The "Father of the DDI" Defends Left Hand Exit and Entrance Ramps

[SEWIGuy]

Anyone who is in favor of left-sided ramps probably failed the entire concept of walking to the ride side of the hallway since Kindergarten.

But if I wanted to turn left in Kindergarten, I wouldn't go to the right and "fly over" to head left.   

That being said, I do think that there are times where things get "over engineered" to eliminate left hand exits.  Whether or not the cost of that engineering makes sense is unknown to me.

This thought process immediately shows that people only care about themselves, not the overall flow of traffic.  That's where engineering comes in.

In terms of my example, sure, if you want to take an exaggerated view of things, you're right. 

But, people should keep to the right when walking.  When people stop at their lockers and such, the flow of traffic moves towards the center of the hallway.  But what happens when a few people stop to talk in the middle of the hallway?  Congestion ensues. People have to walk around them, which entails getting close to those already stopped at their lockers.

If you don't want to use a school as an example, think of a supermarket where people stop their carts in the middle.  Or a walking trail, where people stop to talk.  In each case, the ones stopped (just a few) are causing the congestion, and the others have to figure a way around.

To continue on, when you believe things are over engineered, again, you are looking at a very small area, thru horse blinders, without considering the overall impact of traffic flow.  You are also very unaware of all the costs of highway construction.  Why even bother with interchanges? To be cheaper, all roadways should just have intersections.  Traffic lights cost money, so just use stop signs. Wider roadways cost money, so make them one lane each way.  Don't bother with shoulders.  Eliminate signage.  Drainage is a huge cost of roadway building, so just let the roadways and surrounding infrastructure flood.  The base of the roadway goes a foot or more down below the surface.  2 inches of asphalt would definitely reduce the costs.

So the cost to build something is an important part of a project, but it's by far not the only thing.  If it costs $10 million to build something that isn't expected to congest for 20 years, or $1 million to build something that will instantly congest, transportation departments would rather spend the $10 million even though it's more money.

I mean I said I didn't fully understand the engineering involved so...

[Life in Paradise]

In a more suburban area, left lane exits (if put together with merge lanes from both directions) could lessen traffic problems with the intersecting street by having one point of entry/exit with traffic control rather than on each side of the overpass or underpass as the case warranted.

[Occidental Tourist]

Anyone who is in favor of left-sided ramps probably failed the entire concept of walking to the ride side of the hallway since Kindergarten.

This thought process immediately shows that people only care about themselves, not the overall flow of traffic.

You're making a lot of smug assumptions about people's underlying psychological traits based on how they discuss or advocate for a particular roadway configuration.  Has drawing broad-based correlations as to a person's likely behavior based on seemingly unrelated thoughts and opinions served you well in life? Do you see someone eating a burrito at a restaurant and reach valid conclusions about their political leanings, ecological views, or charitable habits?  If I see someone driving a red car, what conclusions should I make about their bathroom hygiene or whether they prefer action movies or dramas?

If you're going to accuse people of being selfish or lacking manners because they disagree with your position about how a roadway should be designed, you may be better served on Twitter than this board.  That sort of jackassery is encouraged there.

[interstatefan990]

Think about the safety aspect. It is much easier to merge left than it is to merge right, with the driver being situated closer to the left-side mirror of the vehicle and therefore able to see and judge other traffic better. Doing away with right-side merge lanes would contribute to at least a noticeable increase in yearly traffic crashes, in my opinion.

And, a quote from Wikipedia's article on Texas' High Five interchange:

It replaces the antiquated three-level, modified cloverleaf interchange built in the 1960s that caused a severe bottleneck by narrowing US 75 down to two lanes at the junction of the two highways. The looped ramps of the cloverleaf forced motorists to slow down drastically, backing up traffic. Left-hand exits contributed to the congestion.

[Scott5114]

But, people should keep to the right when walking.  When people stop at their lockers and such, the flow of traffic moves towards the center of the hallway.  But what happens when a few people stop to talk in the middle of the hallway?  Congestion ensues. People have to walk around them, which entails getting close to those already stopped at their lockers.

Do they actually teach/enforce "keep to the right in hallways" in school in other states? In Oklahoma, it's just a damn mosh pit all the way through high school. And of course, nothing changes when you go to the grocery store or the casino or anywhere else people congregate and there's aisles or other hallway-type spaces, because nobody was ever taught any better. Sigh.

[1995hoo]

That was certainly never taught when I was in school, other than perhaps in my first elementary school when they wanted everyone to stay to the right side going up and down the stairs (that went out the door whenever there was a fire drill, of course).

[US 89]

But, people should keep to the right when walking.  When people stop at their lockers and such, the flow of traffic moves towards the center of the hallway.  But what happens when a few people stop to talk in the middle of the hallway?  Congestion ensues. People have to walk around them, which entails getting close to those already stopped at their lockers.

Do they actually teach/enforce "keep to the right in hallways" in school in other states? In Oklahoma, it's just a damn mosh pit all the way through high school. And of course, nothing changes when you go to the grocery store or the casino or anywhere else people congregate and there's aisles or other hallway-type spaces, because nobody was ever taught any better. Sigh.

