Is Every Speed Limit Too Low?

[jeffandnicole]

I've found that going 78 mph from NJ to FL doesn't phase the cops one bit, regardless of the speed limit (which is almost always going to be 65 or 70).

I'm also aware of the traffic around me.  If I'm doing 78 and passing everyone, then I'll slow it down.  If I'm doing 78 and in a line of traffic doing the same thing, I'll maintain my speed.  If I'm doing 78 and getting passed by people in the 80's, I'll speed it up.  Sure, I can't use the 'well, everyone else is doing it excuse' if I am caught, but the odds are with me that if a lot of traffic is going fast, I'm not going to stand out.   If the limit drops to 60 or 55, then I'll drop my speed below 70 or as appropriate for the conditions.

Overall, I've found traffic speeds to be increasing.  I see it most often in NJ, where I still believe 80+ on most of our interstates will get you stopped, but so much traffic is going 80+, the chances of getting caught are decreased (not to mention an absolute lack of cops sitting in the median lately...and those that do are usually visible from a long distance away).  But on my recent trip, unless there was a left lane hog in the way, speeds frequently exceeded 80 mph up and down the east coast. 

And that's even in Virginia, which actually has posted a sign in each direction on 95 saying that over 80 mph is considered Reckless Driving! (And really, that's hardly the definition of Reckless Driving...in most states, 11 over or 16 over the limit is called "Speeding".)  I only saw one sign each direction, both in the southern part of the state.  I would think a sign like this would be appropriate every few miles!

[inkyatari]

I remember when they widened I-55 between Weber Rd., and the I&M Canal (Southwest of Chicago,) from two lanes to three, in addition to doing a pretty crappy job of the whole project, they actually widened the shoulder on the other side of overpasses from the direction of travel to accommodate hiding police cars.

I keep wondering, if in three lane areas, if structuring each lane to a specific range of speeds would go.  45-65 right lane, 55-75 middle lane, 65-85 left lane. No semis in the far right lane.  Probably won't work, but I've been curious about this.

[texaskdog]

The only issues I have are at stoplights or when I get behind someone who is too slow.

Wait, is the limit the HIGHEST speed allowed or the lowest?

[jeffandnicole]

It should be noted it's the 85th percentile, not the 80th.

[The Nature Boy]

My biggest speed limit gripe is with I-91 being 45 MPH through Springfield, MA. No one follows it though and I can't see how it could even be enforced.

[kalvado]

It should be noted it's the 85th percentile, not the 80th.

Exact numbers are probably based on some assumptions about speed distribution. Which are, by their nature, just assumptions. Adding to the issue is 5 MPH granularity of speed limits - and speed distributions are probably not very wide, I can see data with average +/- 7-10 MPH
I suspect 80% to 85% difference is about 1-2 MPH, something like 77 and 79 respectively... And speed limit is going to be either 75 or 80 anyway.

[kalvado]

And I just like this image!

[kphoger]

Last time in 2013 one trooper was driving on there exactly 70mph with traffic as far back behind him as you could see, bumper to bumper, and getting visibly pissed with him. As soon as he turned off, it was like seeing the green flag at a NASCAR race. Everybody took off!

In the name of safety, no less!  I'd bet the farm there was a good share of reckless driving as soon as he turned off, with lots of people trying to get ahead of the pack and likely going even faster to do it than they would have in the first place.

[kalvado]

And as a personal note..
Lately my general highway speed went down by about 5 MPH. Reason? Upgrade to a car which has an MPG display. Although my old Civic still had better MPG than this one - just seeing how number changes with average speed is a good one for me.

