Look, Ma, no brakes

Cures for congestion can come cheap

Posted by Eric de Place (Guest Contributor) at 4:48 PM on 04 Jan 2008

Read more about: placemaking | cars

When I was a little kid, I remember being stuck in gridlock on I-5. (Seattle had congested freeways even back in the 1970s, shocking as that sounds.) And I remember being perplexed that all the cars would slow down in heavy traffic. Instead of spacing out so far, I wondered, why couldn't they all just maintain 55 miles per hour and drive inches apart. As long as everyone agreed to drive the same speed and not hit the brakes, heavy traffic wouldn't require us to slow down. Right?

My parents didn't get it. Typical parents.

I changed my mind sometime after I got my driver's license. But now it turns out there's evidence that I was right all along.

A recent study by the National Academies of Science found that distracted drivers -- especially those with cell phones -- create congestion, mainly because they drive slower than the normal flow of traffic. And a new European study finds that excessive braking is a prime culprit for backing up highways. I told you so, Mom and Dad!

I guess the real lesson here is that there are some surprisingly small things we can do to ease congestion. Driver education and awareness, for example. Banning cell phones on the road, maybe. New technology that helps drivers brake smarter and more safely. There are probably dozens more little fixes that cumulatively could add up to meaningful relief.

On the downside, however, these fixes don't require blue-ribbon panels, or new layers of regional government, or big new taxes for instrastructure (sarcasm). And so politicians can still be accused of not doing anything about the traffic headache. But even so, it might be worth considering things we can do right here and now -- and for cheap -- to help ease highway congestion.

For story: Look, Ma, no brakes
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Transportation School

To somebody who used to teach transportation planning and environmental impacts, you sound just like some of my first-day students. Its OK, but a fascinating topic should ever want to take a course on it.

A little math is involved, but what you'll see is that as a highway approaches its capacity the traffic will start slowing. Example: is you have a roadway designed for 150,000 vehicles a day one-way but put 185,000 vehicles on the same highway, it has to slow down. There are even curves that show vehicle count to volume ratios against peak and non-peak speed for many highway designs. Unfortunately, the math works perfectly until you start talking recurring and non-recurring incidents (vehicle accidents), when is becomes even WORSE; we don't graph those puppies.

I hope I don't sound preachy but it's cool stuff. Advanced classes go into a logit delay equation which if you know some math is pretty darn cool. There is also a quadratic equation that takes into account wind resistance, drag, wheel friction, and torque which tends to average out the most economical average speed of perhaps 47.5 MPH. Those Prius can probably do better by the way, more an an aerodynamic design.

Wish I could load it up in a spreasheet and show ya!
sammie

Onward through the fog

by Sam Wells at 6:09 PM on 04 Jan 2008

We need more people driving slower but steadily

Part of the reason people keep braking unpredictably is because they are trying to speed which gives them little time to react in any way other than to slam on the brakes. I keep my top speed to the limit inside of always trying to drive 10 km/h too fast (10-20% faster than the limit). I would estimate this typically slows me down only about 5-10% and I probably save at least 5% on gas because of less wasteful acceleration.

I also think we need to slow down more (i.e. slower speed limits) to reduce the speed advantage of cars over bikes/transit. Once people know that a 10K commute only takes 10-15 minutes longer they might be more open to cycling.

by katakanadian at 8:30 PM on 04 Jan 2008

Good Point; Grandma Driving Cycle

I have commented many times on various blogs that driving smoothly can reduce emissions and fuel consumption maybe 10% as opposed over-speeding and "jack rabbit" acceleration. That doesn't sound like a lot, but let's say New York City regional drivers consume 5 billion gallons a year, 10% is a lot of juice! [No idea if the numbers are right - you get my drift.]

Well it turns out that nobody drives smoothly anymore, "the Grandma driving cycle," and the original drive traces done decades ago were worthless. That driving "trace" or pattern of driving was made much more aggressive for laboratory testing and even the fuel economy for the Prius dropped by about 15%. Ouch!

How did scientists figure out that people were acting wild with the gas pedal and brakes? Interesting question, since they couldn't use anecdotal evidence. Nope, the fitted a bunch of small, GPS and data acquisition computers in some cars in five cities starting in LA (Five City Test). Lots of work processing all that hooey, I'll give them credit. Results were astounding. People basically drive like horse's asses. Equally weird was that the truckers seemed to be hopelessly lost.

But I digress, it would be nice if people would ease off on the gas pedal a wee bit and save some serious money. Changing human behavior, however, is a different animal. /sammie

Onward through the fog

by Sam Wells at 10:49 PM on 04 Jan 2008

Ant traffic jams

They don't happen very often. Why?

Because each ant keys off the next ant. It's a kind of distributed hive computing. A fractal governs the interaction.

If each car had a proximity device that keyed off the car in front to keep speed coordinated, no more acordion accidents or traffic jams. At least a lot fewer.

Just like a distributed power grid would work as well. Each internet enabled device controlling each load and power source keying off the devices next to it on the grid. Keeping the power flowly smoothly.

http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin

by amazingdrx at 12:49 AM on 05 Jan 2008

In what way would this be a cure for congestion?

Increasing the speed at a particular degree of congestion will increase the value of property development further away from the destination which helps increase the average distance driven which increases road usage ... until we can get the same amount of traffic slow down as before, just with more gasoline being burned in the process.

Reducing the mode share of automotive traffic ... that is a cure for congestion. Investment in more road capacity is an investment in more congestion.

Virtually Yours, BruceMcF Energize America 2020

by BruceMcF at 2:03 PM on 05 Jan 2008

Mode Choice Model

Excellent point in your second paragraph, Bruce. transportation mobility is just not cars, but may apply to mass transit, bicycles, and yes, walking. Complex models are constructed to describe the patterns of mode choices, which sometimes involve interesting combinations (e.g., bike racks on buses).

The resulting data is parsed by transportation activity zone (TAZ) and reported as "mode split" in fairly large tables. To lower single occupancy vehicle (SOV) driving, one would obviously want to create incentives for other mode choices. /sammie

Onward through the fog

by Sam Wells at 6:27 PM on 05 Jan 2008

Have y'all seen this?

The fluid dynamics of traffic jams

Not specifically about fuel usage, but an interesting way to think about traffic.

by willa at 7:56 AM on 06 Jan 2008

The weakest link.

Around our way most of the apparent congestion is caused not by fluid dynamics but by horrendously inefficient intersection design. Frequent stoplights bunch traffic into dense little pods that leave most of the road empty much of the time, until the next pulse of closely-spaced vehicles comes through. What a waste of land, of blacktop, of people's time, of clean air with all those idling engines.

The true meaning of life is to plant trees, under whose shade you do not expect to sit.

by spaceshaper at 11:14 AM on 06 Jan 2008

ADVERTISING POLICY

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