January 23, 2007
CRC Open House Question # 3
Narrow lanes and a lack of shoulders slow traffic on the Interstate Bridge. A new bridge should feature wider lanes and shoulders to improve the safety and flow of travel.
January 23, 2007 11:16 AM
show me the research that proves this assertion ...
January 23, 2007 11:36 AM
Lenny Anderson Says:
I guess we can look forward to spectacular high speed crashes instead of fender benders as the result of our $2Billion investment.
The existing bridges can be managed to maintain maximum thru-put and safety by keeping speeds in the 45 mph range....its only for a mile or so.
There are many low cost strategies for reducing incidents which account for 50% of congestion.
January 23, 2007 11:52 AM
Paul Edgar Says:
In a direct answer to that question or statement that narrow lanes and limited sholders reduce the flow and safety of traffic on the I-5 Bridges the answer has to be yes. But these conditions are a much lessor problem then the Hayden Island on and off ramps and how SR-14 connects to I-5 north of the bridges.
People have remember that these current I-5 bridges effectively meter traffic better then tolls, or any TDM effort to match the existing capacity of the inter-connecting freeway system in Portland. You pull then off and we have real problems and that is what would happen with the CRC Project recommendations.
Until Portland is ready to invest $8 to $10 Billion Dollars into the I-5 corridor, we are a long way ahead of ourselves with this CRC Project.
WSDOT people are now telling us that they see this CRC Project at a price tag of approximately $6-Billion Dollars if it goes through. These extra dollars are for the rest of infrastructure needed to make these recommendation work.
It is a very slipery slope that these CRC recommendations are taking all of us down. There are alternatives and they know it but that is not how they make a living. This team was put together to build a bridge, justify it by selling the public that there were NO other options.
January 23, 2007 12:27 PM
Ross Williams Says:
One question that I think needs to be addressed is whether the "wider lanes and shoulders" are essential or not. If I recall correctly, they took the wide shoulder out on northbound I5 in order to add another traffic lane. Apparently it was not essential for safety. Are these really safety features or are they just reserve capacity that can turn into traffic lanes at some point in the future.
It is also important to understand that the highest throughput of traffic is going to be at speeds between 25 and 40. So the reduced speed of the narrower lanes actually increases the number of vehicles that can get across the bridge in the same period of time. Wider lanes and higher speeds require more traffic lanes for the same amount of traffic.
January 23, 2007 1:57 PM
Tom Mielke Says:
The cost has already blossumed into the $6 Billion by the time all of the infrustructure to make it work is put in place. When I quoted that figure at the RTC meeting, Don Wagner (WADOT) was real quick to correct me and say it was $2 Billion.
First... the I-5 bridge is already three general purpose lanes and the proposed I-5 bridge will also have three general purpose lanes.
Second... It's in good shape and along with another bridge, it will help handle the capacity.
Third... We need an additional bridge and corridor! This corridor is full and was recognized ten years ago by both a Washington delegation and an Oregon delegation as being full. It's full all the way through portland!
Already into cost over runs, start over without an agenda.
January 23, 2007 2:20 PM
Paul Edgar Says:
Tom Mielke is a welcome addition to this blog as a former Washington State Representative who for 8-years set on the House Transportation Committee in the Washington Legislature.
If I remember correct Tom was also the delegate from the House Transportation to the national organization that developed transportation legislation across America.
January 23, 2007 5:12 PM
Just "hmpf". Nothing more, nothing less needs said. This new bridge is just a preposterous idea. Rebuilding what in effect we already have isn't very smart.
As for wider lanes and blagh blagh balgh. Yeah, of course that'll increase speeds. Increased speeds mean more throughput. But what about the bottleneck of the south I-5 stretch between downtown and the bridge then?
That's a major problem.
So no matter what. I end up with a frustrated "hmpf".
This is not looking at the problem, this is looking at an "effect" of the core problem. The problem isn't the bridge, the problem is the interstate alignment itself. Going back even further to that to the core of this whole problem is the fact it isn't market based, is run by the Government, and has no price basis regardless of whether it is 2 Billion or not. It's all "free" to the people going across.
So again, I digress.
January 23, 2007 5:45 PM
Bob R. Says:
Increased speeds mean more throughput.
Unfortunately this isn't actually true.
Reaction times are constant, and braking effectiveness from higher speeds is decreased, therefore stopping distances increase in a nonlinear fashion related to speed - separation between cars becomes greater.
At some point, this has a diminishing effect on throughput in terms of vehicles per hour.
