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Birdwatching
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German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 10:21 am

Bit of a random topic, but after living for years in the US and in Germany, I have noticed how the on-ramps to highways (limited access 4-lane roads) are typically very different in both countries (there are exceptions in both directions)

Here's what I mean:

Typical US design, the ramps will go from both sides of the secondary road. This saves space, is easier to drive, I'd expect less accidents, and in many cases if the secondary street crosses over a bridge, you accelerate downhill to get to highway speed, and decelerate uphill. I LOVE this design.


In Germany, you'll typically find this design: Super tight curves that go down (or up) to the highway, you'll have to go really slow and then speed up like a madman. I'm sure these are much more dangerous for accidents, and they actually use MORE space than the super slim on ramps pictured above.


WHY, WHY, WHY?? Why would you, as an engineer, EVER use the curvy design when you could just as well use the other one? Don't tell me it's about the limited space in Europe, as the German design (in my opinion) uses more space than the other one.

Your opinions?

Soren   
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Kiwirob
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 10:28 am

Quoting Birdwatching (Thread starter):
Super tight curves that go down (or up) to the highway, you'll have to go really slow and then speed up like a madman.

Giving it some welly on those tight curves is fun and a challenge to get it just right.
 
TheCommodore
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 10:42 am

Well,

Not sure about which is safer, German or US. Check out the accident rate between both countries, per capita of Pop.

http://en.wikipedia.org/wiki/List_of...ries_by_traffic-related_death_rate

Here is a link, it is about death related accidents, not just accidents but none the less.

Germany, 4.5 deaths per 100,000 inhabitants, compared to the USA, 12.3 deaths per 100.000 inhabitants.

That aside, the Germany ones look nicer, at least from the aerial photography that is  

[Edited 2011-03-04 02:43:43]
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MD11Engineer
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 10:53 am

I think the main reason is that when you get off the Autobahn, the kurve forces you to slow down. Else there exists too much temptation to continue with Autobahn speed on the normal road (if you have ever driven for several hours at 120 + km/h, you´ll suddenly find normal roadspeeds like crawling.

In your example for the German intersection there are also houses where the second ramp of the American system would go.

In any case, if necessary you´ll have to slow down or stop at the BEGINNING of the acceleration lane to look for a suitable gap in the slow lane BEFORE accelerating to join the traffic on the Autobahn.

Jan
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Klaus
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 12:06 pm

Quoting MD11Engineer (Reply 3):
I think the main reason is that when you get off the Autobahn, the kurve forces you to slow down.

Only in one of the two directions. That's not it.

My guess would be that it can mean less construction effort: Only two slightly wider ramps will have to be built instead of four just slightly narrower ones.

And this form is a bit more flexible in tighter spaces when it can be put to either side, depending on circumstances.

We've got the other form as well, it's just not the only one.
 
PanHAM
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 12:20 pm

With a good driver education one can very easily manage both. As mentioned already, we got both types of highway access and depending on the local conditions. Germany is a bit smaller than the US and existed with build-up areas long before cars came and roads were needed.

Take the picture above, leaving in north western direction you have to enter the tight curve, entering in the same direction you can accelerate as you please. In the southern direction its the other way round.

Both exit and access offer enough slow down resp acceleration lanes, on Autobahns usually 300 meter. And it is really fun to drive the tight curves AND we have the cars t do it.
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Klaus
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 12:23 pm

Quoting PanHAM (Reply 5):
AND we have the cars t do it.

You just had to rub it in, didn't you...?   
 
Quokka
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 12:44 pm

There are numerous forms of junctions in Germany and the layout takes into consideration a host of factors , including but not limited to, angle of the intersecting roads/ highways, types of roads that are at the intersection (an intersection of two stretches of Autobahn would be very different to that of an Autobahn and a relatively minor road),amount of space, built and natural environment, traffic densities and volumes, noise, site preparation, cost and other factors. No doubt such factors exist in the US as well and we also see various types of intersections there as well.
 
PanHAM
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 1:15 pm

Quoting Klaus (Reply 6):
Quoting PanHAM (Reply 5):
AND we have the cars t do it.

