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Cichlidae
Aug 12, 2005

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Dr. Infant, MD

DaisyDanger posted:

Even though I'm not a traffic engineer, I think I could see a few problems with this. Say the light is saying there are 3 seconds left on a green or yellow light. This would cause a more reckless driver to gun it and try to make it through the intersection. This could also cause some people to preemptively start moving before a red light fully ended.

I'm not sure about NZ, but in the US, the time a light stays green is not always set in stone either.

Bingo, good job! You get a gold star for the day.

nm posted:

The problem, or at leats one of the problems, as I theorize (in a very non-expert way) is the merges into 99 S (worth noting that under that first bridge is a bridge abutment, not a shoulder). At least that's where my parents were almost killed. But that interchange is always on top 10 lists and is perpertually covered in broken car parts.


Yep, this is why we need good shoulders. Zooming in, the pavement looks to be in incredibly bad shape. Additionally, due to the close-by interchanges, there are weaving sections on the eastbound, westbound, and northbound legs heading away from the interchange.

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Cichlidae
Aug 12, 2005

ME LOVE
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Dr. Infant, MD

MyFaceBeHi posted:

We have these ramp signals in the UK too and I agree that they are dumb. There is a notorious section of motorway near me that has this and it does the same thing during peak hours where it will let about 4 cars on regardless of how much traffic is on the road. The worse thing is they have appeared along any stretch of Motorway that is near any major town or city, so you can't avoid them either.

You'd better get used to them, because they're going in all over the world. Japan's poised to put them on every single on-ramp. They may inconvenience you for a few minutes, but they've been proven to reduce delays overall by raising the speed and capacity of the freeway, and reduce accidents by a quarter. I know stopping for 10 seconds feels a lot longer than driving an extra 30 seconds because everyone's going slower, but we've got to look at the big picture when we design such extensive systems.

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

ItchyDroopy posted:

Good stuff. Seems like a really fun job.


Can you tell us a bit more about the Cheshire 84 fiasco and highway construction in general? i.e. Do contractors pretty much have free will as they wish with the project? Im sure they have a contract... but it makes me wonder if they can put in non functional catch basins, what is preventing them from using sub par materials in construction?

I can't tell you too many details about that project, since the litigation is still fresh and I might get in trouble. However, I can tell you that they certainly cannot put in non-functional equipment in general. What they did was against the contract's specifications, and both the contractor and the inspector who missed the glaringly obvious mistake were taken off the job. Our specifications are massive in order to prevent the kind of cost-cutting loophole that any contractor would gladly use. The materials section is its own book, and it has very detailed tests that must be done on every bit of material that's used in the project. If the contractor wants an exception, the engineer has to approve it first.

quote:

Also HOV lanes, which mostly get blocked by buses and slow cabbies... why not convert them to 2 additional regular lanes?

The average vehicle in the USA carries 1.1 people. That's not very efficient; we'd rather have people carpool or take mass transit. The HOV lane isn't there to add capacity, it's there to provide an incentive. When you're sitting in heavy traffic and see buses and carpools whizzing past at relatively high speeds, hopefully you're thinking about changing the way you get to work.

In some cases, the HOV lane can add a lot of extra capacity, though. If the average car using an HOV lane carries 3 people, then one HOV lane can carry as many people as 3 regular lanes. In practice, I'd rather have the extra lanes in some places, but it's hard to argue against encouraging mass transit.

quote:

Why/Who in their right mind thought it was OK to have all major highways in CT run right smack through major cities and intersect in hartford?

Well, as shown in that map I posted earlier, Hartford was supposed to have 2 or 3 beltways around it. People driving through the state could have used them, and I-84 and I-91 were designed with that in mind. We built 84 and 91 before the beltways, because they were needed the most, but then all the beltways (completed I-291, I-491, I-284, I-484, completed I-691, completed CT 10 expressway, completed CT 20 expressway, CT 140 expressway, and completed CT 190 expressway, to name a few) got canceled thanks to NIMBY and environmental issues. Again, the problem isn't what got built, it's what didn't get built.

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

smackfu posted:

The worst is on I-91 North of Hartford where there is basically an unused lane between the HOV and the regular lanes. Efficient use of land there.

