5-10mph over or go the speed limit?
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From: Maryland
per·cen·tile
pərˈsenˌtīl/
noun
STATISTICS
pərˈsenˌtīl/
noun
STATISTICS
- each of the 100 equal groups into which a population can be divided according to the distribution of values of a particular variable.
- each of the 99 intermediate values of a random variable that divide a frequency distribution into 100 groups.
"the tenth percentile for weight"
- each of the 99 intermediate values of a random variable that divide a frequency distribution into 100 groups.
The question you need to ask is on average how are the speed limits set relative to the 85th percentile speed on my highways where I live, the answer is on most roadways when there is free flowing traffic they are consistently 10-20MPH below the 85th percentile speed.
Examples:
I-270 in Montgomery County, limit is 55, today I was doing 80 coming back from Frederick and I was definitely at or below the 85th percentile speed at that time. Typically I would say the 85th percentile speed for 270 south of Germantown is about 70 MPH. Limit should be 70.
Free flowing traffic on 495 (the beltway) is similar, limit should be 65-70.
MD-200 (the ICC) limit is 60, 85th percentile speed is probably 65-70 because of HEAVY enforcement. When there is no enforcement it can run all day at 75-80. Limit should be 70. Enforcement is entirely revenue driven, its patrolled by the MTA Police who only patrol toll roads in MD.
Last edited by SW17LS; Jun 28, 2018 at 06:46 PM.
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From: ON/NY
I don't think you're getting what a percentile is. 85% of people are always driving at or below the 85th percentile speed, and 15% of people are always driving faster. Thats what a percentile is. If people were "driving slower than" or "driving faster than" then the 85th percentile would change to fit that data set.
So on any given day or time of day the 85th percentile speed will vary based on conditions, traffic, etc.
The question you need to ask is on average how are the speed limits set relative to the 85th percentile speed on my highways where I live, the answer is on most roadways when there is free flowing traffic they are consistently 10-20MPH below the 85th percentile speed.
Examples:
I-270 in Montgomery County, limit is 55, today I was doing 80 coming back from Frederick and I was definitely at or below the 85th percentile speed at that time. Typically I would say the 85th percentile speed for 270 south of Germantown is about 70 MPH. Limit should be 70.
Free flowing traffic on 495 (the beltway) is similar, limit should be 65-70.
MD-200 (the ICC) limit is 60, 85th percentile speed is probably 65-70 because of HEAVY enforcement. When there is no enforcement it can run all day at 75-80.
So on any given day or time of day the 85th percentile speed will vary based on conditions, traffic, etc.
The question you need to ask is on average how are the speed limits set relative to the 85th percentile speed on my highways where I live, the answer is on most roadways when there is free flowing traffic they are consistently 10-20MPH below the 85th percentile speed.
Examples:
I-270 in Montgomery County, limit is 55, today I was doing 80 coming back from Frederick and I was definitely at or below the 85th percentile speed at that time. Typically I would say the 85th percentile speed for 270 south of Germantown is about 70 MPH. Limit should be 70.
Free flowing traffic on 495 (the beltway) is similar, limit should be 65-70.
MD-200 (the ICC) limit is 60, 85th percentile speed is probably 65-70 because of HEAVY enforcement. When there is no enforcement it can run all day at 75-80.
No. I do understand what it is, I looked into it. You come across as a little bit confusing. Do you not think that Washington DC calculates speed limits based on the 85 percentile?
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From: Maryland
To be clear, there are very few highways in "Washington DC", the bulk of the roads I'm talking about are in the states of Maryland and Virginia.
Its actually been in the news with MD-200 the ICC. When the road opened (its a newly constructed toll road) the limit was 55. The road is lightly travelled, and except for the very beginning, quite wide and smooth with good sightlines, very hard to drive the speed limit. The road is HEAVILY enforced, more enforced than any road around here I've ever seen. Its 19 miles long, and its not unusual to see 5-6 police officers in speed traps as well as rolling enforcement. This enforcement is used to pay for the road on top of a high toll.
Public outcry made them re-evaluate the speed limit and they raised it to 60 citing a study that showed the 85th percentile speed was 60, well its artificially low because of the crazy high enforcement. There are multiple ongoing lawsuits with the state over it.
Lexus Fanatic
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From: Maryland
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From: ON/NY
No, I do not believe the speed limits set on these roads are set based on the 85th percentile speed, they are set artificially low. I truly don't see whats confusing here if you know what a percentile is...
To be clear, there are very few highways in "Washington DC", the bulk of the roads I'm talking about are in the states of Maryland and Virginia.
Its actually been in the news with MD-200 the ICC. When the road opened (its a newly constructed toll road) the limit was 55. The road is lightly travelled, and except for the very beginning, quite wide and smooth with good sightlines, very hard to drive the speed limit. The road is HEAVILY enforced, more enforced than any road around here I've ever seen. Its 19 miles long, and its not unusual to see 5-6 police officers in speed traps as well as rolling enforcement. This enforcement is used to pay for the road on top of a high toll.
Public outcry made them re-evaluate the speed limit and they raised it to 60 citing a study that showed the 85th percentile speed was 60, well its artificially low because of the crazy high enforcement. There are multiple ongoing lawsuits with the state over it.