You just had to rub it in, didn't you...?

yesss  
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Charles79
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 1:52 pm

Quoting PanHAM (Reply 5):
And it is really fun to drive the tight curves AND we have the cars t do it.

You are right about this statement...having visited Germany 7 times now I have thoroughly enjoyed BOTH driving on the Authobahn AND driving cars that actually drive and handle like...cars!

In response to the OP, it also has to do, I think, with the age of the system. The US Interstate network dates from the 50's, with some of the sections in western states being only 20 years old at most. The availability of space is also an issue, and again the layout you presented is more prevalent in southern and western states where space wasn't at a premium as in the Northeast. For instance, I lived in Connecticut for 5 years and in that state you find all types of on- and off-ramps, even left-lane exits! The style is more or less dictated by the availability of space (be it because of the terrain or existing development), funds, and who knows, maybe even local preferences.

In the end, though, any driver with proper training should be able to handle either situation. I have driven on both systems quite extensively and don't find either one particularly more challenging or worse to drive on than the other one.

Charles
 
rfields5421
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 2:05 pm

Quoting Charles79 (Reply 9):
The US Interstate network dates from the 50's,



I think a lot of the 'challenging' on/off ramps are older ramps.

When the US Interstate system was first built - the IDEAL on/off ramp configuration was the cloverleaf with four 270 degree turns for on/ off ramps. The join lane on the main freeway was less than 100 yards long.

Over the years, the US has learned such ramps are not very safe, they are not supportive of good traffic flow and that the type ramp you show above is better. At a cost of 100s of billions of dollars, many older ramps have been demolished and replaced. That process is continuing today.

I suspect, but do not know, that many of the worst ramps in Germany were first built over 50 to 80 years ago. I would like to see a comparison of a completely new entrance/ exit ramp built in Germany in the past 10 years.
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FlyDeltaJets87
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 2:19 pm

Quoting Birdwatching (Thread starter):
Your opinions?

The US hasn't figured it out in many places. For one, many areas still lack long acceleration and merge lanes. Nothing like coming down a ramp (no matter what speed your at), and having dump straight in the freeway. Hope there's not a semi-truck there. Second, many areas have similar layouts to your German example, especially in major cities. The worst, IMO, is when it's a four clover-leaf style exit where the acceleration lane from the "On-Ramp" is the same lane as the deceleration lane for the "Off Ramp". You come up the on-ramp around the curve at 20-30 mph and have highway traffic flying along at 60-70 mph, little time to accelerate and get over because if you stay in the lane, you'll be right back on the off-ramp, and you have some of that traffic that's doing 60-70 mph trying to get in your lane so they can get off at the exit. I HATE the interstate highways in Ohio for both of these reasons.
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sebolino
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 2:21 pm

The difference is obvious. In the "curvy" design you never cross a road, you just enter or exit the highway on your right and enters or exit the other road on the right. It's the most common used for highways in France.

In the first design, you have to enter a crossroad with redlights or stop signs when you get out of the highway, possibly at full speed. This is the design used for the peripheric highway around Paris. I 'm not sure it's safer, but for sure it needs less space.
 
PanHAM
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 2:25 pm

Quoting rfields5421 (Reply 10):
suspect, but do not know, that many of the worst ramps in Germany were first built over 50 to 80 years ago. I would like to see a comparison of a completely new entrance/ exit ramp built in Germany in the past 10 years.

all of the very old on/off ramps in Germany have been rebuilt. You won't find a single one of the original Autrobahn ramps in the country. The last of the "tricky" ones i can remeber were some of the Aschaffenburg exits and the are all new now.
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Super80DFW
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 2:51 pm

Quoting Birdwatching (Thread starter):
WHY, WHY, WHY?? Why would you, as an engineer, EVER use the curvy design when you could just as well use the other one?

I'm willing to bet the engineer drives a BMW equipped with some kind of sport suspension, so he probably loves the german on-ramps!