Those HOV dividers aren't even fit to carry traffic. If we let trucks pass over them, the pavement would fail rather quickly. Like I said, though, one HOV lane in the right conditions can carry as much as several general purpose lanes. Even if we did put in more lanes up there, it wouldn't change things significantly, because I-91 is so bottlenecked going through Hartford.

I'd say the main problem with Connecticut's HOV lanes is that they're not extensive enough, and the weave problems they create in Hartford and Windsor Locks.

Kemian
Jul 26, 2004

Economics is not a science, and never will be!

Here's a question I've wondered about for a while: Why is the speed limit on I-84 50-55 between Waterbury and Hartford? It seems like people still go 65-70, but what's the thinking behind having that stretch be so much lower than most of the other highways that go through non-city areas?

Funktor
May 17, 2009

Burnin' down the disco floor...
Fear the wrath of the mighty FUNKTOR!
A few questions. A bit Michigan-centric since I used to live there.

1. Michigan Lefts. They seem to work pretty well to me. What's your take?

2. I'm interested in highway numbering. Do the US and State highways following any numbering conventions like the interstates? Also, why the heck is I-96 an interstate at all? As far as I can tell it exists solely in Michigan. Does that happen anywhere else?

3. The interchange at I-96 and M-39 (Southfield Freeway) outside Detroit is about the only place I can think of where you have four roads above one another. A sight to behold. Is this one of those "Stacks" you were talking about or it it something else?

PyRosflam
Aug 11, 2007
The good, The bad, Im the one with the gun.
Someone asked earler about min yellow times, I understand that you dont want drivers to know how long a yellow will last but at the same time there needs to be some min amount of time for a given type of road. This comes up quite a bit when red light cams go up and then its found out that the town got someone to lower the light timer much lower then the road was built for.

My question is, is there a hard and fast rule that the yellow needs to be at least X long (based on how many lanes hit the intersection and the speed limit for the area)

InterceptorV8
Mar 9, 2004

Loaded up and trucking.We gonna do what they say cant be done.

Billy Maize posted:

I like roundabouts way more than 4 way stops but nobody knows how to use either one.

For some reason, the city where I grew up decided to use roundabouts as a freeway exit.

http://maps.google.com/maps?f=q&sou...013937&t=h&z=17

As a OTR driver, and since that's RIGHT next to the Flying J, I can truly say that one sucks. They never make the road wide enough to account for trailer offtracking, and if you are all the way out to the DOT with your tandems, the poo poo in the middle of that roundabout is gonna have a visit from Mr. Trailer Tires.

It doesn't help that people dart out in front of you, and if you think that's bad with a car, just think of taking 40 tonnes of a 75 foot long tractor trailer through that poo poo.

Neutrino
Mar 8, 2006

Fallen Rib
Michigan Lefts are a way to reduce accident severity at intersections. They do this by removing left turns at high speed intersections. Accidents from left turn movements can be one of the most severe of any types of accidents so wherever you can, you want to avoid them. I think they are a great idea and as long as you have the real estate, they should be put in place.

quote:

As a OTR driver, and since that's RIGHT next to the Flying J, I can truly say that one sucks. They never make the road wide enough to account for trailer offtracking, and if you are all the way out to the DOT with your tandems, the poo poo in the middle of that roundabout is gonna have a visit from Mr. Trailer Tires.

That's what the apron around the center circle is typically designed to do. Drive over them to your heart's content.

Neutrino fucked around with this message at 20:46 on Jul 31, 2009

InterceptorV8
Mar 9, 2004

Loaded up and trucking.We gonna do what they say cant be done.

Neutrino posted:

Michigan Lefts are a way to reduce accident severity at intersections. They do this by removing left turns at high speed intersections. Accidents from left turn movements can be one of the most severe of any types of accidents so wherever you can, you want to avoid them. I think they are a great idea and as long as you have the real estate, they should be put in place.


That's what the apron around the center circle is typically designed to do. Drive over them to your heart's content.

Yeah, I know that, sometimes though they, the builders, put a big enough lip on the apron that it comes close to being a curb, and drat it, I don't want to bend the lip of my wheel.

There is one in Fernly NV that has pretty good lips on it that if I was out to the DOT bumper, I'd be hitting poo poo.

