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Old March 15th, 2010, 12:12 AM   #5461
ChrisZwolle
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You bet. The closest state to you with a 70 mph speed limit is West Virginia.

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Old March 15th, 2010, 12:50 AM   #5462
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Quote:
Originally Posted by J N Winkler View Post
AASHTO standards give designers the discretion of choosing a maximum superelevation based on icing, and this is not linked to curve radius, so a curve of given radius at a given design speed can have multiple levels of side friction demand depending on the designer's choice of maximum superelevation.
There are also many other factors that can affect side friction, including pavement type and the vehicle itself.

I haven't seen tables that list the side friction factor in relation to pavement type. My guess would be that longitudinal grinding on PCC would have lower side friction demand than horizontal grinding, and that asphalt would generally have less side friction demand than concrete.

But is it safe to assume that the effects of side friction on pavement type is minimal and therefore disregarded for general roadway design?
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Old March 15th, 2010, 04:33 AM   #5463
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You bet. The closest state to you with a 70 mph speed limit is West Virginia.

Good to see that North and South Dakota as well as Nebraska, all have 75mph speed limit. That's where I'm going to do bulk of my driving this summer. It means I can do at least 80mph
Is limit on rural US highways the same as on the interstates? I can't remember.

I think many rural western counties could follow Texas example and rise limit at least to 80mph. Looking at the map above I can't see difference between counties in Texas wit 80 limit and many counties in let say Wyoming or Nevada.
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Old March 15th, 2010, 04:43 AM   #5464
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Good to see that North and South Dakota as well as Nebraska, all have 75mph speed limit. That's where I'm going to do bulk of my driving this summer. It means I can do at least 80mph
Is limit on rural US highways the same as on the interstates? I can't remember.

I think many rural western counties could follow Texas example and rise limit at least to 80mph. Looking at the map above I can't see difference between counties in Texas wit 80 limit and many counties in let say Wyoming or Nevada.
No, rural highways are almost always 55-65 mph limit. And for good reason, with many uncontrolled intersections. The exception would be long stretches of highway in the middle of nowhere, and some states make exceptions in these cases, such as Nevada.

Last edited by pwalker; March 17th, 2010 at 03:52 AM.
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Old March 15th, 2010, 09:39 AM   #5465
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Originally Posted by geogregor View Post
Good to see that North and South Dakota as well as Nebraska, all have 75mph speed limit. That's where I'm going to do bulk of my driving this summer. It means I can do at least 80mph
Is limit on rural US highways the same as on the interstates? I can't remember.

I think many rural western counties could follow Texas example and rise limit at least to 80mph. Looking at the map above I can't see difference between counties in Texas wit 80 limit and many counties in let say Wyoming or Nevada.
Remember this is the maximum posted, meaning only in a few places even in those states will you find 80 mph posted on a sign. That said people regularly do 80 everywhere on interstates in the west depending on the time of day but if the Dakotas appeal to you have at it. Many times my friends would accidentally reach 100 to 120 mph (160-190 km/h) on interstate 5 in central valley of california simply because people haul ass on that road and you lose track of your speed.
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Old March 15th, 2010, 01:19 PM   #5466
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But is it safe to assume that the effects of side friction on pavement type is minimal and therefore disregarded for general roadway design?
It is--I have certainly never heard of it being taken into account in defining design standards. Most design catalogues aim to limit side friction demand to a certain maximum value which is typically encountered at the least forgiving combination of curve radius and superelevation. The maximum values I have seen are typically around 25%-35% of g (gravitational acceleration) whereas, depending on tire performance, most cars will not start skidding until side friction reaches values of 65% or higher of g.

The problem is that, if you allow small-radius curves, the difference between the design speed and the speed at which a vehicle starts skidding will be smaller. This is our situation in the US compared to Europe.
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Old March 15th, 2010, 09:32 PM   #5467
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Old March 15th, 2010, 09:40 PM   #5468
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Originally Posted by J N Winkler View Post
It is--I have certainly never heard of it being taken into account in defining design standards. Most design catalogues aim to limit side friction demand to a certain maximum value which is typically encountered at the least forgiving combination of curve radius and superelevation. The maximum values I have seen are typically around 25%-35% of g (gravitational acceleration) whereas, depending on tire performance, most cars will not start skidding until side friction reaches values of 65% or higher of g.
Is there a correlation with wet and dry pavement? I was driving in pouring rain today and I can understand cars will skid faster when it's wet, although I think this is mostly limited to interchanges (such as connectors on cloverleafs), not the mainline lanes which are usually straight.
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Old March 15th, 2010, 10:10 PM   #5469
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the Virginia legislature just passed a measure increasing the state speed limit to 70. It probably has the new Governor McDonnell's approval.