To be clear, there are very few highways in "Washington DC", the bulk of the roads I'm talking about are in the states of Maryland and Virginia.
Its actually been in the news with MD-200 the ICC. When the road opened (its a newly constructed toll road) the limit was 55. The road is lightly travelled, and except for the very beginning, quite wide and smooth with good sightlines, very hard to drive the speed limit. The road is HEAVILY enforced, more enforced than any road around here I've ever seen. Its 19 miles long, and its not unusual to see 5-6 police officers in speed traps as well as rolling enforcement. This enforcement is used to pay for the road on top of a high toll.
Public outcry made them re-evaluate the speed limit and they raised it to 60 citing a study that showed the 85th percentile speed was 60, well its artificially low because of the crazy high enforcement. There are multiple ongoing lawsuits with the state over it.
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From: Maryland
Well. I have to disagree with you. The vast majority of travel I have done, the speed limits seem appropriate. It is very easy to go a little over the speed limit on the highway. The last long trip I made was down to Virginia beach, to Savanagh back to Washington and then home to New York State and finally Toronto. The vast majority of the way was 70MPH speed limit and it was very easy to go 75 or even 80. Your mileage may differ on your local area but the majority of travel for me was quite fine. I am really not sure why you are so obsessed or perturbed by all of this.
BUT, if the 85th percentile speed on those roads is 75 or 80, 70 is still too low. Its not as big an issue as a roadway with a 55 MPH limit where the 85th is 70 or 75 though. With a 70 MPH limit one can drive with the flow and stay within the typical 10MPH "enforcement buffer" so those don't really bug me. However, today I was at the flow of traffic and I was 25MPH over the limit...thats crazy.
Note, I didn't call out any 70 MPH limit roads in my examples.
You can't really disagree with me about the roads I drive on every day and that you maybe drove on once...
I'm not obsessed or perturbed. I didn't start this thread I'm just participating in it. If the topic doesn't interest you, bow out. Why does it bug me? Because on these roads in order to not break the law I have to make myself and those around me less safe, and thats not right.
Last edited by SW17LS; Jun 28, 2018 at 07:10 PM.
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From: ON/NY
You can't really disagree with me about the roads I drive on every day and that you maybe drove on once...
I'm not obsessed or perturbed. I didn't start this thread I'm just participating in it. If the topic doesn't interest you, bow out. Why does it bug me? Because on these roads in order to not break the law I have to make myself and those around me less safe, and thats not right.
Lexus Fanatic
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From: Maryland
Whether you believe me or not, I was doing 80, totally within the flow of traffic today on I-270 and the speed limit was 55. That’s 25 MPH over the limit. It’s not unusual at all for that stretch of 270 either. Are you calling me a liar?
Im glad you’ve visited here and found the speed limits appropriate, I’ve driven hundreds of thousands of miles on these roads though, so folks can decide who’s viewpoint has more merit on speed limits and my local roads.
Im glad you’ve visited here and found the speed limits appropriate, I’ve driven hundreds of thousands of miles on these roads though, so folks can decide who’s viewpoint has more merit on speed limits and my local roads.
Lexus Fanatic
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From: ON/NY
Lexus Fanatic
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From: Maryland
If I was driving along at 55 MPH, THAT would have been unsafe.
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From: ON/NY
Lexus Fanatic
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From: ON/NY
Not calling you a liar. Just trying to pin point everything. I have never ever seen a highway where the regular flow of traffic is 25MPH over the speed limit, some of the lanes yes. But not all of them . I almost want to say, how long of a drive is this highway that is going 25MPH? It seems unbelievable. I would understand if you said the left lane was going 25MPH, but then I would wonder if there were anyone going the speed limit at all.
Most I have ever seen, is the left lane is going 15-20 MPH on average for long long stretches. The rest of the highway is going either the speed limit of just barely over. Never have I driven on a two lane or three lane highway where the whole flow was going 25MPH for long stretches.
Most I have ever seen, is the left lane is going 15-20 MPH on average for long long stretches. The rest of the highway is going either the speed limit of just barely over. Never have I driven on a two lane or three lane highway where the whole flow was going 25MPH for long stretches.
Last edited by Toys4RJill; Jun 28, 2018 at 07:39 PM.
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From: Virginia/D.C. suburbs
So have I. Most of my driving, in my 40-year-span behind the wheel, has been in the Mid-Atlantic area, with occasional longer trips. I agree partly with you and partly with Jill.
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From: Maryland
Not calling you a liar. Just trying to pin point everything. I have never ever seen a highway where the regular flow of traffic is 25MPH over the speed limit, some of the lanes yes. But not all of them . I almost want to say, how long of a drive is this highway that is going 25MPH? It seems unbelievable. I would understand if you said the left lane was going 25MPH, but then I would wonder if there were anyone going the speed limit at all.
Now, that’s not typical, but being able to do that at 70-75 is very typical. You really can’t go 55 safely unless you are in the local lanes. Down south from that stretch the exits are confined to another divided area to the right. There is NO reason why 270 north of the start of the local lanes or the express lanes all the way down shouldn’t have a speed limit of at least 65, and 270 where it does go to 65 should go to 70.
Theres an area on the Beltway too east of 95 towards PG County and the BW Parkway where it gets the same way. Whole road screams at 75-80 and the limit is 55.