But really, in the german picture, on the SE corner of the intersection there appears to be a building of some sort very close to the corner. Possibly that has something to do with it in this instance, and maybe many more?
 
NoUFO
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 2:52 pm

Quoting Birdwatching (Thread starter):
Your opinions?
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1337Delta764
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 2:55 pm

Of course, the ideal design is the multi-level stack interchange, as they can handle the most traffic and do not require signaling.

 
ALTF4
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 4:14 pm

They've been re-doing a lot of the ramps around here to be the cloverleaf style. I have mixed feelings, as others have said. The cloverleaf cuts down on congestion, as the traffic can continously flow onto the ramp without waiting at a light (the one pictured in the OP is only a half cloverleaf - real ones have another half on the other side of the secondary road). On the other hand, though, trying to merge soon enough to not get forced back off while not getting rammed by some idiot going 80mph in the exit lane... well... it can get messy.

That said, ramp metering makes a mess out of everything, though, because the meters are slow enough that a traffic light would not affect the ramp traffic. Also, metering traffic only 100 feet before the merge is a stupendously stupid idea, because you get up to 25 mph after flooring it, only to merge into 80 mph traffic.
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Fly2HMO
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 4:22 pm

Quoting TheCommodore (Reply 2):
compared to the USA, 12.3 deaths per 100.000 inhabitants.

That just goes to show that 99% of my fellow countrymen just don't know how to drive.  

Many freeways and interstates are just as good if not better than the autobahn, yet people still manage to kill themselves. It would help if getting your license in the US took more than just having a heartbeat and the capability to breathe.
 
ALTF4
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 4:35 pm

Quoting Fly2HMO (Reply 18):
It would help if getting your license in the US took more than just having a heartbeat and the capability to breathe.

Hey now, I had to be able to turn this thing called a "steeling wheel" or a "steering wheel" or something like that. At any rate, the lady told me it "makes the car go where you want it to go".

I had to unhitch my house from the back of my car, though, before I could take the test.




/s
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Moose135
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 4:46 pm

Quoting PanHAM (Reply 13):
all of the very old on/off ramps in Germany have been rebuilt. You won't find a single one of the original Autrobahn ramps in the country.

I believe the 8th Air Force helped with that effort in the mid-1940s.  
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PanHAM
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 5:06 pm

Quoting moose135 (Reply 20):
I believe the 8th Air Force helped with that effort in the mid-1940s

no, they rather took charge of the city centres. The old exit/entry ramps at aschaffenburg were still there into the late 90s early 2000s
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aero145
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 5:25 pm

I can and can not understand your rant.

Of course it’s not comfortable to have to “accelerate like a mad man” while driving onto the Autobahn, but I cannot understand why you don’t mention the very common cloverleaf interchanges. This one is maybe not a real cloverleaf interchange, but it’s annoying enough to drive KA-Damm into the east and onto the A565 into the north or A565 into the north onto KA-Damm into the west.


courtesy of Maps.Google.de

When coming off A565, I sometimes have to put the pedal to the metal to go past accelerating cars on the right lane, and sometimes I have to brake heftily after accelerating a bit while entering the Autobahn because of people coming off the Autobahn that drive with 100 km/h.

The cloverleafs are IMO the only intersections that shouldn’t exist, because of the collision hazard. The others may be annoying, but not as dangerous.

To date I haven’t had any real problems with the cloverleafs, but I’ve been in a car where the driver didn’t really understand the concept and we were only lucky that the other driver had a quick reflex, otherwise we would have been pretty screwed.
 
travelin man
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 5:51 pm

The US probably has as many variations in interchanges as Germany does. Heck, just in Los Angeles you have:
Cloverleaf:


Half Cloverleaf:


Diamond:


I Don't Know What You Call It:


Standard Freeway:


Crazy Freeway:


East LA Interchange:
 
DAL767400ER
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 5:58 pm

Quoting travelin man (Reply 23):
I Don't Know What You Call It:

Looks like a regular SPUI (Single Point Urban Interchange) with some lane weaving to the west of the interchange.
 
aero145
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 6:06 pm

Quoting travelin man (Reply 23):
Half Cloverleaf:

