Tuesday, May 10, 2016

Sometimes, less is better

By Justin Fujioka

Get rid of a lane and traffic flow will improve. You don't hear those words very often. But in the case of the SR 202 roundabout at the eastbound I-90 ramps in North Bend, less is better.

We installed a two-lane roundabout at the interchange in October 2007. While it has allowed traffic to flow more smoothly compared to the original stop-controlled intersection, drivers entering the roundabout from SR 202 in North Bend tend to use the wrong lane within the roundabout and cause confusion for others. To make the roundabout easier to navigate and reduce the risk of collisions, we will be reducing the two-lane roundabout down to one lane along three-fourths of the circle from southbound SR 202 to the eastbound I-90 on-ramp.

SR 202/I-90 roundabout - existing striping

A single-lane roundabout is pretty basic. Slow down as you approach, yield to vehicles already circling before entering, and then drive counterclockwise to your exit. A double-lane roundabout works the same, except drivers must choose a lane as they approach depending on where they are heading, and then yield to two lanes of traffic in the circle before entering.

After the roundabout opened to traffic, we observed a large percentage of drivers making wrong lane choices, especially those entering from southbound SR 202. So we wished to simplify the driver's task. In 2011, we reduced the number of lanes entering the roundabout from that direction from two to one. This lane reduction was our first step in simplifying and scaling back the original two-lane roundabout complexity.

That restriping project improved operations at the roundabout, but still allowed southbound SR 202 drivers the freedom to choose a lane once they entered the circle. In our recent observations, almost 60 percent of drivers are using the wrong lane when exiting the roundabout to the eastbound I-90 on-ramp. The drivers are circulating in the inner (left) lane. Then as they leave the roundabout, cross the path of those in the right circulating lane – a roundabout no-no. Drivers should choose the correct lane upon entering a roundabout and stay committed to that lane until they leave the roundabout.  The observed crossover-error causes driver confusion and increases the potential for collisions.

Many of you have shared your concerns and suggestions about the situation – from colorful pavement markings to added signage for those who don't use this roundabout regularly. In the end, we decided getting rid of a lane within the circle would help clear up confusion for all drivers. Just like the last time we removed a lane here, our recent vehicle counts and traffic analysis for future volumes show one lane will be able to handle traffic at the interchange without added congestion.

SR 202/I-90 roundabout - new striping

Work on this low-cost project is scheduled to take place from 9 a.m. to 3 p.m. Wednesday, May 11. Drivers can expect single-lane and shoulder closures within the roundabout, with minimal delays. The new striping will use thermoplastic pavement markings, a much longer lasting and durable pavement marking material than paint.

Also proven – roundabouts reduce collisions and provide a safer way for pedestrians and bicyclists to navigate traffic. And that's why we've been adding more and more of them and some of you may have even noticed them popping up all across the country. In this case, more is better.

9 comments:

jakeroot said...

If the roundabout is incapable of handling future traffic levels, will the roundabout be converted back into a dual left turn (when, and if, traffic levels exceeds current capacity)?

Edward said...

I think this is a great idea, I use this roundabout on a daily basis and see near misses almost daily.

Monica said...

I have disliked this roundabout for ages! Coming from North Bend, turning 'left' onto I-90 Eastbound, where do you select the proper lane? In the roundabout!! Ack!! This sounds like a great solution, thank you!

desviz said...

Do you know who did the visualization graphic? Does WSDOT do those sort of things? Nice job...

Tom Barr said...

It is sad that we dumb down a working traffic circle and restricting it to a single lane to accommodate low skill drivers.

The continuous stream from 202 SB will cause a backup on the off ramp again with this single lane in the circle.

I am sorry but if drivers are confused that they need to be in the right lane to exit to the right of the circle in order to get on I90 EB they need their licenses revoked. This is basic common sense.

WSDOT said...

Our data shows that one lane will be able to handle capacity at this roundabout. Our engineers will be taking new data this summer though to see if traffic patterns change and we are open to future changes at the circle.

And thanks for the kudos on the graphics. WSDOT does have in-house graphic designers that often assist in making construction plans much more visually appealing.

Jeff Gray said...

"Get rid of a lane and traffic flow will improve. You don't hear those words very often."

Sure didn't work on 405N after you stole a lane while ramming the Extortion Toll Lanes down our throats. Hit ten bucks again today...you know, that magical threshold we would only "rarely" see which is now a daily occurrence? Everything W$DOT does is an utter failure.

Can't wait for the upcoming election cycle...going to be sending Inslee, Clibborn and Liias packing. Also, looking forward to Patty Rubstello getting fired.

Vince R said...

"Our data shows that one lane will be able to handle capacity at this roundabout. Our engineers will be taking new data this summer though to see if traffic patterns change and we are open to future changes at the circle."

Hopefully they are not the same engineers that estimated the 'improvements' we have yet to see from GTG.

In general the roundabouts seem to be improving traffic in the areas I have used them. However, there are way too many people that do not seem to understand the way they should work.

Today, A single driver stopped at the roundabout, instead of yeilding. They waited until the circle was empty before proceeding. This was about 3 minutes. Meanwhile, the traffic behind him backed up about 2 dozen cars.

Monday, I was almost in a serious accident by Fall City when a gravel truck didn't think to even slow down approaching the round about... and lucking, at the last minute was able to lock up their brakes and miss my car by inches. In several areas, the larger trucks do not really yield to vehicles in the circle and have just blasted on through.

Last Thursday by Carnation, I saw a truck take out an SUV by not yielding. Fortunately, the lady driving was not injured and they were able to pull the vehicles off the road.

Stephen Matlock said...

If you are used to the old system, it's a change that has to be accommodated.

If you're new to this intersection, it's not hard to figure out.

Stay in the left lane to get to North Bend.

Stay in the right lane to get to the apartments/condos on the right.

Maybe what has to happen is a physical barrier between the left and right lanes so that people who stay to the right can't stop and try to get into the left lane.