Depending on the roadway, maximum throughput is actually achieved somewhere in the 35-45mph range and then starts to fall off as speeds increase.
- Bob R.
January 23, 2007 7:12 PM
Erik Hovmiller Says:
How wide are we talking about here?
It's my experience that wider traffic lanes make people feel less vulnerable and safer (which maybe they are), enabling speeders to go even faster while the law-abiding folks do their thing. This creates a larger disparity in speed differences, introducing other safety and civility issues. In general, I dislike driving on excessively wide-laned highways because people seem to be less attentive and more reckless. I have absolutely no data to back up this assertion, however.
So, I'm sure we'll leave it to the uni-disciplined experts to decide what's best based on their individual field of study without them ever fully considering the indirect ramifications. *cynicism*
January 23, 2007 7:20 PM
Don't get me wrong, shoulders are a good idea in general, but they have a cost benefit analysis with them: Most tunnels, (for instance,) don't have shoulders, because the increase in safety isn't worth the cost of digging what is basically another lane. The cost benefit analysis is very simple: If adding shoulders increases the project costs by $200M, and would save 4 lives a year, then $200M*6%/4 means that each life is worth $3M. The average human isn't worth $3M though, the airlines calculate that the average person that flies on airplanes (which is the upper 80% of the population,) is worth slightly less than $2M, and so the average driver is worth less than that, which means that money spend improving safety above that level is better spent in other ways. Since we don't know how much shoulders will cost or how much they will improve safety, we can not decide if they are a good idea or not.
What they are claiming that wider lanes will do is increase the maximum safe speed, which is correct, but that doesn't actually improve the flow of travel. The current safe speed with those lane widths and the hump is 45 mph. The average speed northbound during rush hour in the bridge influence area is currently 22 mph, but even if they build a new bridge, it will only increase to 30 mph, much less than the 45 mph that the bridge can currently handle. What wider lanes help are the people that are traveling outside of rush hour, when the flow of travel is a lesser issue.
January 23, 2007 7:29 PM
Chris Smith Says:
I actually think that safety is one of the better arguments for spending money in this corridor.
But I'm not sure lane width is that compelling as a way to improve safety.
I'm more interested in shoulders, both for safety and because having a place for breakdowns is critical to improving the reliability of the corridor (non-recurring congestion, including accidents is one of the biggest sources of congestion in the region).
January 24, 2007 8:52 AM
Lenny Anderson Says:
My guess is most incidents occur on the approaches to the bridge as traffic slows due to the merge-lane less on ramps from Hayden Island and SR14. I trust there is data.
Removing these offending on-ramps as per Jim Howell's arterial bridge concept would smooth things out considerably and at much less cost.
Safety as a reason for a new bridge is a late comer to this debate; indeed when I mentioned the "50% of congestion due to incidents" figure during the latter stages of the I-5 TF, consultants denied they had ever said it.
There is something perverse in the argument. Image an old highway with curves, narrow stretches, handsome trees, etc. and a 55 mph speed limit. Most of us drive the speed limit and are fine. Every once in a while some fool drives the road at 70, misses a curve, and becomes a statistic.
Over time "data shows" that the road is unsafe, so millions are spent to straighten it out, widen it, so that it can be safely driven at 70 mph, but of course the posted limit is still 55 mph. The old charm of the road is lost, trees are cut, speeds are up, crossing is more dangerous and now the fools make it through at 80mph. What have we got for our millions?
January 24, 2007 9:01 AM
"show me... " etc etc.
Do a search on "interstate design", "interstate throughput", "lane width speed", etc. You'll end up finding treasure trove of information out there.
As for the lane sizes, widths are small will cause people to drive slower (untrained drivers), and wider lanes cause people to drive faster (untrained drivers). Trained drivers, and drivers who have much higher vested interest in driving (such as in Germany, where it costs thousands just to stay licensed per year) often are not affected by such measurements. They tend to drive whatever the safe speed is for their particular vehicle. Thus on the autobahn they travel about 150mph on lanes as wide as our interstate lanes, and about 55-60mph on lanes the size that are on the I-5 bridge. But Americans (and yea, I exclude myself from this because I have certs, licenses, and other things that are proof I can drive) generally tend to slow down in small lanes, speed up in wide lanes - it's a real lemming effect with America. Sad sad indeed.
But I digress...
January 24, 2007 10:18 AM
Paul Edgar Says:
Lenny I too support Jim Howell's contention that we can build access roads to Hayden Island. I talked to Jim last night at the CRC meeting and he suggested that this term of "Arterial Bridges" probably is a misnomer and what should be used is just an access route from Marine Drive.