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

Kemian posted:

Here's a question I've wondered about for a while: Why is the speed limit on I-84 50-55 between Waterbury and Hartford? It seems like people still go 65-70, but what's the thinking behind having that stretch be so much lower than most of the other highways that go through non-city areas?

You can blame West Hartford for that. I-84, as another poster noted, had substandard shoulders along that stretch, and too few lanes through West Hartford and Farmington. These factors resulted in a lower speed limit. Although the shoulder problem has been fixed from Waterbury to Southington, West Hartford absolutely refuses to allow widening in their town. I don't think the State Traffic Commission would want to raise speed limits piecemeal, so bumping it up to 65 in that area depends on West Hartford taking their heads out of their collective arse.

And some :siren:super speed limit gossip:siren:! I may or may not have seen a proposal to lower the speed limit on I-95 by extending the 50 mph area near New London. Ouch!

Cichlidae
Aug 12, 2005

ME LOVE
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Dr. Infant, MD

Funktor posted:

A few questions. A bit Michigan-centric since I used to live there.

1. Michigan Lefts. They seem to work pretty well to me. What's your take?

I am a big fan of them, despite my UPer boss having no idea what they are. Like a jughandle, it's a great way to take care of left turns while removing a phase and improving operation. There have been plenty of studies done that prove their worth. Unfortunately, it's a bit confusing to unfamiliar motorists, so we won't see them in my state for some time.

quote:

2. I'm interested in highway numbering. Do the US and State highways following any numbering conventions like the interstates? Also, why the heck is I-96 an interstate at all? As far as I can tell it exists solely in Michigan. Does that happen anywhere else?

Before the 1920s, routes weren't often numbered. In 1922, New England decided to number a few dozen major roads, calling them New England interstate routes. The odd-numbered routes went east-west, and the even-numbered routes went north-south.

The feds said, "wait, what? We want in on this!" in about 1930 and developed the federal route system that still stands today. Unfortunately for New England, they decided that odd-numbered routes would go north-south, and vice versa for the others. Well, poo poo! New England had to renumber all of its roads, though some still maintain the tradition, like 8, 12, and 32, which all run north-south. The federal routes, by the way, started with low numbers in the northeast and worked to high numbers in the southwest. Every multiple of 10 is a "major" east-west route, with 2 getting an honorary distinction as major, as they didn't want a US 0. Triple digit US routes, like 202, are bypasses or spurs of their respective two-digit routes.

Now when the Interstate Highways were planned in the 40s and 50s, they decided to use the same numbering convention. Problem was, people would get confused if US 6 and I-6 were right next to each other. Therefore, they started numbering in the southwest, and worked their way up to the northeast. Interstates don't actually have to go between states, and several don't, though federal routes that don't cross state lines are slowly being phased out.

State highways, of course, depend on the state. CT follows the national odd-N/S even-E/W convention for the most part, and doesn't allow interstate/federal/state routes to share a number. Each time an interstate was created here, a state route had to have its number changed. Massachusetts, on the other hand, has some interesting hosed-uppedness, such as Route 3, which is a US route west of Boston and a state route east of it.

quote:

3. The interchange at I-96 and M-39 (Southfield Freeway) outside Detroit is about the only place I can think of where you have four roads above one another. A sight to behold. Is this one of those "Stacks" you were talking about or it it something else?

Yep, that's a stack. Those aren't too rare, which makes sense considering they're the highest capacity interchange. They're all over urban areas in many countries. Have a look around Google Earth for fun!

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

PyRosflam posted:

Someone asked earler about min yellow times, I understand that you dont want drivers to know how long a yellow will last but at the same time there needs to be some min amount of time for a given type of road. This comes up quite a bit when red light cams go up and then its found out that the town got someone to lower the light timer much lower then the road was built for.

My question is, is there a hard and fast rule that the yellow needs to be at least X long (based on how many lanes hit the intersection and the speed limit for the area)

Well, like I said, England has all yellow times 3 seconds. We won't allow anything lower than 3 seconds here, even if it's warranted, and generally nothing above 5 seconds. The only time it's longer is when it's not an actual "yellow light," but a flashing "don't walk" in a pedestrian phase, which is coded as a yellow.