[wxfree]

Regarding the 85^th percentile, what I read about it gave me the impression (although I may have been reading too much into it) that the real point wasn't the "85" number but was the shape of the speed distribution curve.  To describe, if the 85^th percentile speed was 73, there may be in a survey several cars going 71, several going 72, and several going 73, while maybe there are fewer going 74, only a couple going 75, maybe one or two going 76, another going 78, a few more in the 80s, and so on.  The 85^th percentile represents the highest speed with a cluster rather than a rarity of presumably reasonable drivers selecting that speed.  Those going faster have fewer other drivers choosing their speed, showing that they may be demonstrating reckless disregard for safety.  The point is that the 85^th percentile itself may not be a magic number, but just an average of where the shape of the distribution curve starts to change.  If the clusters change to isolated examples at a lower or higher speed, then that speed may warrant consideration as the limit.  Based on the way it was described, that's what I took from it.

I also listened to the discussion about the speed study conducted on I-20 in Parker County, Texas when the plan was to increase the speed limit to 70 only as far east as Weatherford.  The engineer said something about clustering of speeds and where that started to change as the reason for ending the increase at that point.  She talked about clustering rather than 85^th percentile numbers.

[jeffandnicole]

Regarding the 85^th percentile, what I read about it gave me the impression (although I may have been reading too much into it) that the real point wasn't the "85" number but was the shape of the speed distribution curve.  To describe, if the 85^th percentile speed was 73, there may be in a survey several cars going 71, several going 72, and several going 73, while maybe there are fewer going 74, only a couple going 75, maybe one or two going 76, another going 78, a few more in the 80s, and so on.  The 85^th percentile represents the highest speed with a cluster rather than a rarity of presumably reasonable drivers selecting that speed.  Those going faster have fewer other drivers choosing their speed, showing that they may be demonstrating reckless disregard for safety.  The point is that the 85^th percentile itself may not be a magic number, but just an average of where the shape of the distribution curve starts to change.  If the clusters change to isolated examples at a lower or higher speed, then that speed may warrant consideration as the limit.  Based on the way it was described, that's what I took from it.

85th percentile has nothing to do with clustering or a bell curve.

The NJDOT website does a good, simple job in explaining the 85th percentile. 

http://www.state.nj.us/transportation/refdata/roadway/speed.shtm

Average speed or mean speed is the sum of all individual speed measurements divided by the total number of vehicles.

Median speed - the speed at or below 50 percent of vehicles travel.

85th percentile speed - the speeds at or below 85% of all vehicles are observed to travel under free flowing conditions.

[kalvado]

Agreed. Just as setting the speed limit too low so that most people speed doesn't change the equation either. I'm not arguing for keeping people with licenses who have lost their ability to drive. I'm pro increasing enforcement of other laws like keeping right except to pass, tailgating, and use of turn signals in place of all speed enforcement.

I would take a once every 5 years trip to court due stupid speed limit rather than daily clusterfuck on the road due to thoughtless "keep right" enforcement

[bzakharin]

From what I've gathered, speed limits were generally adhered to until the NMSL made every highway 55, regardless of how congested or sparse traffic was.  After that point, speed limits became a political pawn for all roadways rather than a useful engineering instrument.

That doesn't explain why people go +9 or more on roads where the speed limit is well below 55, such as 25 on residential streets which, as far as I know did not change significantly during or after the NMSL.

[Brandon]

From what I've gathered, speed limits were generally adhered to until the NMSL made every highway 55, regardless of how congested or sparse traffic was.  After that point, speed limits became a political pawn for all roadways rather than a useful engineering instrument.

That doesn't explain why people go +9 or more on roads where the speed limit is well below 55, such as 25 on residential streets which, as far as I know did not change significantly during or after the NMSL.

The NMSL taught drivers that speed limits, any speed limit at all, just don't matter.  It was a major mistake that will take a few generations to fix.

[vdeane]

Agreed. Just as setting the speed limit too low so that most people speed doesn't change the equation either. I'm not arguing for keeping people with licenses who have lost their ability to drive. I'm pro increasing enforcement of other laws like keeping right except to pass, tailgating, and use of turn signals in place of all speed enforcement.

I would take a once every 5 years trip to court due stupid speed limit rather than daily clusterfuck on the road due to thoughtless "keep right" enforcement

"Keep right" is a major reason why Germany can have roads without speed limits and we can't.

