Speed Limits

[shant]

Crap no wonder I'm burning so much gas driving to the valley and back at 80. [img]/images/graemlins/frown.gif[/img]

[jstnrgrs]

I actually think this would be a good idea for some highways that are hundreds of miles from a city.

Does anyone know why Montana abandoned their no limit highways?

[jason_t]

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Crap no wonder I'm burning so much gas driving to the valley and back at 80. [img]/images/graemlins/frown.gif[/img]

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80 + Santa Monica Mountains = bye-bye gas.

[DrSavage]

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2. fuel prices will increase---most automobiles have peak fuel efficiency between 55--65 mph and decrease in efficiency quite rapidly above that leading to more gas being consumed leading to an increase in prices. The rate at which we consume fuel will increase sharply possibly leading to


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That is because engines are being manufactured with speed limit in mind, if speed limit were to be raised I have no doubts we would have engines efficient at 65-70.

[James282]

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2. fuel prices will increase---most automobiles have peak fuel efficiency between 55--65 mph and decrease in efficiency quite rapidly above that leading to more gas being consumed leading to an increase in prices. The rate at which we consume fuel will increase sharply possibly leading to


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That is because engines are being manufactured with speed limit in mind, if speed limit were to be raised I have no doubts we would have engines efficient at 65-70.

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A lot of it is a wind resistance thing.
-James

[jason_t]

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2. fuel prices will increase---most automobiles have peak fuel efficiency between 55--65 mph and decrease in efficiency quite rapidly above that leading to more gas being consumed leading to an increase in prices. The rate at which we consume fuel will increase sharply possibly leading to


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That is because engines are being manufactured with speed limit in mind, if speed limit were to be raised I have no doubts we would have engines efficient at 65-70.

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I'm skeptical; do you have a reference?

[TheBlueMonster]

too many highways and (e.g. the DC beltway)aren't designed for higher speeds. You'd need to do some serious expansion of most roadways.

[zephed]

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2. fuel prices will increase---most automobiles have peak fuel efficiency between 55--65 mph and decrease in efficiency quite rapidly above that leading to more gas being consumed leading to an increase in prices. The rate at which we consume fuel will increase sharply possibly leading to


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That is because engines are being manufactured with speed limit in mind, if speed limit were to be raised I have no doubts we would have engines efficient at 65-70.

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A lot of it is a wind resistance thing.
-James

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.5mV^2, right?

[DrSavage]

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I'm skeptical; do you have a reference?

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Not really, but you can google some papers on internal combustion engine efficiency and see that it's mostly a function of RPM. From this I've concluded that if a car's transmission was manufactured with a gear ratio which would allow 75mph speed with engine running at 2500 rpm (which seems to be the optimum setting for whatever reason) it would be most efficient at that speed. James is correct about air resistance though, but since right now cars are often designed with some sacrifices to air resistance for general looks I believe this could be overcome as well.

[edtost]

my guess is that epa highway gas mileage is computed at ~55, so companies tune their cars to provide optimal mileage at that speed.

but i could be completely wrong.