As for the equation itself, it only has one variable: approach speed. The other factors, reaction time and braking acceleration, are considered to be constants. If you want to get really nitpicky, though, the approach grade counts, though it's negligable in most cases.

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

InterceptorV8 posted:

As a OTR driver, and since that's RIGHT next to the Flying J, I can truly say that one sucks. They never make the road wide enough to account for trailer offtracking, and if you are all the way out to the DOT with your tandems, the poo poo in the middle of that roundabout is gonna have a visit from Mr. Trailer Tires.

It doesn't help that people dart out in front of you, and if you think that's bad with a car, just think of taking 40 tonnes of a 75 foot long tractor trailer through that poo poo.

We design our roundabouts here with flush truck aprons around the island in the center and in the "webs" between the approaches, just for you. We use patterned stamped concrete, so it looks like bricks, but it's over a foot thick and can support trucks easily. All the same, watching you guys drive around them, I was amazed to see that there's mostly no tracking at all! Seriously, truck drivers have some impressive turning skills. The only person I saw drive on it was, you guessed it, an elderly woman who had no idea what was going on. "Huh? Why's there brick in the middle of the road? Let me go run over some more orphans and girl scouts."

Edit: For those who aren't familiar with truck aprons, they're the red thing in this picture. They're made for trucks to drive over, but to discourage cars.

Cichlidae fucked around with this message at 22:10 on Jul 31, 2009

Cichlidae
Aug 12, 2005

ME LOVE
MAKE RED LIGHT


Dr. Infant, MD

Neutrino posted:

Michigan Lefts are a way to reduce accident severity at intersections. They do this by removing left turns at high speed intersections. Accidents from left turn movements can be one of the most severe of any types of accidents so wherever you can, you want to avoid them. I think they are a great idea and as long as you have the real estate, they should be put in place.


That's what the apron around the center circle is typically designed to do. Drive over them to your heart's content.

This guy knows what he's talking about :) Are you a traffic engineer, too, or just a roadgeek?

Tambreet
Nov 28, 2006

Ninja Platypus
Muldoon

Cichlidae posted:

Triple digit US routes, like 202, are bypasses or spurs of their respective two-digit routes.

I've also read that for the triple-digits, if the first number is even, it will connect back up with the original route (bypass), and odd first digits are spurs. I'm not sure if this is always the case, but it is for every road I can think of around here.

And the even/odd numbering can be very confusing in places like Chicago, where the major East-West expressways 90 and 94 both run North-South. I still don't understand whey they don't label them N/S on the signs around here (or both E/W and N/S).

cerror
Feb 11, 2008

I have a bad feeling about this...
This question may have more to do with driver psychology than road design, but I'll ask anyway. I drive the Palmer-Wasilla Highway on a regular basis. It's mostly straight with a few shallow curves around hills and such. Near town on either end of it the speed limit is 45, which makes sense to due all the traffic entering and exiting the road. However, for most of the length the speed limit is 55. Now we get to that differential problem you mentioned way back. For some bizarre reason, at least 50% of the traffic on will only drive 40 to 45. This makes life extremely frustrating for the rest of us who are paying attention to signs. And it only happens on this road! All the other major ones seem fine. So, is this sort of going-too-slow issue a problem in other areas that are moderately suburban? Or, are Alaskans just morons who don't pay attention to signs?

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

Undeclared Eggplant posted:

I've also read that for the triple-digits, if the first number is even, it will connect back up with the original route (bypass), and odd first digits are spurs. I'm not sure if this is always the case, but it is for every road I can think of around here.

That's half true. Even first digit means it ends at another interstate, not necessarily the same one at which it began. Of course, there are exceptions due to changed plans and weird coincidences:

I-238 in California - there is no I-38. Its parent is actually I-80, which ran out of numbers for its children.
I-395 starts and ends at an interstate, yet has an even first digit.
I-195 and I-495 are coterminous.

quote:

And the even/odd numbering can be very confusing in places like Chicago, where the major East-West expressways 90 and 94 both run North-South. I still don't understand whey they don't label them N/S on the signs around here (or both E/W and N/S).

That's why we get wrong-way concurrencies. As I mentioned before, it's possible to be driving on RI 114 both North and South at the same time.