[kalvado]

Agreed. Just as setting the speed limit too low so that most people speed doesn't change the equation either. I'm not arguing for keeping people with licenses who have lost their ability to drive. I'm pro increasing enforcement of other laws like keeping right except to pass, tailgating, and use of turn signals in place of all speed enforcement.

I would take a once every 5 years trip to court due stupid speed limit rather than daily clusterfuck on the road due to thoughtless "keep right" enforcement

"Keep right" is a major reason why Germany can have roads without speed limits and we can't.

I didn't have a chance to drive in Germany yet.. But maybe 0.03 alcohol limit also plays a role? Maybe 80% manual transmissions? Maybe more relying on common sense and less on US-style legislating proper sneezing procedures?
Putting it simple - every single day I see 2-3 idiots insisting on keeping right near exit 7 northbound on Northway. You want to enforce that idiocy?

[kphoger]

Agreed. Just as setting the speed limit too low so that most people speed doesn't change the equation either. I'm not arguing for keeping people with licenses who have lost their ability to drive. I'm pro increasing enforcement of other laws like keeping right except to pass, tailgating, and use of turn signals in place of all speed enforcement.

I would take a once every 5 years trip to court due stupid speed limit rather than daily clusterfuck on the road due to thoughtless "keep right" enforcement

"Keep right" is a major reason why Germany can have roads without speed limits and we can't.

Agreed.  Decently high traffic volumes, generally no more than two or three lanes each direction, top-of-the-line luxury sports cars sharing the road with motor homes, trucks limited to low speeds...  Without people keeping right (or at least moving right when being approached), there would be more accidents.

Maybe 80% manual transmissions?

I don't follow.  How does having a stick shift help prevent accidents?

[PHLBOS]

Maybe 80% manual transmissions?

I don't follow.  How does having a stick shift help prevent accidents?

It keeps one focused on driving and not doing other things that are considered distracted driving.

[kalvado]

Agreed. Just as setting the speed limit too low so that most people speed doesn't change the equation either. I'm not arguing for keeping people with licenses who have lost their ability to drive. I'm pro increasing enforcement of other laws like keeping right except to pass, tailgating, and use of turn signals in place of all speed enforcement.

I would take a once every 5 years trip to court due stupid speed limit rather than daily clusterfuck on the road due to thoughtless "keep right" enforcement

"Keep right" is a major reason why Germany can have roads without speed limits and we can't.

Agreed.  Decently high traffic volumes, generally no more than two or three lanes each direction, top-of-the-line luxury sports cars sharing the road with motor homes, trucks limited to low speeds...  Without people keeping right (or at least moving right when being approached), there would be more accidents.

How all that relates to "no speed limit"?

[kphoger]

Agreed. Just as setting the speed limit too low so that most people speed doesn't change the equation either. I'm not arguing for keeping people with licenses who have lost their ability to drive. I'm pro increasing enforcement of other laws like keeping right except to pass, tailgating, and use of turn signals in place of all speed enforcement.

I would take a once every 5 years trip to court due stupid speed limit rather than daily clusterfuck on the road due to thoughtless "keep right" enforcement

"Keep right" is a major reason why Germany can have roads without speed limits and we can't.

Agreed.  Decently high traffic volumes, generally no more than two or three lanes each direction, top-of-the-line luxury sports cars sharing the road with motor homes, trucks limited to low speeds...  Without people keeping right (or at least moving right when being approached), there would be more accidents.

How all that relates to "no speed limit"?

It relates because in Germany there is a very wide range of speeds encountered on the highway.  With more restrictive speed limits, the range of speeds encountered is narrower, and therefore the frequency of lane use conflict also decreases.  Or, to put it another way, a guy legally driving 100 mph is going to encounter fewer obstacles if the left lane is kept clear than if it isn't.

[kalvado]

Agreed. Just as setting the speed limit too low so that most people speed doesn't change the equation either. I'm not arguing for keeping people with licenses who have lost their ability to drive. I'm pro increasing enforcement of other laws like keeping right except to pass, tailgating, and use of turn signals in place of all speed enforcement.