...But that doesn't mean any highways will actually have their speed increased from 65...
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Old March 15th, 2010, 10:13 PM   #5470
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Originally Posted by J N Winkler View Post
It is--I have certainly never heard of it being taken into account in defining design standards. Most design catalogues aim to limit side friction demand to a certain maximum value which is typically encountered at the least forgiving combination of curve radius and superelevation. The maximum values I have seen are typically around 25%-35% of g (gravitational acceleration) whereas, depending on tire performance, most cars will not start skidding until side friction reaches values of 65% or higher of g.

The problem is that, if you allow small-radius curves, the difference between the design speed and the speed at which a vehicle starts skidding will be smaller. This is our situation in the US compared to Europe.
There are numerous places in my city where there's a downhill road with a stoplight - in these places the pavement will become crumpled and shoved downhill and very wrinkly and bumpy with cars stopping. I've seen the paint of the stop-bar shoved as much as 6 inches downhill! (Or at least the place where the paint was... what with it being all worn off and all.)

This can even happen with pavement that's only a few years old...
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Old March 15th, 2010, 10:45 PM   #5471
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Quote:
Originally Posted by ChrisZwolle View Post
Is there a correlation with wet and dry pavement? I was driving in pouring rain today and I can understand cars will skid faster when it's wet, although I think this is mostly limited to interchanges (such as connectors on cloverleafs), not the mainline lanes which are usually straight.
The maximum side friction demand is supposed to be well below the level of side friction at which a car will begin skidding in the wet. In fact, if the pavement is well drained with no standing water and no spilled oil, there will not be much difference between wet and dry in the skidding coefficients.

There are basically three mechanisms for skidding in the wet.

* Too much side friction demand (taking curves too fast, etc.)--this will get you in the dry too, though perhaps at a slightly higher speed.

* Aquaplaning (hydroplaning) on poorly drained pavement--this is why crossfall is provided on tangent lengths, and is also why rutting in asphalt pavement is so dangerous (if the ruts get deep enough, the leeward sides will have enough slope to cancel the crossfall, and won't drain; and if the ruts get even deeper, they collect water).

* Oil on top of water at the beginning of a rainstorm--the oil lubricates the tires and reduces static friction, sometimes dangerously so. This is why drivers are urged to slow down and be cautious during the first ten minutes of a heavy rainstorm.

In the UK, design standards call for a 2.5% crossfall on tangent segments and as a consequence, UK motorway pavements drain very well in rainstorms. Crossfall standards in the US vary from state to state. As an example, Kansas is semi-arid and does not get too many heavy thunderstorms, so the crossfall is normally 1.6% for the traveled way and 4% for shoulders. On the other hand, North Carolina gets very heavy and long-lasting thunderstorms in the summer, so much of its Interstate mileage has been built with a steep crossfall (I think 2.5%). States also vary in where the high point is located within the typical cross-section. On freeways in Kansas, the high point for each carriageway normally coincides with the lane stripe between the left-hand and right-hand lane. On old Interstate freeways in NC, the high point is the left edge of the traveled way.
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Old March 16th, 2010, 02:54 AM   #5472
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Remember this is the maximum posted, meaning only in a few places even in those states will you find 80 mph posted on a sign. That said people regularly do 80 everywhere on interstates in the west depending on the time of day but if the Dakotas appeal to you have at it. Many times my friends would accidentally reach 100 to 120 mph (160-190 km/h) on interstate 5 in central valley of california simply because people haul ass on that road and you lose track of your speed.
In my opinion California is the only state where people drive as fast and dynamic as in Europe. Everywhere else I had feeling that people are very relaxed about driving (maybe except NYC). No rush, no stress, slowly.
Once I was stopped by local sheriff in rural Wyoming on the way from Utah to Yellowstone and he told me I was his fifth speeding European that day. For us such low speed limit on such great, wide highways is just an invitation to brake the law People drive much faster on the narrow Alpine roads in Italy or in the Pyrenees.

Anyway I only got a warning as deputy didn't want to spoil my holiday. Thanks.

Quote:
Originally Posted by pwalker
No rural highways are almost always 55-65 mph limit. And for good reason, with many uncontrolled intersections. The exception would be long stretches of highway in the middle of nowhere, and some states make exceptions in these cases, such as Nevada.
Long stretches of highways in the middle of nowhere, that's where I'm going to spend most of my holiday. I like to escape crowded Europe once a year and enjoy open highways of the USA. Can't wait until June.

