Re-Institute National 55mph?

[homeworkhome53]

The scangauge is a tool, comparing better and worse, but I don't use scangauge readings for mpg recording. I only record miles driven divided buy fuel used at fill up after more than half the tank has been consumed. Just the way it's done in the fuel log here. I find the scangauge a ballpark figure, but love it as an improvement tool and to test mods and driving technique under simular circumstances. I think it teaches well.

homeworkhome53

[tjts1]

If everybody slowed down from 70mph to 65mph you would have 7% more cars on the road at any given time. Slow down another 10mph to 55mph and you increase congestion by 27%. WOW! This sounds like a great idea

What is so difficult about this concept? The slower you travel, the more time you are taking up space on the highway. Multiply that by thousands of vehicles you create congestion. The slower the flow of traffic, the more congested the road becomes. Everybody here is excited by the concept that "OMG I'm going to save by reducing my speed" Wonderful. But you can't see the bigger picture. Shame.

[MazdaMatt]

Good point, but it also reduced the required safe following distance and reaction time requirments to cancel that effect out. It also reduces speed differentials, which is a much better safety and "flow" benefit. Yes, it has increased cars on the road, but i'd say congention is relative to speed. a bunch of cars 15 feet away from each other is not congestion in a 30 zone, but a bunch of cars 15 feet away from each other IS congestion in a 70 zone.

Teach north america how to drive and value people's lives and the problem goes away!

[tjts1]

LOL nope, not true. People maintain the same following distance at 70mph and 55mph. It sounds great in theory but its simply not true.

[MazdaMatt]

Okay, true, but the benefit of what I was saying lies in safety. The whole highway is less likely to get plugged up by people smashing into eachother when 10' back doing 55 than 10' back doing 70.

[Lazarus]

Originally Posted by tjts1

If everybody slowed down from 70mph to 65mph you would have 7% more cars on the road at any given time. Slow down another 10mph to 55mph and you increase congestion by 27%. WOW! This sounds like a great idea

tjts1 you probably posted it before but do you have the study for that info?

[Bror Jace]

Repeating my request from a page or more ago, has anyone measured (gallons per hour OK) fuel consumption rates with a scangauge at 55mph vs 65mph? This kind of data is critical to this issue. I'd love to see factory-original cars as well as one or two with significant aero mods (as they are the shape of things to come).

The congestion idea is interesting, but not usually a factor in more rural areas where 65mph is currently the posted limit.

[Big Dave]

tjts is right. Reducing speed reduces throughput of a highway.

Aero drag is proportional to Cd. Reducing Cd will reduce fuel burn at 70, 55, or 35 MPH by the same proportion.

But if a lower speed limit is enforced in the name of fuel economy, people will despise the idea of fuel economy.

[Gregte]

Originally Posted by Big Dave

...But if a lower speed limit is enforced in the name of fuel economy, people will despise the idea of fuel economy.

Personally, I "despise" the fact that we have let our nation become so dependent on foreigners who generally dislike us!

Sometimes you gotta do what is best in the long run, not just what makes everyone happy.

[Bror Jace]

"Aero drag is proportional to Cd. Reducing Cd will reduce fuel burn at 70, 55, or 35 MPH by the same proportion."

I understand ... but there are, of course other factors involved such as gearing, weight, the way the engine is timed (any valve overlap in the name of higher peak power?) and the fuel mixture settings, etc ...

So, exactly how much would we save by speed limit alone? And aren't there better ways to save that (I'm guessing relatively small) amount of fuel?

Enforcement is another issue I'm not quite willing to concede. Sending hundreds of thousands of police officers out on the roads in immensely thirsty V8 pursuit vehicles chasing after Honda Civics driving 62mph makes little sense to me ... especially if the goal is saving fuel. We won't get 100% compliance ... so how much WILL we get? And at what cost? And is it all worth it?

Heck, if we could just get people to stay bellow 65mph we'd probably save a million barrels per day. What about excessive idling? That costs us another few million every day.

I started this thread hoping we could really compare and contrast the various ways we could save fuel nationally ... and hopefully, without limiting our freedom to travel just a bit more briskly on the open road.