I would take a once every 5 years trip to court due stupid speed limit rather than daily clusterfuck on the road due to thoughtless "keep right" enforcement

"Keep right" is a major reason why Germany can have roads without speed limits and we can't.

Agreed.  Decently high traffic volumes, generally no more than two or three lanes each direction, top-of-the-line luxury sports cars sharing the road with motor homes, trucks limited to low speeds...  Without people keeping right (or at least moving right when being approached), there would be more accidents.

How all that relates to "no speed limit"?

It relates because in Germany there is a very wide range of speeds encountered on the highway.  With more restrictive speed limits, the range of speeds encountered is narrower, and therefore the frequency of lane use conflict also decreases.  Or, to put it another way, a guy legally driving 100 mph is going to encounter fewer obstacles if the left lane is kept clear than if it isn't.

OK, let me understand this.. SOmeone can drive 100 MPH and not keep right, because "Keep right" is a major reason why Germany can have roads without speed limits?

Hmmm.. some new concept here..

[vdeane]

Putting it simple - every single day I see 2-3 idiots insisting on keeping right near exit 7 northbound on Northway. You want to enforce that idiocy?

I would consider moving over so someone can merge in to be a legitimate reason to leave the right lane, as long as one does not stay there for no reason afterwards (people merging from most exits are usually going slower anyways, so it even counts as a pass).  In any case, I-87 would flow a LOT better if people would wait for a gap in traffic big enough for them to not only move over but to accelerate to the speed of the other lane before the people in that lane would have to slow down to "let them in" (if you're changing lanes correctly, nobody will need to let you in, as long as traffic hasn't already jammed up); around here, people usually butt in with no regard for what traffic is doing.  I've seen more people cut someone off at 40 mph than actually use the acceleration lane, for example.  When changing lanes, they have no problem doing so from nearly a complete stop even if the lane they are moving in to is moving at 55, causing traffic in that lane to have to slam on their brakes.  While the Northway certainly has a lot of traffic per lane, IMO a large part of the congestion is caused by people around here not knowing how to merge or change lanes.

Agreed. Just as setting the speed limit too low so that most people speed doesn't change the equation either. I'm not arguing for keeping people with licenses who have lost their ability to drive. I'm pro increasing enforcement of other laws like keeping right except to pass, tailgating, and use of turn signals in place of all speed enforcement.

I would take a once every 5 years trip to court due stupid speed limit rather than daily clusterfuck on the road due to thoughtless "keep right" enforcement

"Keep right" is a major reason why Germany can have roads without speed limits and we can't.

Agreed.  Decently high traffic volumes, generally no more than two or three lanes each direction, top-of-the-line luxury sports cars sharing the road with motor homes, trucks limited to low speeds...  Without people keeping right (or at least moving right when being approached), there would be more accidents.

How all that relates to "no speed limit"?

It relates because in Germany there is a very wide range of speeds encountered on the highway.  With more restrictive speed limits, the range of speeds encountered is narrower, and therefore the frequency of lane use conflict also decreases.  Or, to put it another way, a guy legally driving 100 mph is going to encounter fewer obstacles if the left lane is kept clear than if it isn't.

OK, let me understand this.. SOmeone can drive 100 MPH and not keep right, because "Keep right" is a major reason why Germany can have roads without speed limits?

Hmmm.. some new concept here..

If they're going 100 mph, they're probably spending the majority of their time passing.

[kphoger]

OK, let me understand this.. SOmeone can drive 100 MPH and not keep right, because "Keep right" is a major reason why Germany can have roads without speed limits?

Hmmm.. some new concept here..

If they're going 100 mph, they're probably spending the majority of their time passing.

Exactly.  And did I say something about people not keeping right while going 100 mph?  No, I don't believe I did.  Should read like this:

Someone can drive 100 MPH and not keep right, because "Keep right" is a major reason why Germany can have roads without speed limits.

