idling in parking lots on their phone, and then complain about gas prices. There’s a disconnect somewhere.
During the Arab Oil Embargo they lowered speed limits on highways to 50 mph, which is the most economical speed to drive.
Windows up is more efficient also, as is fully inflated tires.
I tested my car as a hypermiler over thousands of miles on dead flat roads empty of other vehicles, my daily commute was 78miles. The most economical speed was 30mph in 5th gear with cruise control on. For most people that’s not a practical speed for any kind of long journey,but I was getting over 100miles per uk gallon in the summer (hot weather helps with fuel economy, as does not having headlights or ac on). I got through so many audiobooks driving so slowly!
Economy isn’t just about fuel economy. Less unsprung weight and highly inflated tyres reduce fuel consumption, but low profile tyres result in damaged wheel rims and lack of adhesion results in lack of control.
Alloy wheels with low profile tyres are lighter, but are also more prone to irreparable damage.
If you have the smallest steel rims that fit over your brakes (and the highest profile tyres to match manufacturer recommendations), you are less likely to have a puncture or damaged wheel, especially in potholed regions. (I live in Victoria, Australia).
If you have the correct tyres inflated to the correct pressures, they will last longer and provide the most optimal grip.
That is not universally accurate. Even at the time, there were vehicles that were more efficient at higher speeds than 55mph. But those weren’t American designs, of course so they were of course ignored in favor of the general majority. And those vehicles that were more efficient at higher speeds, got screwed for simplicity.
I did wonder about that actually, questioned it.
It seems odd wind resistance would be higher at higher speeds and not linear to me as well. Idk why but it’s counterintuitive to me.
Drag is not linear, it is proportional to the velocity squared.
However that is only one of the big factors. Vehicle shape and aerodynamics have a large effect on drag. This is one of the reasons for the flush door handles on some vehicles, lowered drag means increased efficiency. Then you also have the efficiency of the engine and power train at various speeds and power output.