Albeit not including the crossing of the traffic flows like in my example, yours only has a loop while driving onto the freeway, not driving off it – I could live with those.
 
chrisair
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 6:33 pm

Quoting travelin man (Reply 23):
Heck, just in Los Angeles you have:
Cloverleaf:

This is probably a better example:

http://img823.imageshack.us/img823/9640/screenshot20110304at113.png
 
LH526
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 6:52 pm

... nuff said  
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N1120A
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 7:12 pm

Quoting Birdwatching (Thread starter):
and in many cases if the secondary street crosses over a bridge, you accelerate downhill to get to highway speed, and decelerate uphill.

There is plenty of the opposite too.

Quoting Charles79 (Reply 9):
The US Interstate network dates from the 50's, with some of the sections in western states being only 20 years old at most

The German network is older, but they actually spend money on infrastructure there.

Quoting ALTF4 (Reply 17):
Also, metering traffic only 100 feet before the merge is a stupendously stupid idea, because you get up to 25 mph after flooring it, only to merge into 80 mph traffic.

The point of metering is that you do it at times where the traffic isn't going fast, in order to control congestion.
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Glom
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 9:01 pm

Quoting ALTF4 (Reply 17):
They've been re-doing a lot of the ramps around here to be the cloverleaf style.

They're putting in cloverleaf interchanges? I thought they were supposed to be taking them out because of the horrendous weaving problems they cause. At least partially unroll it, like at the interchange of the M40 and M25.

View Larger Map
 
Glom
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RE: German Vs US Highway On-Ramps (RANT)

Fri Mar 04, 2011 9:11 pm

Quoting N1120A (Reply 28):
The German network is older, but they actually spend money on infrastructure there.

Boo hoo! This is what our level of spending gets us.

An incomplete 4 level stack where some movements requires ratrunning via an A-road.

View Larger Map

The 3 level stacked roundabout interchange.

View Larger Map

[Edited 2011-03-04 13:12:29]
 
travelin man
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 12:50 am

Quoting Glom (Reply 29):
They're putting in cloverleaf interchanges? I thought they were supposed to be taking them out because of the horrendous weaving problems they cause.

Here in SoCal they've been taking OUT the cloverleaf freeway interchanges.

The 60/215/91 interchange used to be a traditional full cloverleaf, but they rebuilt it a year or two ago and replaced two of the cloverleafs with flyovers:


The 5/55 interchange was also completely rebuilt from a traditional cloverleaf (you can still kind of see where the old cloverleafs used to be):


Cloverleafs are really not a good design for interchanges of two freeways with high speed lane changes.
 
signol
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 1:32 am

This site:
http://www.cbrd.co.uk/interchanges/diamond.shtml
has some good descriptions of the various junction types.

signol
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DfwRevolution
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 4:31 am

Quoting TheCommodore (Reply 2):
Not sure about which is safer, German or US. Check out the accident rate between both countries, per capita of Pop.

Germany, 4.5 deaths per 100,000 inhabitants, compared to the USA, 12.3 deaths per 100.000 inhabitants.

Deaths per inhabitant is a just about meaningless if the population of one country drives significantly more than the other. Normalize for kilometers driven, and Germany suffers 7.2 fatalities billion km versus 8.5 per billion km in the USA. That's a whopping 18% difference rather than the 270% you tried to portray. These are numbers from your own source.

Lots of factors could easily account for an 18% difference that have nothing to do with engineering competence or driver skill. For example, rural undivided roads in any country are going to be less safe than divided controlled access freeways. If Americans drive more miles on rural roads, that will slant the statistics against the US. Only 12% of Germany's population lives in rural areas compared to 20% of Americans. Seems like that is probably a safe assumption.

Even the faulty per capita numbers you provided are determined by averaging fatalities over millions of people. It would make no sense to use such an average to conclude that any given highway design in Germany is safter than any given highway design in the U.S. You could basically find an untrafficed intersection in Germany and leave the traffic lights green in all directions without even budging the fatalities per capita for Germany. Would you take a snapshot of that intersection and hold it as safer than a U.S. intersection because of the per capita fatality statistic is lower for Germany?

