Sorry for the vague thread title (I don't know what to call it) but this short paragraph should explain the question:
In the Tri-Cities of Washington State, there are a number of loop ramps for the freeways (in fact, quite a few A4 parclos compared to the rest of Washington), but a lot of them, over the last decade, have been remodeled to make the loop ramp less of a perfect loop and more of a sharp right off the arterial followed by the normal perfect curve. Any ideas as to why they've done this?
Here's a photo so you don't have to go hunting for your own:
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FBcGz0Gq.png&hash=efa03713d4b90dfc48c40fe2e8d91f671fa7222f)
Traffic calming?
Interesting... maybe they wanted to reduce the ramp speed for that on ramp.
Also, this might sound silly, but perhaps to reduce environmental impact somehow. :-/
Intriguing.
What they did looks like it makes the road more dangerous to drive.
My thought is they want the loop traffic to go slower to avoid people slipping off the ramp, and since it is not coming off a freeway they could do that by making a slow approach to the loop by the sharp turn.
If I had to guess, I'd say it has something to do with pedestrian safety. If you look at the pictures above, the old loops are pretty standard but have no crossing for a pedestrian to get across. The new loops look like they have pedestrian crossings right by the first turn. Making the turn sharper slows the traffic and puts the pedestrian crossing at a more predictable position, making it more likely for drivers to see a pedestrian trying to cross the ramp.
The only flaw I see in my assumption is that the surrounding roadway facilities don't appear to have much pedestrian accommodation. It's hard to say without being able to see a greater context of the surroundings.
The new ramps have painted crosswalks (though they were too cheap to actually put in a sidewalk, even between the loop and the next ramp to connect the crosswalks). The radius reduction makes it a little less likely that drivers will suck a big goose egg at yielding to peds.
Quote from: roadfro on January 29, 2015, 05:22:59 PM
If I had to guess, I'd say it has something to do with pedestrian safety. If you look at the pictures above, the old loops are pretty standard but have no crossing for a pedestrian to get across. The new loops look like they have pedestrian crossings right by the first turn. Making the turn sharper slows the traffic and puts the pedestrian crossing at a more predictable position, making it more likely for drivers to see a pedestrian trying to cross the ramp.
The only flaw I see in my assumption is that the surrounding roadway facilities don't appear to have much pedestrian accommodation. It's hard to say without being able to see a greater context of the surroundings.
Looks like you're correct. I did a bit of looking around on the web, and discovered quite a few federal funds that were given to the local county for pedestrian safety along Rd 68. Since the prior interchange had no pedestrian crossings at all, and the new interchange does, it would appear that the modification was due to pedestrian safety.
But like you said, the pedestrian crossings along the road are, well they're there, but they aren't connected at all. very awkward, but they must be performing the modifications as the monies arrive.
No pedestrian crossing sign either.
https://www.google.com/maps/@46.264829,-119.182151,3a,49.7y,197.51h,87.12t/data=!3m4!1e1!3m2!1sUjSHhZ7Yh69ifSWW1FHd3g!2e0
Quote from: roadfro on January 29, 2015, 05:22:59 PM
If I had to guess, I'd say it has something to do with pedestrian safety. If you look at the pictures above, the old loops are pretty standard but have no crossing for a pedestrian to get across. The new loops look like they have pedestrian crossings right by the first turn. Making the turn sharper slows the traffic and puts the pedestrian crossing at a more predictable position, making it more likely for drivers to see a pedestrian trying to cross the ramp.
The only flaw I see in my assumption is that the surrounding roadway facilities don't appear to have much pedestrian accommodation. It's hard to say without being able to see a greater context of the surroundings.
Sounds likely. It's something I wish they'd do more of around here, with all of Mr. Moses' handiwork in the middle of the damn parks that I walk my dog in.
And I've definitely seen some cases of this loop sharpening, probably for the same reasons, but it does tend to be more typical on exit ramps than entrances. (I-590 at NY 31 is a very recent example, and a much earlier case is on I-490 at NY 31F.)
I would not be surprised if in some places–not necessarily the one shown in this example, mind you–they want to slow large trucks. Seems like some interchanges have had problems with truck accidents on loop ramps.