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

comaerror posted:

This question may have more to do with driver psychology than road design, but I'll ask anyway. I drive the Palmer-Wasilla Highway on a regular basis. It's mostly straight with a few shallow curves around hills and such. Near town on either end of it the speed limit is 45, which makes sense to due all the traffic entering and exiting the road. However, for most of the length the speed limit is 55. Now we get to that differential problem you mentioned way back. For some bizarre reason, at least 50% of the traffic on will only drive 40 to 45. This makes life extremely frustrating for the rest of us who are paying attention to signs. And it only happens on this road! All the other major ones seem fine. So, is this sort of going-too-slow issue a problem in other areas that are moderately suburban? Or, are Alaskans just morons who don't pay attention to signs?

I see behavior like that when a speed limit abruptly changes to a higher value. Have you noticed that, when the limit drops by a significant margin, we put up big yellow signs that say "REDUCE SPEED AHEAD" and the like? Well, there's no equivalent for raising the limit. I'd say that most motorists just legitimately don't notice it. Do you pay attention to every single speed limit sign you see, or just the first one on the road?

Of course, people could just be trying to save gas. I read about hypermilers today, and those guys are nuts! Tailgating semitrailers, running through stop signs and red lights, driving extra slow to save fuel... it only takes a few of them to make it seem like everyone's going 10 below.

Cichlidae fucked around with this message at 22:29 on Jul 31, 2009

cerror
Feb 11, 2008

I have a bad feeling about this...

Cichlidae posted:

I see behavior like that when a speed limit abruptly changes to a higher value. Have you noticed that, when the limit drops by a significant margin, we put up big yellow signs that say "REDUCE SPEED AHEAD" and the like? Well, there's no equivalent for raising the limit. I'd say that most motorists just legitimately don't notice it. Do you pay attention to every single speed limit sign you see, or just the first one on the road?

I'm a paranoid driver, so I try to pay attention. But yea, I suppose the innocuous white signs are easy to miss. Maybe they should outline them with another color to make them stand out more. :crossarms:

cerror
Feb 11, 2008

I have a bad feeling about this...

Cichlidae posted:

Of course, people could just be trying to save gas. I read about hypermilers today, and those guys are nuts! Tailgating semitrailers, running through stop signs and red lights, driving extra slow to save fuel... it only takes a few of them to make it seem like everyone's going 10 below.

Most of these people are driving trucks and SUVs. I think they're just dumb.

adaz
Mar 7, 2009

Do you get to design bike trails (or rail trails) at all, or is that something handled by a private company?

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

adaz posted:

Do you get to design bike trails (or rail trails) at all, or is that something handled by a private company?

I design those, yes. They're generally 10 feet wide with two lanes, and the MUTCD has a special section dedicated just to them. Bike paths are super easy to make, since the speeds and loads are so low relative to what the tracks are designed for (trains).

nbakyfan
Dec 19, 2005
I switched to Civil Engineer to become a traffic engineer, but I just switched back to ME so I can go to medical school. (Its hard to know what you want to do at 18/19 :(). But anyways, one thing that drives me up the wall is the I64-WB and 264 interchange. In the morning this will be backed up for a mile because people fail to realize that the left portion of the branch going to 264 is for 264 south bound and the right sector is for 264 north bound. So then you have people who are in the right lane trying to get over to the left lane when they see thats 264-S. Why don't they just put up a clearer and direct sign then the one in use? I'm sure some one else besides me has noticed this.




Also, I was doing an environmental survey for a major interstate in New York to connect to another population center in New York (not sure if this is public or not), and I was just wondering how often you run across major changes to plans because of wildlife. I never would have thought an interstates placement would be based around animal life.

nbakyfan fucked around with this message at 00:28 on Aug 1, 2009

ziyaarah
Jul 26, 2009

by Peatpot
GREAT THREAD. I love this kind of stuff. OP, or anyone who wants to take a stab at it: If you could completely redesign New York City's freeway system, how would you do it? Keeping in mind you must leave the grid-system of streets and avenues intact. You can change the West Side Highway, FDR, Long Island Expressway, and others, however.

nm
Jan 28, 2008

"I saw Minos the Space Judge holding a golden sceptre and passing sentence upon the Martians. There he presided, and around him the noble Space Prosecutors sought the firm justice of space law."