I love Wyoming, Utah, Idaho, Oregon and of course California (even if people drive like crazy).
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Old March 17th, 2010, 03:29 AM   #5473
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They aren't. The catalogue of available design speeds for Interstates maxes out at 70 MPH. Of course a state DOT or other highway agency can develop a compliant design which has enough "slack" to allow much higher speeds, but as a rule the driver can't count on more than 70 MPH in rural areas.



They aren't and they may in fact be more susceptible to jackknifing because the greater wheelbase of the tractor unit means more of a lever arm. Differential speed limits are unpopular with the trucking industry (especially owner-operators), and car drivers in general have a mixed opinion of them, so in the absence of clear evidence of their safety benefits, many states don't have them. FHWA several years ago sponsored a study to evaluate the safety implications of differential speed limits and was not able to prove that there were any benefits to having them.

This said, I have been told that a number of major trucking firms (Schneider, e.g.) voluntarily govern their tractor-trailers to speeds which are higher than the EU-wide limit of 56 MPH but still slightly below the speed limit for cars in many states--e.g., 62 MPH.
We are now governed at 60 MPH.
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Old March 17th, 2010, 09:48 AM   #5474
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In my opinion California is the only state where people drive as fast and dynamic as in Europe. Everywhere else I had feeling that people are very relaxed about driving (maybe except NYC). No rush, no stress, slowly.
Once I was stopped by local sheriff in rural Wyoming on the way from Utah to Yellowstone and he told me I was his fifth speeding European that day. For us such low speed limit on such great, wide highways is just an invitation to brake the law People drive much faster on the narrow Alpine roads in Italy or in the Pyrenees.

Anyway I only got a warning as deputy didn't want to spoil my holiday. Thanks.



Long stretches of highways in the middle of nowhere, that's where I'm going to spend most of my holiday. I like to escape crowded Europe once a year and enjoy open highways of the USA. Can't wait until June.

I love Wyoming, Utah, Idaho, Oregon and of course California (even if people drive like crazy).
That is an interesting story. I do find that those from other states drive slower, and I have seen many in San Diego (beyond the ubiquitous Arizona plate). It also depends on the time of day as to how "crazy" people are driving. I favor the morning rush hour crowd because everybody tends to go to work within a 2 hour period and they all have a sense of urgency but with skill and the rest of the day is either too leisurely or full of crazy people speeding homeward. At least thats urban. I have gone pretty fast on rural roads outside of California, but I do see your point on the more leisurely pace taken in other states.
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Old March 18th, 2010, 12:17 AM   #5475
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Why 70 Miles Per Hour Is the New 55

Virginia Becomes the Latest State to Raise Its Speed Limit; Drivers in Mississippi Go Really Fast

By JOSEPH B. WHITE

Left to their own devices, American drivers confronted with an open stretch of interstate highway tend to drive at about 70 miles per hour—whatever the legal speed limit happens to be.

Virginia is the 34th state to raise its rural interstate speed limit to 70. WSJ's Joseph B. White says improved car safety was one reason behind the move, but skeptics worry the increase will lead to more fatalities and greater energy use.

That's the finding of an analysis of speed data gathered by TomTom Inc., a marketer of GPS navigation devices. This helps to explain why safety advocates and conservationists are losing the long-running debate over lowering freeway speed limits.

The Virginia legislature last week passed legislation raising the speed limit on rural interstate highways to 70 mph from 65 mph. The state's new Republican governor, Bob McDonnell, put boosting the legal speed limit high on his list of priorities, and got action less than three months after taking office.

Virginia will become the 34th state to boost interstate speed limits to 70 mph or higher. In big, empty states such as New Mexico, Idaho and Nevada, posted limits on rural interstates can be as high as 75 mph.

TomTom collected speed data from 45 states and the District of Columbia, under agreements with customers who agreed to allow the company to collect the information anonymously to improve the quality of its route guidance by directing customers away from congested roads at peak travel times.




The TomTom data suggest that most drivers tend to stay within a few miles per hour of the speed limit on major roads.
In 31 out of the 46 jurisdictions, average freeway speeds ranged between 65 and 70.1 mph.

TomTom found the fastest drivers, on average, in Mississippi, where interstate drivers average 70.1 mph, or a hair over the maximum posted limit. The company doesn't have speed data from some sparsely populated states, including Montana, where drivers may be moving faster than those in Mississippi, says Nhai Cao, senior product manager for TomTom's SpeedProfiles database.

Virginia drivers clock in at a law-abiding 65 mph. The slowest drivers—drumroll, please—are in Washington, D.C. Freeway traffic in the nation's congested capital crawls at an average of 46.4 mph, according to TomTom's data. That may explain the eagerness of Virginia residents who work inside the Beltway for the freedom to go faster when they finally see some open road.

Hawaii is the slowest state, with highway drivers traveling at an average 52.7 mph.