Quoting Birdwatching (Thread starter):
Typical US design, the ramps will go from both sides of the secondary road. This saves space, is easier to drive, I'd expect less accidents, and in many cases if the secondary street crosses over a bridge, you accelerate downhill to get to highway speed, and decelerate uphill. I LOVE this design.

I happen to agree 100%. While this design is common in the U.S., it is not universal. The interstate highways in New York happen to use the "German" style on/off-ramps. I they make it considerably easier to enter the wrong direction of traffic, especially if you are unfamiliar with the particular intersection. They also make it more difficult to access road-side services like gas stations, restaurants, shops, or hotels.
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mham001
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 4:31 am

Quoting Fly2HMO (Reply 18):
That just goes to show that 99% of my fellow countrymen just don't know how to drive.

It might be more accurate to compare deaths with miles driven. I read today Americans drove 3 trillion miles last year.

California is phasing out cloverleafs. They have mostly settled on the frontage road style or whatever its called. It uses less space overall. I like cloverleafs, in some places its the only chance you get to go around a curve. its nice for making highway u-turns too without stopping.
 
DfwRevolution
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 4:42 am

Quoting N1120A (Reply 28):
The German network is older, but they actually spend money on infrastructure there.

And the $300 billion we spend per year is chopped liver?
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N1120A
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 5:47 am

Quoting dfwrevolution (Reply 33):

Deaths per inhabitant is a just about meaningless if the population of one country drives significantly more than the other. Normalize for kilometers driven, and Germany suffers 7.2 fatalities billion km versus 8.5 per billion km in the USA. That's a whopping 18% difference rather than the 270% you tried to portray. These are numbers from your own source.

Meanwhile, the US has ridiculously low speed limits on its highways, while Germany has vast portions that are unlimited and still more that are 130 km/h. The only US highways that come close are the 80 mph/128 km/h portions of Interstates 10 and 20 in extremely sparsely populated portions of Texas.

Quoting dfwrevolution (Reply 35):

And the $300 billion we spend per year is chopped liver?

Except, of course, that you claim we spend nearly twice than we actually do. If we spent $300 million a year, we might actually get things done.

http://www.cbo.gov/ftpdocs/120xx/doc...43/01-19-HighwaySpending_Brief.pdf
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DfwRevolution
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 3:03 pm

Quoting N1120A (Reply 36):
Except, of course, that you claim we spend nearly twice than we actually do. If we spent $300 million a year, we might actually get things done.

The $146 billion in your source is just for highways. We spend money on lots of other types of infrastructure, too.

Quoting N1120A (Reply 36):
Meanwhile, the US has ridiculously low speed limits on its highways, while Germany has vast portions that are unlimited and still more that are 130 km/h. The only US highways that come close are the 80 mph/128 km/h portions of Interstates 10 and 20 in extremely sparsely populated portions of Texas.

We've already established that controlled access highways are safer than uncontrolled roads, which due to the demographics of the U.S., more Americans drive on than Germans.
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MD11Engineer
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 3:29 pm

Quoting dfwrevolution (Reply 37):
We've already established that controlled access highways are safer than uncontrolled roads, which due to the demographics of the U.S., more Americans drive on than Germans.

You haven´t been to Germany lately? We have a lot of rural regions without Autobahn acccess. I drive 25 km to work and back every day on such roads (called Landstrasse in German). Most of them have only one lane in each direction. Maximum speed is 100 km/h.
Depending on where they are, they are often curvy (especially in the hills and mountains) and bordered by ditches and trees.
Jan
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1337Delta764
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 6:00 pm

Quoting Glom (Reply 29):
They're putting in cloverleaf interchanges? I thought they were supposed to be taking them out because of the horrendous weaving problems they cause. At least partially unroll it, like at the interchange of the M40 and M25.