Cichlidae posted:

I design those, yes. They're generally 10 feet wide with two lanes, and the MUTCD has a special section dedicated just to them. Bike paths are super easy to make, since the speeds and loads are so low relative to what the tracks are designed for (trains).
Sweet, now I can bitch about more.

Bike paths that parallel roads with frequent crossings.
Do people not see how dangerious this poo poo is?

Here's one example that is by far not the worst
http://maps.google.com/maps?client=...002639&t=h&z=19

I also hate bicycle lanes. Who thought that was a better idea than a wider lane?


This is still a loving awesome thread, thanks!

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

nbakyfan posted:

I switched to Civil Engineer to become a traffic engineer, but I just switched back to ME so I can go to medical school. (Its hard to know what you want to do at 18/19 :(). But anyways, one thing that drives me up the wall is the I64-WB and 264 interchange. In the morning this will be backed up for a mile because people fail to realize that the left portion of the branch going to 264 is for 264 south bound and the right sector is for 264 north bound. So then you have people who are in the right lane trying to get over to the left lane when they see thats 264-S. Why don't they just put up a clearer and direct sign then the one in use? I'm sure some one else besides me has noticed this.




I'm sure they're waiting for the new MUTCD to come out. See how some of the arrows point up and some point down? There's an ongoing debate as to which method is superior, and hopefully it'll be fixed in a couple years. I would personally put up an overhead sign at 2 miles, 1 mile, and 1/2 mile showing the three lanes splitting so that motorists would know exactly how the interchange looks and have plenty of time to change lanes.

quote:

Also, I was doing an environmental survey for a major interstate in New York to connect to another population center in New York (not sure if this is public or not), and I was just wondering how often you run across major changes to plans because of wildlife. I never would have thought an interstates placement would be based around animal life.

It happens all the time! Even building a 1-mile stretch of US 7 that had been surveyed extensively, construction was halted midway through because of some salamanders or something. Lots of protected species only come out at one time of the year, so it's nearly impossible to find them all with just one survey. All it takes is a couple of box turtles to force a realignment and the millions of dollars of change orders that go with it.

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

ziyaarah posted:

GREAT THREAD. I love this kind of stuff. OP, or anyone who wants to take a stab at it: If you could completely redesign New York City's freeway system, how would you do it? Keeping in mind you must leave the grid-system of streets and avenues intact. You can change the West Side Highway, FDR, Long Island Expressway, and others, however.

Other than bringing the freeways up to spec (cough cough Pulaski Skyway), I wouldn't change too much. Yes, there's craploads of congestion, but New York has massive amounts of mass transit, and very few city-dwellers actually need cars. I'd love to bury the freeways in more tunnels, but I don't think the geotechnical situation there is great, and I'm sure the Department of Homeland Security wouldn't like the idea.

What the heck, though. If we're assuming everyone has cars and wants to drive on freeways, let's take care of that. Just the Manhattan area, though; I don't have all day. I don't know all that much about NYC, despite living so nearby.



Assumptions: All the bridges and tunnels are gone, land values are higher where buildings are taller, NYC won the Powerball a few thousand times, and the freeways have excellently designed interchanges.

adaz
Mar 7, 2009

Cichlidae posted:

I design those, yes. They're generally 10 feet wide with two lanes, and the MUTCD has a special section dedicated just to them. Bike paths are super easy to make, since the speeds and loads are so low relative to what the tracks are designed for (trains).

How long are they designed to last? Just curious, the trails out by me are all concrete so I assume they will last, essentially, for forever.

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

adaz posted:

How long are they designed to last? Just curious, the trails out by me are all concrete so I assume they will last, essentially, for forever.

For trails like that, traffic is no longer the determining factor for age; weather is the main factor. In a warm, dry climate, yeah, it could last more or less forever. Around here, where it's wet and there are a lot of freeze/that cycles, it'll last about as long as your sidewalk unless the subgrade is in really good shape.