Speed limits and enforcement have taken a symbolic significance that transcends vehicle mechanics or highway design.

The 55 mph national speed limit enacted in 1973 in response to the first Arab oil embargo was justified as a means of conserving fuel. In 1987, the law was changed to allow speeds up to 65 mph. But the Republican Congress elected in 1994 did few things more popular than repealing the limit altogether in 1995.

Driving speed has become a proxy for bigger questions about personal freedom versus government control.

The argument for raising speed limits is fundamentally an argument for letting drivers use their own judgment. The argument for stronger speed control is that too many people behave badly behind the wheel.

Insurers and other safety advocates, including groups such as the Governors Highway Safety Association, have consistently called for motorists to slow down, and for state and local authorities to get tougher on speeding enforcement.

"Higher speeds are bad on any road," says Anne McCartt, vice president of research for the Insurance Institute of Highway Safety, a research arm of the insurance industry.

The Federal Highway Administration estimates that in 2008, about 31% of the total 37,261 highway fatalities were related to speeding over posted limits.

But advocates of relaxing speed limits point to federal statistics which show that both fatalities and fatality rates on U.S. highways are declining even as speed limits rise.

The U.S. Department of Transportation last week reported that its latest estimate of highway deaths in 2009 is 33,963—the lowest number since the government began keeping these grim records in 1954. The fatality rate is estimated at 1.16 deaths per 100 million vehicle miles traveled.


Modern cars and light trucks have an average of 225 horsepower under the hood and sophisticated safety systems such as traction control. They are designed to cruise comfortably, safely and efficiently at between 65 and 70 mph—if not faster, particularly in the case of the autobahn-burners German luxury brands sell.

If gas prices spike again this summer, as some predict, the idea of dropping speed limits again may get a new hearing. But Virginia's decision and the powerful cars consumers are buying suggest otherwise.

Write to Joseph B. White at [email protected]


Last edited by Gaeus; March 18th, 2010 at 02:10 AM.
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Old March 18th, 2010, 01:06 AM   #5476
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Alabama transportation officials to close section of I-65 north in Morgan County Thursday
By Ginny MacDonald -- The Birmingham News
March 17, 2010, 2:51PM

Alabama transportation officials will close a section of Interstate 65 north in Morgan County at milemarker 329 between Hartselle and Priceville Thursday for crews to repair a sinkhole.

Northbound traffic will be directed off I-65 north at exit 318 at Lacon onto U.S. 31, then north to Alabama 67 and back onto I-65 at exit 334 at Priceville.

Oversized loads traveling north will get off the interstate at exit 310 to Alabama 157, onto Alabama 24 to Moulton, and then to Alabama 20 and back to I-65 at exit 340 at the I-65/I-565 interchange.

ALDOT engineers will conduct repairs as quickly as possible, officials say.

Motorists are requested to consider using alternate routes, adjust arrival/departure times, slow down, observe signs and message boards, and use extreme caution in this area.
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Old March 18th, 2010, 11:16 PM   #5477
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As far as I can:

In Poland, on the road in force 50 km / h
In Poland, on the roads outside the city in force 90 km / h
As a two-band and 100 km / h
Highway is 130 km / h.

But the application of the law is on our others. driving at speeds not catch you unless they really masters the bores.

In Poland, on the road in force 80 km / h
In Poland, on the roads outside the city spaces of 110 km / h
As a two-band and 130 km / h
Highway is 160 km / h.
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Old March 19th, 2010, 03:20 AM   #5478
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???????
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Old March 19th, 2010, 06:09 AM   #5479
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http://blog.al.com/spotnews/2010/03/...ds_on_int.html


Alabama lowering speeds on Interstate 20 near Georgia after rock from pothole fatally injures traveler
By The Birmingham News
March 18, 2010, 12:35PM

Alabama Transportation officials are lowering the speed limit on Interstate 20 from Oxford to the Georgia state line following a fatal accident Monday, the Anniston Star reports.

The speed limit will drop from 70 mph to 55 mph from mile marker 182 to the state line. Extra troopers will patrol the stretch, according to the newspaper. Jo Maureen Fisher of Goose Creek, S.C., died in a Birmingham hospital Tuesday, hours after a vehicle hit a pothole and threw a rock that passed through the windshield of the car Fisher was in and struck her in the head.
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Old March 19th, 2010, 07:11 AM   #5480
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That's a sad story. Yet another example of our crumbling infrastructure not being looked after properly.

This is the best way to remedy the situation, though. Lower the speed limits to a safe speed and heavily patrol it. Only then will people be willing to fork over the money necessary to keep our infrastructure up. (I don't mean to politicize her death, but this very political issue is becoming life or death!)
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