My guess is that they are actually putting in stack interchanges, not cloverleafs. I have met some people who think the Big I (I-25/I-40 interchange) in Albuquerque is a cloverleaf, when in truth it is a 5-level stack interchange.
 
aa757first
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 6:15 pm

Quoting ALTF4 (Reply 17):
That said, ramp metering makes a mess out of everything, though, because the meters are slow enough that a traffic light would not affect the ramp traffic. Also, metering traffic only 100 feet before the merge is a stupendously stupid idea, because you get up to 25 mph after flooring it, only to merge into 80 mph traffic.

80 MPH traffic? I wish. When highways go on meter here in Northern California, traffic is going 35 MPH on a good day.

Quoting Fly2HMO (Reply 18):
That just goes to show that 99% of my fellow countrymen just don't know how to drive.

Many freeways and interstates are just as good if not better than the autobahn, yet people still manage to kill themselves. It would help if getting your license in the US took more than just having a heartbeat and the capability to breathe.

I was surprised when riding on the Autobahn. I thought California's highways were far safer and better designed. I'd much rather be going 110 MPH on the I-880 (I don't) than 110 MPH on the segments of the Autobahn I was on.

But, like you said, Americans can't drive. Its not our fault, really, since our license tests are a joke. In PA, you have to answer 15 out of 18 multiple choice questions on a computer, complete 50 hours of driving with a parent and then take your driver's test. I had to put on my hazard lights, honk my horn, parallel park and drive around the block. One driving license center would just make kids drive around the parking lot if it was raining because they didn't want them out on the road.

Kind of scary to look back on the way I drove when I was 16...and I was one of the better drivers I knew.
 
rfields5421
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 6:30 pm

One question about the original post - the German example looks to me like many in the US which were built for Toll Roads - with space to allow vehicles stopping to make payment at a toll booth for both entrance and exit to not back up traffic into the regular regular road and high speed roadway.

I've seen quite a few in the US like that, though they are disappearing as more and more roads go to No Stop electronic tag charges and license plate billing.
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garpd
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 6:56 pm

All these junctions seem perfecty safe and easy to me.

Right in my area there is one of the most ill thought out on and off ramp I have ever come across.

Traffic wanting to use the off ramp (orange arrow) have to dodge people crawling onto the motorway from beside and being them (Red Arrow). The section the red arrow is on is a steep climb and folks rarely get up to speed before joining the motorway. It has caused many an accident as slow drivers pull out into fast moving traffic. Or someone who is fast on the On ramp pulls up alongside to a vehicle merging off and BANG.
Now, it strikes me as logical that on OFF ramp should always come before an ON ramp!



Only 300 yards up the same road is the tightest on ramp you'll ever see!
It's a down hill, sharp right hand bend which prone to getting covered in slippy morning dew or icing in winter. It is followed by a sharpish left turn to align with the motorway. The quick direction change has caused many vehicles to spin out there as the g-forces are unloaded and loaded quickly. Consequently many drivers crawl along and do not get up to speed, thus causing motorway traffic to break.

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Luftfahrer
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 7:19 pm

Quoting MD11Engineer (Reply 3):
the kurve forces you to slow down.
Quoting MD11Engineer (Reply 3):
(if you have ever driven for several hours at 120 + km/h, you´ll suddenly find normal roadspeeds like crawling.

There is one Autobahn exit I regularly take which does not have a curve, but goes straight for one or two kilometers. The speed limit goes down to 70 km/h and then to 50 km/h. I really need to watch the speed-indicator more closely then since my perception of speed has definitely changed. It gets back to normal I'm forced to slow down before a curve, though... so they serve a purpose, whether intended or not.  
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Aesma
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RE: German Vs US Highway On-Ramps (RANT)

Sat Mar 05, 2011 8:47 pm

The comparison in the first post is flawed as one is an intersection between a freeway and a town street, it seems. You can get this in France too, and my guess is Germany has the same. Out of the highway/freeway, you get a stoplight. In the cloverleaf design, you don't have to stop, however it may need more merging skills, which is something we learn for our driver's license (mandatory 20h training, and an exam roughly half takers have to pass several times, with more training).