Socket Ryanist
Aug 30, 2004

Behold, the 360-degree freeway onramp!

http://maps.google.com/maps?q=san+f....00284&t=h&z=19

(with a parking lot in the middle of it of course)

ItchyDroopy
May 24, 2008

Kemian posted:

Here's a question I've wondered about for a while: Why is the speed limit on I-84 50-55 between Waterbury and Hartford? It seems like people still go 65-70, but what's the thinking behind having that stretch be so much lower than most of the other highways that go through non-city areas?

Actually 691 to Waterbury has a 45 limit... eeek


Cichlidae, thanks for your explanation... good stuff!

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

Socket Ryanist posted:

Behold, the 360-degree freeway onramp!

http://maps.google.com/maps?q=san+f....00284&t=h&z=19

(with a parking lot in the middle of it of course)

Yep, the loop is necessary to gain the elevation to get to the second deck of the freeway! That particular ramp is even in the Green Book, I believe, or one just like it.

Neutrino
Mar 8, 2006

Fallen Rib

Cichlidae posted:

This guy knows what he's talking about :) Are you a traffic engineer, too, or just a roadgeek?

Please, Traffic Engineer? No, I'm a Highway Design Engineer. Tut.

smackfu
Jun 7, 2004

ItchyDroopy posted:

Actually 691 to Waterbury has a 45 limit... eeek
That doesn't sound right.

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

smackfu posted:

That doesn't sound right.
I can check it on Monday when I'm back in the office. We have a nice set of books called Straight Line Diagrams that have every mile of every state route, showing intersecting roads, maximum safe speeds, speed limits, grades, 85th percentile speeds, you name it...

Socket Ryanist
Aug 30, 2004

Cichlidae posted:

Yep, the loop is necessary to gain the elevation to get to the second deck of the freeway!
The freeway only has one deck though?

smackfu
Jun 7, 2004

Cichlidae posted:

I can check it on Monday when I'm back in the office.
Unless he meant the ramp only?

Cichlidae
Aug 12, 2005

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Dr. Infant, MD

Socket Ryanist posted:

The freeway only has one deck though?

Yeah, sorry, typing faster than I can think :) I didn't mean that it had two decks; it's a viaduct, and the deck is above the street, hence the upper deck. Not second.

Neutrino posted:

Please, Traffic Engineer? No, I'm a Highway Design Engineer. Tut.

Ah yes! We're busy playing with our French curves and doing wishy-washy guesswork while you guys do the real math. You wouldn't believe how many of my coworkers can't do basic trigonometry, even though we all went to engineering school. Maybe in a few years I'll move downstairs to Highways and see what it's like there.

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Cichlidae
Aug 12, 2005

ME LOVE
MAKE RED LIGHT


Dr. Infant, MD
We've got a bit of free time, so here's a quick rundown of the agencies in the USA most responsible for transportation-related policy.

FEDS
- Secretary of Transportation: Oversees federal transportation agencies and resolves high-level disputes.
- Federal Highway Administration (FHWA): Responsible for road transportation across the country, supervises projects on the National Highway system.
- Federal Railroad Administration (FRA): Rails roads.
- Federal Aviation Administration (FAA): Flies around in planes wishing they were the FHWA.
- National Highway Traffic Safety Administration (NHTSA): Makes sure you're wearing your seatbelt.

NGO
- American Association of State Highway and Transportation Officials (AASHTO): Writes policy books and sells them for enormous fees. Used to be called AASHO. Hahaha, rear end ho...
- Institute of Transportation Engineers (ITE): Writes incredibly dense and buzzword-filled books on Intelligent Transportation Systems.
- American Society of Civil Engineers (ASCE): YOU CAN'T CUT BACK ON FUNDING! YOU WILL REGRET THIS!!!

BOOKS
- Manual for Uniform Traffic Control Devices (MUTCD): Free book from the FHWA, lacking page numbers. Tells you everything you need to know about signals, signing, pavement markings, etc.
- A Policy on the Geometric Design of Highways and Streets (Green Book): $250 paperback from AASHTO explaining how to design road geometrics of all sorts.
- A Manual of User Benefit Analysis for Highways (Red Book): $120 book from AASHTO that explains the basics of engineering economics.
- Roadside Design Guide: $160 book from AASHTO that explains why we use guardrail.
- Necronomicon: Pray to the Dark Lord that AASHTO doesn't raise prices again.

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