[kalvado]

Putting it simple - every single day I see 2-3 idiots insisting on keeping right near exit 7 northbound on Northway. You want to enforce that idiocy?

I would consider moving over so someone can merge in to be a legitimate reason to leave the right lane, as long as one does not stay there for no reason afterwards (people merging from most exits are usually going slower anyways, so it even counts as a pass).  In any case, I-87 would flow a LOT better if people would wait for a gap in traffic big enough for them to not only move over but to accelerate to the speed of the other lane before the people in that lane would have to slow down to "let them in" (if you're changing lanes correctly, nobody will need to let you in, as long as traffic hasn't already jammed up); around here, people usually butt in with no regard for what traffic is doing.  I've seen more people cut someone off at 40 mph than actually use the acceleration lane, for example.  When changing lanes, they have no problem doing so from nearly a complete stop even if the lane they are moving in to is moving at 55, causing traffic in that lane to have to slam on their brakes.  While the Northway certainly has a lot of traffic per lane, IMO a large part of the congestion is caused by people around here not knowing how to merge or change lanes.

Did you ever drive from 7 to 87 north?
There is a good 3 lane funneled into 1 lane and another lane from light-controlled entrance (irregular) merged in on top of that.. If you think people merging at that spot can do 55, i think you didn't actually tried that during rush hour. And yes, traffic count of 13k one way and 21k the other way sounds a bit funny.. I would say probably 20K is about right - all merging from 1 lane...
And if we're talking urban/suburban with 1 -2 miles between exits, you need to move over quite often...

Agreed. Just as setting the speed limit too low so that most people speed doesn't change the equation either. I'm not arguing for keeping people with licenses who have lost their ability to drive. I'm pro increasing enforcement of other laws like keeping right except to pass, tailgating, and use of turn signals in place of all speed enforcement.

I would take a once every 5 years trip to court due stupid speed limit rather than daily clusterfuck on the road due to thoughtless "keep right" enforcement

"Keep right" is a major reason why Germany can have roads without speed limits and we can't.

Agreed.  Decently high traffic volumes, generally no more than two or three lanes each direction, top-of-the-line luxury sports cars sharing the road with motor homes, trucks limited to low speeds...  Without people keeping right (or at least moving right when being approached), there would be more accidents.

How all that relates to "no speed limit"?

It relates because in Germany there is a very wide range of speeds encountered on the highway.  With more restrictive speed limits, the range of speeds encountered is narrower, and therefore the frequency of lane use conflict also decreases.  Or, to put it another way, a guy legally driving 100 mph is going to encounter fewer obstacles if the left lane is kept clear than if it isn't.

OK, let me understand this.. SOmeone can drive 100 MPH and not keep right, because "Keep right" is a major reason why Germany can have roads without speed limits?

Hmmm.. some new concept here..

If they're going 100 mph, they're probably spending the majority of their time passing.

And not bothering to return to right lane... Let me see what it looks like.. Oh, yes, split speed limits!

[kalvado]

OK, let me understand this.. SOmeone can drive 100 MPH and not keep right, because "Keep right" is a major reason why Germany can have roads without speed limits?

Hmmm.. some new concept here..

If they're going 100 mph, they're probably spending the majority of their time passing.

Exactly.  And did I say something about people not keeping right while going 100 mph?  No, I don't believe I did.  Should read like this:

Someone can drive 100 MPH and not keep right, because "Keep right" is a major reason why Germany can have roads without speed limits.

Hmmm... SOmeone wants to have a cake and eat it too?

It relates because in Germany there is a very wide range of speeds encountered on the highway.  With more restrictive speed limits, the range of speeds encountered is narrower, and therefore the frequency of lane use conflict also decreases.  Or, to put it another way, a guy legally driving 100 mph is going to encounter fewer obstacles if the left lane is kept clear than if it isn't.

Question is - where that 100 MPH car actually is driving so that he is bothered about obstacles in left lane?