I was never taught it explicitly...but it was one of those things that you'd learn pretty quickly. I don't think anything below high school had any rhyme or reason, but when I started high school I learned to keep right in the halls very quickly. If you happened to find yourself on the left side, you'd be constantly bumping into older students who would give you weird looks. Most freshmen would figure it out after a week.

[webny99]

My high school wasn't busy enough for hallway traffic flow to register as a concern, but I tried to keep right when I could, just like I do in any other hallway or aisle or trail or bike path. The concept of KRETP isn't just for roads.

[kphoger]

If I see someone driving a red car, what conclusions should I make about their bathroom hygiene or whether they prefer action movies or dramas?

Action movies.

Also...

[achilles765]

I recognize he's not talking solely about DDIs and is instead talking about left-side ramps in general, but in the DDI context I would argue that left-side ramps in a standard DDI are a different circumstance anyway because the "fast lane" (more properly the "passing lane") is not an issue, as the road with the left-side ramps is, by definition, not going to be a freeway due to there being traffic lights at either end of the DDI where the directions cross over. If there were to be a modified DDI that used grade-separated crossovers to eliminate the two traffic lights, that might be a different scenario.

I didn't click your link (don't have time), but one problem I've noted with left-side ramps in general-purpose lanes (as opposed to managed lanes, which generally carry fewer vehicles) is that it exacerbates the incredibly annoying tendency some people have to camp in the left lane. "I want to exit on the left six miles down the road, so I'm going to get over to the left lane immediately." Ugh.

I can definitely see that being a problem. If you don't give enough advanced noticed, it's confusing. But if you give too much advanced notice, people camp in the left lane. As with all things there's never a one size fits all solution.

I will say that in urban and suburban areas, for instance the Tri-State in Chicagoland, there's so much traffic that all lanes are filled with cars. Yes, the slower traffic generally stays on the right, but it's rare to get an open left lane. In that instance, a left exit with campers wouldn't make things much worse than they already are.

You hit on a very good point about urban areas having so much traffic the left lane isn't really a good fast lane. Here in Houston we don't have very many left exits, just a couple on IH 45 downtown and at IH 10 and IH 69 but there's so much traffic everywhere that a left exit just would not affect traffic in any significant way.
Part of the reason they want to redo 45 is to get rid of the left exits for McKinney street and Allen parkway.

[JoePCool14]

Why even bother with interchanges? To be cheaper, all roadways should just have intersections.  Traffic lights cost money, so just use stop signs. Wider roadways cost money, so make them one lane each way.  Don't bother with shoulders.  Eliminate signage.  Drainage is a huge cost of roadway building, so just let the roadways and surrounding infrastructure flood.  The base of the roadway goes a foot or more down below the surface.  2 inches of asphalt would definitely reduce the costs.

Why even build roads at all? Just drive wherever you want. 

[kernals12]

I recognize he's not talking solely about DDIs and is instead talking about left-side ramps in general, but in the DDI context I would argue that left-side ramps in a standard DDI are a different circumstance anyway because the "fast lane" (more properly the "passing lane") is not an issue, as the road with the left-side ramps is, by definition, not going to be a freeway due to there being traffic lights at either end of the DDI where the directions cross over. If there were to be a modified DDI that used grade-separated crossovers to eliminate the two traffic lights, that might be a different scenario.

I didn't click your link (don't have time), but one problem I've noted with left-side ramps in general-purpose lanes (as opposed to managed lanes, which generally carry fewer vehicles) is that it exacerbates the incredibly annoying tendency some people have to camp in the left lane. "I want to exit on the left six miles down the road, so I'm going to get over to the left lane immediately." Ugh.

I'll trust The Eagles over you thank you very much.

[Scott5114]

I recognize he's not talking solely about DDIs and is instead talking about left-side ramps in general, but in the DDI context I would argue that left-side ramps in a standard DDI are a different circumstance anyway because the "fast lane" (more properly the "passing lane") is not an issue, as the road with the left-side ramps is, by definition, not going to be a freeway due to there being traffic lights at either end of the DDI where the directions cross over. If there were to be a modified DDI that used grade-separated crossovers to eliminate the two traffic lights, that might be a different scenario.

I didn't click your link (don't have time), but one problem I've noted with left-side ramps in general-purpose lanes (as opposed to managed lanes, which generally carry fewer vehicles) is that it exacerbates the incredibly annoying tendency some people have to camp in the left lane. "I want to exit on the left six miles down the road, so I'm going to get over to the left lane immediately." Ugh.

I'll trust The Eagles over you thank you very much.

Are you saying that life in the fast lane surely made you lose your mind?

Cause that'd explain a lot.

[kernals12]

Another one: in Arlington, Virginia, they plan on converting the current US 1 diamond interchange into one with left hand ramps

When I say it saves a lot of space, I'm not kidding

[kernals12]

Looks like Connecticut's love affair with left hand ramps is still strong. They're building a new one on I-91 at the Charter Oak Bridge. It replaces a steep 1 lane right hand exit with a long 2 lane left hand exit.