Wednesday, January 3, 2007

The World (of Transportation) in a Grain of Rice

Rice demonstrates traffic congestion
Explaining how highways work is not always easy. We, drivers, typically view the world through our windshields and what makes sense from that perspective may not when considered from a broader system-wide perspective. For instance, ramp meters. WSDOT has utilized these devices to great effect throughout King County, for example. To the typical motorist, a ramp meter appears to just queue cars on surface streets, moving the backup from the highway to the local community. But to a transportation engineer, the process of controlling traffic flow makes all the difference between a highway functioning during the peak drive or failing.

So how do transportation experts explain complicated systems analysis in a way that makes sense to the rest of us?

Last September, Secretary Doug MacDonald announced the $1,000 Doug MacDonald Challenge, sponsored by the national Transportation Research Board, an organization with the National Academy of Sciences.

In his challenge, carried by the Seattle Times, Secretary MacDonald said he would give $1000 of his own money to the person who could best communicate to the public the concept of "through-put maximization," which means moving the maximum number of cars through a stretch of highway at the maximum speed.

After reviewing 258 entries, MacDonald selected Paul Haase, a Sammamish science writer with a thing for funnels, as the winner.

The Paul Haase solution
Haase suggested that anyone who has ever mixed up a recipe in the kitchen would understand traffic flow better through a simple experiment.

Here’s what you need to try this yourself:

  • Two funnels

  • Two liter-sized containers to place under the funnels

  • One liter of rice

  • One stop watch

To demonstrate his idea, Haase dumped one liter of rice all at once into the funnel and started the timer. Forty seconds (and several rice-sized traffic jams) later, all the rice was in the receiving container. Then, he took the same liter of rice, the same funnel and the same stop watch, but this time he poured the rice slowly and evenly into the funnel. Can you guess what happened? Twenty-seven seconds later, all the rice was in the receiving container. He shaved 13 seconds off his old time through gradual, controlled pouring.

The process of controlling the pour would intuitively suggest that the last "rice" in line was being slowed down. But in reality, that last "rice" in line actually arrived ahead of nearly all the rice that "jammed" the funnel during the uncontrolled pour.

What does this prove? According to Secretary MacDonald, it proves systems like ramp meters, which regulate traffic, save drivers time. It also proves future systems, like high occupancy toll lanes that use transponders to speed drivers through toll lanes, will make the most of our limited lanes.

We will continue to search for ways to talk about transportation systems. What do you think?


The Geezer said...

I am not a scientist, but a businessman. I am also observant.

You folks do a really great job of applying lipstick to that pig, but it is still a pig. Probably the director's pet pig.

Your example has nothing to do with the problem. Cars do not create friction rubbing together while waiting for that ramp signal to change, as your rice did.

Take your engineered solutions to the press all you want, but I offer this:

During the foul weather, when the ramp meters were shut down, traffic moved faster.

You put signals even when there is an add lane, and no merge, as in Nbound on the N. 175th entrance ramp. Just to irritate the locals, I suspect. Oh, I am a local.

And those HOV lanes? Were any of you around during the three days that the 405 transition took place moving the HOV lane from the outside to the inside? I was, and each day there was no HOV lane, the added capacity made ALL the traffic move at near the speed limit.

You sellin', but the Geez ain't buyin'.

Of course, you are the same guys that had on your website two days ago that SR 9 went through Carnation, and that SR 9 and 530 were at Granite Falls. Heck, your folks don't even know what towns your highways run through.

The Geezer

smith said...

What this doesn't cover is the nearly twice the cost of energy to use ramp metering. I drive on SR-520 every workday and the ramp metering really doesn' t do much to increase the flow of traffic. I have an instant mileage readout which shows I am getting between 0 and 40 mpg. Most of the time in stop and go traffic the mph reads 0 to 8. It usually takes me 45 minutes to go 12 miles. Even a Prius couldn't claim good mileage. At least a third of the vehicles on the commute are SUV types, the rest are sedans like mine and now and then there is a Prius or some other hybrid on the road. The aggregate mileage is probably 6 mpg. I have stopped at the 148th and SR 520 ramp meter then accelerated into a jam up 1000 feet ahead. Not only that, cars are driving on the shoulder to get ahead. The five choke points on SR 520 are a test of patience every day. The worst of course is the SR 520 westbound to I 405 northbound jam up. The rest of the choke points are about 90 % of that. The only way to move traffic the 12 miles across the lake is by mass transit. Six lanes will only increase the wait times at the new choke points.

Joel Johnston said...

It seems that employees of the State of Washington are bent on getting toll roads in our State. I am not a supporter of this concept, and I would need to see a demonstration of sound management of our DOT prior to ever voting for it.

I do have a few suggestions. I am not one to blame our DOT for all of our problems, but for the mismanagement of the problems.

For example, it seems that the Counties and the Cities are irresponsible for not doing their part to improve our traffic. It's crazy that they all build roads to dump traffic onto our Interstate Freeways, rather than responsibly building roads that compliment our freeways. Why not pass a law that requires the local community build roads that can accommodate a certain percentage of the traffic they direct to our freeways. The only method of getting from Mill Creek to Kent, as an example is on the freeway.

And, it seems that with some public service announcements that demonstrate better driving habits, we could improve the situation. As an example, maybe people could learn how to properly merge - by going the speed of the other traffic when they merge, but following the lines and not merging early to block traffic, etc.

I personally think there are plenty of ways to fix our problems without tolls and more concrete and asphalt.

The Geezer said...

Geez here again.

Joel Johnson is a smart youngster. Must live in Bothell or sumthin'.

The problem is exacerbated by our currently low level of driving skill. When my Daddy taught driver's ed--both parts, book learnin' and the behind-the-wheel, we learned real courtesy, not "Seattle polite" courtesy, how to merge (get up to freeway speed, pick a spot, and merge) instead of doing "Seattle polite" and braking on the freeway to let some schmuck in.

If there was a slowdown, and we got past it, we then moved out, instead of lolly-gaggin' around for another mile or two, before punching it up and returning to road speed.

I place root cause at the effs who pass for driving instructors, both public and private, who do....what? when teaching folks how to drive.

And I shall not rest until I clearly suggest that anyone from the DOT take a ride with me at commute time, and I will gladly point out to them what the cause of this or that delay is. Get them away from their fancy-schmancy computer programs, and get them out on the road to actually take a look at what is happening.

Now, to be fair, I should note that the director was out after our "big" snow event a month ago, driving the freeways at 4 Ayem, and getting some experience first hand. Too bad he was in a state SUV with a driver, rather than getting the full experience.

Geez rests.

geowreck said...

if you would have the troopers start to enforce the tailgating laws, traffic would move much better. its hard to merge when everyone is about five feet off the others guys tail. not only is this dangerous, it really screws up the flow of traffic. the choke points are mostly caused by merging traffic that can't get in. also, the carpool lanes are a waste of money. judging from the amount of traffic i see all day, a large percentage of us don't work 9 to 5 at the same location every day, and carpooling just isn't feasible. put the money into longer merge lanes, instead. finally, what is comment moderation? sounds like censorship to me

The Geezer said...

GEOwreck at #5.

I thought moderation is CS too. So, I made a public disclosure request for those comments NOT approved, to see how closely they monitor. If you would like a copy of that response when I get it, write offlist, since you didn't link to your email or profile

The Geezer
thespinmeister (at) gmail (dot) com

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