Comments on: Speed Trials

By: mikey2gorgeous

mikey2gorgeous — Mon, 08 Jun 2009 12:20:59 +0000

@Nancy - The phrase “enough power to get you out of trouble” originated from motor cyclists limp excuses for buying big bikes (usually to wives, etc). In reality there is no emergency situation that warrants excessive speeding.

@ Lee - Sure, you can disable any system but with a large majority of people staying at the speed limit it would be easy to pick out offenders (or perhaps with hidden speed cameras). The penalty for driving a vehicle with a disabled system should be set quite high.

The swedish came up with a sat-nav that vibrates the accelerator when you exceed the limit. Quite neat as vibration like that is hard to ignore.

Interesting that in the UK one ‘pro-motoring’ group derides speed cameras because “you can’t concentrate on your speed & look at the road ahead” while another castigated plans for speed limiters as “taking responsibility away from the driver”. Truth is, it’s hard not to speed to some extent & drivers will come up with all sorts of bull to try and justify their speeding. We need government to step in & get speeding enforced properly by whatever means.

By: Lee Watkins

Lee Watkins — Thu, 04 Jun 2009 13:19:53 +0000

I was considering the effect speed limiters would have here in Baltimore, what with the frequent drive-by shootings, robberies, and rival gangs chasing each other - all in areas with posted 15-20MPH speed limits.

Perhaps only criminals will disable the system and speed.

A speed-limiting system that cannot be compromised would seem nearly impossible to implement. And if everyone is not limited, there would be cries that the system was unfair.

By: aaron

aaron — Wed, 03 Jun 2009 20:33:28 +0000

Here’s a neat paper: http://www.monash.edu.au/cemo/roadsafety/abstracts_and_papers/096/HawSym2.pdf

It suggests getting RPM up to 3000, but not higher, when accelerating. It also shows that traffic calming increases fuel consumption with questionable safety benefit.

But it does seem to indicate lower speeds are safer.

By: Nancy

Nancy — Wed, 03 Jun 2009 17:20:18 +0000

I’m glad to hear it, Aaron. I wish more drivers were like you.

By: aaron

aaron — Wed, 03 Jun 2009 16:54:46 +0000

That’s why I look first.

And I slow to a speed I can easily stop at for residential areas.

By: aaron

aaron — Wed, 03 Jun 2009 16:49:16 +0000

(it looks like I was wrong about 2100 being lowest fuel consumption. It looks more like 2500 for that engine– that’s for accelerating, not cruising)

By: Nancy

Nancy — Wed, 03 Jun 2009 16:45:12 +0000

Okay, so I’m wrong about the efficiency, but I don’t think it’s safe, especially when you might run into a red light runner. I am also more concerned about people other than just motorists being able to use roads.

By: aaron

aaron — Wed, 03 Jun 2009 16:33:56 +0000

Small amounts of power at low engine speeds actually consume more fuel than higher amounts of power and RPMs.

You may need to register to view the graph. Registration is free.

http://www.physicsforums.com/attachment.php?attachmentid=18980&d=1242755862

By: aaron

aaron — Wed, 03 Jun 2009 15:59:36 +0000

Actually it is, up ’til about 4000RPM (fuel consumption is lowest per power delivered at about 2100RPM, but it doesn’t increase significantly with additional power until much higher RPM). What’s inefficient is continuing to accelerate up to a stop. The drivers should be accelerating quickly, but laying off earlier.

By: Nancy

Nancy — Wed, 03 Jun 2009 15:06:41 +0000

The kind of behavior I see in the DC metro area is this: drivers speed to get to the next red light. Between lights, they put everyone else in danger, and they don’t ease congestion because they spend the same total amount of time on the road. Revving up quickly isn’t energy efficient.