Friday, February 27, 2009

 

Congestion Trends, And Do Two Traffic Flows Exist at the Same Time?

INRIX has released its 2008 Annual Report on congestion. (Via Tom Vanderbilt)

The key finding is "a decrease in the Travel Time Index of 3.5% from 2007; more than
reversing the increase of 1.9% between 2007 and 2006".

This conflicts with my experience and analysis of fuel economy. For most of 2008, I've felt that my drive times were longer, except in recent months. This agrees with the decline in fuel economy. For gasoline, fuel economy declined in most of 2008 and only rebounded slightly at the end of the year. It finished down for the year.

However, a little further thinking reconciles my analysis with the INRIX Report. When diesel and gasoline fuel economy is looked at, fuel economy does begin improving earlier in the year and does end as a net improvement for the year, in agreement with the INRIX report.


Here's what I think is happening.

I think there are two traffic flows that exist at the same time.
Car traffic may have gotten worse while commercial traffic became more efficient.

My thinking is that car drivers responded to gas prices by erroneously accelerating and driving slower, this worsened fuel economy for car drivers. Commercial driving habits probably didn't change much for non-freeway driving. Trucking probably benefited from decreased congestion and also improved fuel efficiency by driving at lower top speeds on the freeway. Car traffic suffered from decreased throughput at intersections and decreased speeds for non-highway driving (below 55MPH, higher cruising speeds are more efficient).

UPDATE (4/27/09): I e-mailed INRIX at the time of this post about some shortcomings in their report, I received no reply other than acknowledgement of receipt. Their reporting is based on data from commercial vehicles. Commercial vehicles behave differently than passenger vehicles. They accelerate more slowly, have cargo that shifts, hit more red lights, etc. Generally, most traffic flows around them, interfering slightly as they merge in front after passing (i.e. diminished passanger vehicle traffic flow could result in slight improvement in commercial vehicle traffic flow). Also, INRIX data compares traffic relative to "free flow" rates. A decrease in free-flow rates will exaggerate improvement in traffic flow. Their reporting also will not recognize diminished flow during non-congested hours, which can be even more costly than gains during congested hours.

Comments:
I'm confused as to how you conclude that "below 55MPH, higher cruising speeds are more efficient" based on the graph to which you link.

It looks to me like the data there indicates your statement is untrue for several of the vehicles. I've gathered data for both the 2000 Jeep Grand Cherokee Limited I used to drive and the 2006 Land Rover LR3 HSE that I currently drive. Both analytically and experimentally, they each show peak economy at speeds under 55 m.p.h.

Regards,
Rob
 
Obviously it's not always true. But it is on average. If you look at any EPA reports, you'll see that the mpg/cruising speed graph for their sample peaks at about 55mph.

Depends on engine, transmission, load, and weather too, but aerodynamics are generally the dominant factor after vehicle type. Light trucks and SUVs will often have optimal cruising speeds around 40mph.
 
EPA reports
 
EPA's 2009 Fuel Economy Guide, see page 5
 
出会いSNS【ふみコミュ】で楽しく遊んでみませんか?当サイトのオススメ機能を紹介しながら当サイトの魅力を大公開!!
 
出会い専門コミュニティ【ixim】で素敵な出会いをしませんか?楽しめる出会いを当サイトが提供します!!
 
有馬記念 2010 過去のデータから共通する勝ち馬の法則!!注目馬や穴馬などの最新情報を随時公開!
 
有馬記念 2010 過去のデータから共通する勝ち馬の法則!!注目馬や穴馬などの最新情報を随時公開!
 
芸能人と仲良くなれちゃうコミュニティ デコログ(DECOLOG)誕生☆今よりももっとずっと、楽しい♪を見つけちゃおう
 
冬休みを利用してのプチ家出中の少女が集う家出掲示板登場!困っている彼女達を救えるのはアナタしかいません。もちろん救ってあげた貴方の好きなようにして下さい。救ってもらった負い目が有るから性奴隷も思いのまま
 
ゲイにも出会いをする権利はあるのです。もちろんノーマルの方でも興味本位で登録可能ですよ、きっと女性を忘れさせてくれる位の、快楽が体験できるでしょう。専門の掲示板を無料で使ってみませんか
 
ハッピーメールフレンド掲示板でパートナー探し!アナタの理想のメル友、恋人がきっと見つかる。ここで見付けれない人はいないと口コミでも噂に成るぐらいの高評判のサイトですよ
 
このデコログでは芸能人と出会う事が出来ます。それこそが今の退屈な人生から抜け出すチャンスなのです。さあ皆さんも芸能人と出会い、上手くいけば芸能界デビュー??
 
フェースブックで出会いを探すのはとても簡単!国境を越えてつながりをもてる新しいソーシャルユーティリティサイトです!フェースブックは気軽に会話が楽しめて今大人気です!
 
Men are just passionate about these shoes mainly when coupled with jeans. Hogan Shoes SaleA couple of jeans with natural design can take on an utterly new gaze when worn with a cool sneaker.Hogan Shoes Sale Men's sneakers are also go excellent with informal. For those who take pleasure in wearing sneakers, there is truly no arguing the reality that sneakers are the essence of cool, as without risking ease the sneakers Franklin Marshall T-shirts
can be stylish at the matching time. The coolest sneakers are those which stay exact to one's own intelligence of statement and style. Whatsoever this might be, Abercrombie Fitch Salethere is definitely a sneaker to facilitate classify one's own individuality. Sneakers catch the great shape with the paramount features.Asics Tiger Shoes They are contrived with resources like canvas, leather and the fine suede. Franklin Marshall OnlineMainly, the canvas sneakers are prepared with the ecological resources. Sneaker shoes possess the love of the natives at all the ages and offer a variety to everyone, irrespective of the gender.
 


welcome to our shop,my shop website is hollister milano and Abercrombie and Fitch and Abercrombie and Fitch UK .
 
mbt shoes uk,mbt shoes london,mbt shoes uk sale,mbt sale uk,mbt footwear uk,mbt shoes uk clearance,mbt shoes sale,mbt sale,mbt uk shoes

new era france,Le magasin de France pour New Era Caps,Trouvez une grande variété de Casquettes New Era avec Livraison gratuite disponible dans le village de chapeaux,new era soldes en France online!

scarpe mbt italia,mbt store,outlet mbt,shoes mbt,mbt outlet store,,scarpe mbt,mbt online store,outlet mbt,mbt online shop,mbt scarpe outlet,mbt outlet.

mbt outlet,mbt outlet uk,mbt outlet store,mbt shoes.

oakley holbrook - oakley on line www.oakleyholbrook.it 86% di sconto.

Ralph Lauren Pas Cher,polo ralph lauren,ralph lauren pas cher homme,polo ralph lauren pas cher homme.

 
Post a Comment

<< Home

This page is powered by Blogger. Isn't yours?