Could these crazy intersections make us safer?

[Katsmeow]

Here's an interesting challenge: Houston

I actually drive exactly that way whenever I go to my office. The area where 610 approaches I-10 is challenging if you don't want to exit to I-60 as you have to very quickly move to the left to avoid having to exit.

 

[martyp]

Very good point. "They" say we may start to see them in 5 years...

Driverless cars were made legal in California last September.

 

[Ronstar]

I'd love to see roundabouts become a standard as they are in some states/countries, but who knows...

You may in luck. Lots of roundabouts are coming to Illinois, some on state highways. Maybe even a "diverging diamond"

http://67.151.102.46/story/?id=406162

 

[FUEGO]

Anybody ever think all these traffic engineers are just messing with motorists?

 

[ERD50]

Anybody ever think all these traffic engineers are just messing with motorists?

Yes.

Either traffic engineers are extremely incompetent, or maybe no one listens to them.

A couple simple examples. Why do traffic signs with compass points always spell out the word, and often in ALL CAPS? They look like this

EAST
WEST

NORTH
SOUTH

Two letters are identical in East/West, and three in NORTH/SOUTH. It's a waste of space to include letters that don't differentiate.

Why not just a single large

E

W

N

S
?

We lived in a subdivision where they thought it was 'cute' to use a common street name only differentiated by whether it was a 'street' 'avenue', 'court', circle', 'gate', 'terrace' etc. And (you guessed it) the signs looked like this:

JONES st.
JONES ave.
JONES ct.
JONES circle
JONES gate
JONES ter

At night, just try to find the intersection of JONES ct. and JONES st.

And can't traffic lights be 'smart' enough to adapt to the traffic? How many times is there no cross traffic, yet you get the red. Just as some cars approach - they get the red. Everyone stopped for no reason. Or a green arrow when no one is in the turn lane, or a 6 second turn arrow when the turn lane is backed up and blocking the main lane?

And so on.

-ERD50

 

[Ronstar]

Yes.

Either traffic engineers are extremely incompetent, or maybe no one listens to them.

A couple simple examples. Why do traffic signs with compass points always spell out the word, and often in ALL CAPS? They look like this

EAST
WEST

NORTH
SOUTH

Two letters are identical in East/West, and three in NORTH/SOUTH. It's a waste of space to include letters that don't differentiate.

Why not just a single large

E

W

N

S
?

We lived in a subdivision where they thought it was 'cute' to use a common street name only differentiated by whether it was a 'street' 'avenue', 'court', circle', 'gate', 'terrace' etc. And (you guessed it) the signs looked like this:

JONES st.
JONES ave.
JONES ct.
JONES circle
JONES gate
JONES ter

At night, just try to find the intersection of JONES ct. and JONES st.

And can't traffic lights be 'smart' enough to adapt to the traffic? How many times is there no cross traffic, yet you get the red. Just as some cars approach - they get the red. Everyone stopped for no reason. Or a green arrow when no one is in the turn lane, or a 6 second turn arrow when the turn lane is backed up and blocking the main lane?

And so on.

-ERD50

Expect the ALL CAPS signs to be replaced - they're against govt regs.

ALL CAPS? Not OK on road signs, federal government says - USATODAY.com

 

[Htown Harry]

In the traffic engineering business, we have the saying "everyone with a drivers' license thinks they are a traffic engineer".

It's cynical, of course, but is based on the reality that there are extra challenge for those civil engineers who practice in the transportation field. If the OP had posted information on new, efficient and innovative techniques for water distribution, for example, a similar number of us might be affected but there would be crickets for responses.

Heck, good traffic engineering is even a mystery to many in my own field. A BSCE typically requires a single semester of transportation engineering. More than once I been presented a set of plans for a street reconstruction that ignored the challenges drivers might have when running into the "wrong" side of a signalized intersection during the period when traffic is switched to the other side of the street. "Yea, I see what you mean Harry, but the limits of our project are on the south side of the intersection."

Comments so far pointing out the downside of the extra land required for some of these innovative intersection designs are spot on. It's not at all unusual in urban street projects for the costs of land acquisition and the relocation of existing utilities to exceed the actual road construction cost you see on the construction signs.

 

[eytonxav]

Over the past few years, our town replaced two 4 way stop intersections with roundabouts on a road near my neighborhood. I have no data on changes to the accident rates, but these greatly relieved the backups that occurred during morning and afternoon rush hours.

 

[Texas Proud]

In the traffic engineering business, we have the saying "everyone with a drivers' license thinks they are a traffic engineer".

It's cynical, of course, but is based on the reality that there are extra challenge for those civil engineers who practice in the transportation field. If the OP had posted information on new, efficient and innovative techniques for water distribution, for example, a similar number of us might be affected but there would be crickets for responses.

Heck, good traffic engineering is even a mystery to many in my own field. A BSCE typically requires a single semester of transportation engineering. More than once I been presented a set of plans for a street reconstruction that ignored the challenges drivers might have when running into the "wrong" side of a signalized intersection during the period when traffic is switched to the other side of the street. "Yea, I see what you mean Harry, but the limits of our project are on the south side of the intersection."

Comments so far pointing out the downside of the extra land required for some of these innovative intersection designs are spot on. It's not at all unusual in urban street projects for the costs of land acquisition and the relocation of existing utilities to exceed the actual road construction cost you see on the construction signs.

SOOO, you are to blame for all our traffic woes!!! (just kidding)...


The difference between traffic and water is that most everybody will be on that new innovative road, but nobody will be in that newe innovative water distribution system...

IOW, all I want to do is turn on my tap and get water, I really do not care that much on how they get it there... but if I am driving, the design has an impact on ME...