The key element is that these Hayden Island on/off ramps should disappear, there are better solutions that can dramitically impact I-5 corridor safety, capacity and congestion levels.
This can be done without a new CRC Interstate Bridge replacement project and tie perfectly into the Delta Park Widening Project.
January 24, 2007 1:04 PM
Terry Parker Says:
“Narrow lanes and a lack of shoulders slow traffic on the Interstate Bridge. A new bridge should feature wider lanes and shoulders to improve the safety and flow of travel.”
This may be true, but what slows traffic down even more are the number and design of interchanges close to the bridge on both sides of the river.
On Tuesday January 22, 2007, I had some business to take care of over in Washington. Using I-5 to cross the Columbia about noon time, northbound traffic was backed up at Delta Park, however it was not the bridge causing this back up. It was the Delta Park, Marine Drive and Hayden Island interchanges creating the backup. By the time I was in Washington, traffic was free flowing again. The current and older northbound bridge was not a barrier.
This is a good example of why a middle ground option, one that retains one or both of the existing bridges along with a local motor vehicle access route and/or bridge to Hayden Island must be reinstated, priced out and carried through to the end of the entire process. With only a no build option for comparison, I do not believe a having the taxpayers finance a big new bridge can be justified.
January 24, 2007 10:08 PM
Erik Halstead Says:
Let's do an experiment.
Let's barricade off the shoulders (using concrete jersey barriers so they can't be easily moved), and one lane of the I-205 Glenn Jackson Bridge - in each direction. Further, let's restripe the remaining lanes to remove about one foot per lane.
I bet $1,000 that within three days afterwards that we'll see why the Glenn Jackson was built the way it was built. Let's not make a jackass decision to cheapskate on the I-5 bridge. Whether you like or dislike the idea of an Interstate Bridge replacement, there are certain standards for interstate highway constructon that have been established for a reason. The only reason the I-5 bridge is the way it is, is because it predates I-5.
We wouldn't dare talk about building a cheapskate MAX line by building the two tracks so closely together that trains couldn't pass each other, and deciding to artificially reduce the speed limit to 45 (instead of 55) and removing the signal system, would we? (Heck, that'd reduce the cost of future MAX construction by at least 1/3rd!!)
January 24, 2007 11:23 PM
Steve Beattie Says:
Actually, there's a third safety issue with the I-5 bridges, one that cannot be replicated with the Glenn Jackson Bridge, and that's the restriction on sight distance due to the "hump" for barge traffic. That is, if traffic on the other side of the hump is stopped or slowed due to an accident or just from congestion, you may not have enough time/space to stop when you crest the hill and are surprised by slowed traffic ahead. It unfortunately combines badly with the other issues (no shoulders/narrow lanes), as they limit options for performing emergency avoidance maneuvers.
(The eastbound tunnel on Highway 26 at the bottom of Sylvan Hill has a similar issue, but usually traffic is backed up beyond the tunnel entrance and so is visible to traffic descending the hill, mitigating the issue.)
I agree with Chris, safety is the only reason I could consider a justification for replacing the I-5 bridges (I personally hate driving over them, and try to use I-205 when I can), but I think we have more urgent transportation priorities, and that $2 Billion used elsewhere could have a more positive impact on the region and freight throughput.
January 25, 2007 5:43 AM
Ross Williams Says:
deciding to artificially reduce the speed limit to 45
I haven't noticed the Max going 45 mph through downtown. We "artificially" reduce speeds for safety reasons all the time. And unlike MAX, reducing the speed to 45 mph increases the throughput of vehicles when the bridge approaches capacity by allowing vehicles to operate closer together.
there are certain standards for interstate highway constructon that have been established for a reason.
Yes they were, but do those reasons apply here? Almost all freeways are designed for maximum throughput under free-flow conditions. But those aren't the conditions on I5 when it is congested. Wide lanes cause people to speed up, but they can't do that safely when there is another vehicle a few feet in front of them. So, far from a safety improvement, wide lanes entice people to drive faster than is safe under congested conditions.
January 26, 2007 9:56 AM
A new bridge should feature wider lanes and shoulders to improve the safety and flow of travel.
Yes. If we put money into a new bridge, put in wider lanes and shoulders. But those wider lines and shoulders, in and of themselves, are not a reason to build a new bridge.
Hey -- want safety? Narrow each bridge to two lanes. Wider lanes, wider shoulders, and more safety -- for the cost of restriping.