I got an awesome email from WSDOT today.
The intersection of the northbound I-405 exit 9 ramp and Lake Washington Blvd is frustrating to navigate while on the bus due to the westbound traffic not needing to stop. Who should I contact to to request the intersection become a 4-way stop (or better, a roundabout)?King County referred me to WSDOT, so I queried them. WSDOT then said I needed to talk to King County. I replied that I'd already done that and WSDOT roughly said, "Oh. Sorry. We'll look into this."
The above back and forth was spread between October and late March. Today I got this:
Mr. Lombardo,
First of all, my apologies for the time it has taken me to respond to this inquiry; it arrived on my desk a little out of order. Ideally I would have had a chance to review the earlier e-mail prior to its going out.
In response to your inquiry, we looked at the current operations of the intersection, and analyzed the location for three options; all way stop control, signal, and roundabout. We also looked at the accident history, which turns out to be minor - two rear end accidents in the past three years, both associated with the right turn onto the northbound ramp.
Our observation of the current operations is that overall, the intersection operates well. On the day that we choose to train our cameras on the ramp, we noted no discernible ramp queuing - that's not to say that it doesn't happen, but on the day we watched it didn't. We also talked with our freeway operations center - they monitor traffic on a daily basis, and they are not aware of a significant queuing problem at this ramp either.
In order to install a signal or all way stop control, there are certain traffic volume thresholds that need to be met, per national guidelines contained in the Manual on Uniform Traffic Control Devices (MUTCD). We looked at the volumes for the intersection, and they are not high enough to warrant installation of either a signal or all way stop control. We also ran some traffic simulation models just to verify, if all way stop control volumes were met, what the impact on the operations of the overall intersection would be. Not good - the westbound movement in the morning, primarily right turning traffic onto the northbound on-ramp, would degrade to what we term Level of Service (LOS) F, with queues of almost a thousand feet and average vehicle delay of almost eight minutes. Since there is no restriction on this movement currently, the impact is significant.
We also looked at the operations for a roundabout, and as suspected, it would operate well. However, it is not a viable option due to the very high cost associated with it, and the lack of significant benefit, either capacity or safety.
Overall, the intersection operates well based on all of the criteria that we use to evaluate operations. I understand that there are times when the through movement of buses from the off ramp to the on ramp will be delayed due to traffic, but there are no viable options to address this minor movement delay.
Please feel free to contact me directly should you have any further questions. And again, my apologies for the slow response.
Rick Roberts, P.E.
Washington State DOT
King Area Traffic Engineer
I replied:
Mr. Roberts,
Thank you for the detailed analysis and response. I'm very happy that complaints like mine are taken seriously. I understand that there is only so much money to go around and it has to be spent where it does the most good, so I understand the reasoning for not changing that intersection.
Thank you,
Jarrod Lombardo