Some of these look interesting, but I do not think would work in a heavy traffic situation... there would be a back up which would block some other part of the intersection... gridlock ensues.... I also see some problems where you are supposed to merge that look like it would be a problem with some of the high traffic areas we have...

On reading one of the articles, I will say that it would look like it would eliminate the T-bone accidents... making it 'safer' in that respect...

 

[Htown Harry]

Some of these look interesting, but I do not think would work in a heavy traffic situation... there would be a back up which would block some other part of the intersection... gridlock ensues.... I also see some problems where you are supposed to merge that look like it would be a problem with some of the high traffic areas we have...

On reading one of the articles, I will say that it would look like it would eliminate the T-bone accidents... making it 'safer' in that respect...

In intersection design, it's all about the left turns.

From a capacity perspective, the most important factor in overall intersection throughput is devoting the greatest possible share of available green light time to the highest-demand lanes of traffic. Those are almost always the through movements. I can move a lot of traffic per minute through the intersection when it's green for three lanes in both the northbound and southbound directions. Conversely, throughput rate goes way down when green time is devoted to single left turn lanes.

Most all of the innovative intersections find a way to make serving the left turn movements less of an interruption on the conflicting through movements.

Safety wise, I believe it's about 45% of all urban crashes that involve one of the vehicles turning left. (Includes both controlled and uncontrolled locations.) If the design can handle those lefts at the intersection in a way where drivers make the movement with fewer potential conflicts, right-angle collisions can go way down.

On the other hand, rear-end collisions at innovative intersections may go up, as unfamiliar drivers jam on the brakes when confronted with a "what the hell do I do now?" wayfinding task.

 

[pb4uski]

Over the past few years, our town replaced two 4 way stop intersections with roundabouts on a road near my neighborhood. I have no data on changes to the accident rates, but these greatly relieved the backups that occurred during morning and afternoon rush hours.

+1 we have a couple state highway intersections that were replaced with rotarys/roundabouts and they are much more efficient at getting traffic through them. Also, it is entertaining watching 18 wheelers go around them.

 

[bUU]

Trucks and rotaries are no laughing matter around here anymore. Back in 2009 a heating oil tanker flipped over at one of the busiest rotaries (in Revere MA) and spilled over 10,000 gallons of oil into a nearby creek. What a mess that was.

 

[ERD50]

In the traffic engineering business, we have the saying "everyone with a drivers' license thinks they are a traffic engineer".

It's cynical, of course, ...

And don't take it personally, it's actually kind of nice that people notice what you do. A little complaining can be better than being totally ignored, heh- heh.

And I don't single out traffic designs, I'm constantly amazed at how many products are so incredibly wonderful in some ways, and have you wondering how could they possibly not have realized how bad or lacking the product is in some other way. The CD and the CD case were a classic example for me (with the case hinges that broke so easily, even for someone like me who handles audio equipment so very gingerly). Like who couldn't figure out that that hinge would break? And they kept making them like that for many years (at least there are more alternate designs now).

But back to traffic, in our area it seems they really neglect to provide a long enough left turn lane on the busy intersections, and some left turn arrows are incredibly short. People really push to get through that green and green/yellow and yellow/red turn arrow, it really does become dangerous. And often, there is a painted median for a couple hundred feet - I have no idea why they don't allow traffic there to lengthen the left turn lane, since they already have the space. Of course people drive on the painted median, making it really dangerous if you follow the law - just when you think it is safe to pull into the lane, a car two lengths behind you roars out and almost hits you.

-ERD50

 

[braumeister]

The most striking traffic engineering story I know involves Brasilia, the capital city of Brazil (the country's former capital was Rio de Janeiro). It was built from scratch, so they could do anything they wanted.

The guy who planned the city (Lucio Costa) was concerned about traffic because his wife had been killed in an accident at an intersection. So he designed the traffic flow to completely eliminate traffic lights and intersections. The idea was to use mainly cloverleafs instead.

As a plan, and as a traffic engineering experiment, it was a disaster.



Transportation in Brasilia

 

[Htown Harry]

And don't take it personally, it's actually kind of nice that people notice what you do. A little complaining can be better than being totally ignored, heh- heh.
-ERD50

Oh, I've gotten some pretty thick skin over the years.

Like most drawn to engineering, I was good with numbers coming up though school. And like most that choose civil engineering, I was drawn toward the idea of big, monumental projects that are right out there for all to see and use.

What they don't prepare you for in school for, however, is the challenges of dealing with the public when you work in a public works agency. Those of us in road building or traffic engineering are often right at the tip of the sword.

Sometimes it works out, though. Today I got a nice thank-you note from an elected official for helping to troubleshoot a sticky situation where a commercial development was coming into an area with big trees and involved HOA's. Funny you should mention left turn lanes - the fight was about how many trees in the median might be saved if we could approve a non-standard design for a left turn lane serving the new shopping center's driveway.

 

[Sarah in SC]

Harry interesting that you mention left hand turns. The article I linked to is about a particular intersection (where I happen to turn left) that has tons of left-turn accidents. That is just they are trying to curb with the proposed "super street" design.
I loved that book, can't remember which, that said there was irrefutable proof that late mergers improved traffic flow. A particular pet peeve of mine!

 

[W2R]

We went through the "Diverting Diamond" in Springfield, Missouri (illustrated in the article). I found it to be utterly terrifying and never want to try it again. I had no idea what to do, but somehow got through it anyway.

However, local residents say that after going through it a few times it is easy, and that it has eased the bottleneck in that intersection. It seems very popular there, and there is a hope that it will be a model for intersections in other communities.