What is really better than this is the stacked system, but that is far more expensive to build (and probably maintain). BTW, is it reasonable to build those in earthquake prone California ?

Quoting Garpd (Reply 42):
Traffic wanting to use the off ramp (orange arrow) have to dodge people crawling onto the motorway from beside and being them (Red Arrow). The section the red arrow is on is a steep climb and folks rarely get up to speed before joining the motorway. It has caused many an accident as slow drivers pull out into fast moving traffic. Or someone who is fast on the On ramp pulls up alongside to a vehicle merging off and BANG.
Now, it strikes me as logical that on OFF ramp should always come before an ON ramp!

There is the same stuff near where I live, and I take it very infrequently when coming back from vacation, several times I didn't understand what was going on until it was too late and I didn't exit as I should have. It's downhill however so the major problem is exiting while people merging are already at full speed.

Quoting Luftfahrer (Reply 43):
There is one Autobahn exit I regularly take which does not have a curve, but goes straight for one or two kilometers. The speed limit goes down to 70 km/h and then to 50 km/h. I really need to watch the speed-indicator more closely then since my perception of speed has definitely changed. It gets back to normal I'm forced to slow down before a curve, though... so they serve a purpose, whether intended or not.

There is this in miniature in my town, with a 110Km/h national road exiting in a straight line for quite an unusual distance, before an almost 90° turn. I would usually continue almost at full speed, coasting until the last moment, until I once saw cops there, stopping people doing like me...
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Zkpilot
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RE: German Vs US Highway On-Ramps (RANT)

Sun Mar 06, 2011 2:40 am

Quoting PanHAM (Reply 21):
Quoting moose135 (Reply 20):
I believe the 8th Air Force helped with that effort in the mid-1940s

no, they rather took charge of the city centres. The old exit/entry ramps at aschaffenburg were still there into the late 90s early 2000s

I think he was making a joke referring to the 'help' they gave to 'removing' them...     
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BMI727
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RE: German Vs US Highway On-Ramps (RANT)

Sun Mar 06, 2011 3:36 am

Quoting travelin man (Reply 31):
Here in SoCal they've been taking OUT the cloverleaf freeway interchanges.

That seems to be the trend around the country. Cloverleafs are pretty space efficient, but the situation where traffic coming in must merge left and traffic leaving must merge right within a short space of a couple hundred feet can slow traffic down at best and be dangerous at worst.

Quoting N1120A (Reply 36):
Meanwhile, the US has ridiculously low speed limits on its highways

That gets really annoying.

But here is my rant: Why can't the US put in more roundabouts? It doesn't take much space, it's efficient since cars don't have to stop in lighter traffic, and there is far less need to be jockeying to get into the correct lane to get where you are going. Of course, when encountering one of the few roundabouts there are here, most American drivers don't seem to have a clue of what to do.
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andz
Posts: 7769
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RE: German Vs US Highway On-Ramps (RANT)

Sun Mar 06, 2011 11:28 am

Quoting BMI727 (Reply 46):
Why can't the US put in more roundabouts?

Like this one?

http://img.photobucket.com/albums/v155/andzz/magicroundabout.jpg
After Monday and Tuesday even the calendar says WTF...
 
PanHAM
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RE: German Vs US Highway On-Ramps (RANT)

Sun Mar 06, 2011 11:55 am

Quoting Zkpilot (Reply 45):
I think he was making a joke referring to the 'help' they gave to 'removing' them...

I understood the joke and had no problems with that, I just forgot the smiley.

.
Was Erlauben Erdogan!!!
 
photopilot
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RE: German Vs US Highway On-Ramps (RANT)

Sun Mar 06, 2011 12:07 pm

Quoting Birdwatching (Thread starter):
WHY, WHY, WHY?? Why would you, as an engineer, EVER use the curvy design when you could just as well use the other one?

Because European cars are designed with HANDLING and CONTROL in mind while the typical USA car is designed to go like stink in a straight line, but handles like sh*t.

Quoting PanHAM (Reply 5):
And it is really fun to drive the tight curves AND we have the cars t do it.

              

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