The Antiplanner and other advocates of technical solutions (as opposed to behavioral ones) to environmental problems have long argued that relieving congestion is an important way of saving energy and reducing pollution and greenhouse gas emissions. But this is difficult to quantify.
A recent analysis from University of California researchers finds that relieving congestion on Southern California roads could reduce auto-related CO2 emissions by 30 percent. This is more than even I had expected.
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The analysis found that three different strategies could each reduce emissions by 7 to 12 percent: Congestion mitigation, meaning things like ramp metering and congestion pricing; speed management practices that reduce excessive speeds; and traffic smoothing, meaning things like intelligent transportation systems that reduce stop-and-go traffic. Combined together they would reduce emissions by 30 percent.
Of course, Southern California is the most congested corner of the United States, so the results may be lower in other parts of the country. But the truth is that most major urban areas today are terribly congested. So while congestion pricing is probably not going to do much to reduce emissions in Fargo, it can do a lot in places like Atlanta, Boston, Seattle, and Washington. Too bad most urban planners are trying to make congestion worse, not better.
What if you are an urban planner that supports congestion pricing?
This is a useful paper that can help explode some myths about what contributes to reducing carbon emissions and what doesn’t.
Although it hasn’t been suggested often, it’s occasionally proposed to reduce freeway speed limits as a means of controlling carbon or pollutant emissions. If the curves in Figures 5 and 6 of this paper are correct (and I’m reading them correctly), carbon emissions don’t vary much per vehicle mile at real-world average speeds between 35 and 70 mph. The paper authors describe the zone of indifference as 40-60 mph. However, they suggest that speed be reduced to 45-55 mph as an emissions-reduction strategy, based on the slight inflection in the theoretical fuel efficienct that occurs between those speeds.
This would impose an enormous time cost, and pose terrific problems of enforcement. It would also confound any efforts to smooth traffic flow, as motorists’ differing response to the speed limit causes passing and weaving maneuvers that worsen the flow and cause crashes. The authors are not correct in stating that lower posted speeds on freeways are “safer.”
In places where speed limits are egregiously low (and 45-55 mph on a freeway is egregiously low), it is frequently possible to smooth flow and improve safety by RAISING the posted limit. This has the effect of making vehicle speeds cluster more narrowly around one value, eliminating very slow and very fast speeds. Often the average speed falls slightly after the speed limit is raised. These results were seen after Michigan’s recent program of raising most urban freeway limits to 70 mph.
Is SoCal the most congested? I thought according to that TomTom study released a month or two ago Seattle was the most congested MSA.
Too bad most urban planners are trying to make congestion worse, not better.
Bulls—.
Nonetheless, it is ridiculous on its face to try and assert ‘an enormous time cost’ about a few miles an hour. Fatality rates at higher speeds notwithstanding, we all know that on surface streets that slower speeds not only are safer, but less congested as sudden stops propagating backward are worse at higher speeds. Maybe more vehicles having radar will lessen this problem.
We will see whether large, costly infra projects to lessen congestion will get built when we have $Ts in backlogged projects already.
DS
I thought something similar to this in a seminar discussion a couple years ago at the CNU conference in Austin. Conversation had drifted to whether or not new urbanists should actually HELP create congestion to get people riding public transit and promoting walkable neighborhoods and increasing density. I was disgusted, both for the economic disadvantage this would cause and the increase in emissions. I thought that cities should just spend a considerable amount of money on a traffic engineering project that times traffic lights perfectly (or as perfect as possible) and holistically throughout the entire city and leave the merits of new urbanism to stand on their own because there are merits and a market for it. Perhaps ironically, the next seminar after that I attended at the conference was a detailed economic analysis of market demand for New Urban development, led by an economist from the University of Michigan who believed New Urbanism has a stronger future outside of government mandates.
With Dan and Spokker on this one O’Toole. Statements like “Too bad most urban planners are trying to make congestion worse, not better,” and the accompanying assumption that planners are somehow against congestion pricing (a brainchild of government planners) is idiotic.
I know how hard it must be to come up with a good new post every day, so I’ll just chalk this up to a bad day diarrhea of the ideological subconscious. Better luck tomorrow.
I like technology solutions also, Randal. I prefer smaller vehicles such as motorcycles, mopeds and minicars that don’t take up as much space on the road. I like to think above the box and think in four or five dimensions – grade separation, length, width, height, time, dollars. The result of this type of thinking is elevated personal automated transport – increased capacity, lower cost, better safety, reliability, less air pollution.
The problem is that planners (and the Antiplanner) keep measuring against “congestion”. I don’t know why they do that. Congestion (or lack of congestion) is not something that should be a goal.
The goal is that people get to where they want to go — preferable quickly, safely, comfortably and cheaply. Congestion is only indirectly and inconsistently related to that.
Suppose you have two cities and the only transportation bottleneck between the cities is a river with one bridge which causes congestion. If you build a second bridge doubling the capacity, and yet the congestion is the same on both bridges, what have you accomplished? You have doubled the cost of crossing the river, and have the same congestion….. BUT now twice as many people get to where they want to go at the same level of speed, safety, comfort and price. Twice the cost, twice the benefit, and the same level of congestion.
The real world is different than that, but the point is still there. Congestion means unmet demand — it is not a measure of success. The measure of success is improvement in number of people getting to where they want go, with factors of speed, safety, comfort and price.
Congestion (or lack of congestion) is not something that should be a goal.
It’s not.
Thanks!
DS
Hey Dan, look up “liar” and “hypocrite” in your new Thesaurus, then double your medications and meditate on their meaning.
On December 19th, 2007, Dan said:
The idea is to reduce discretionary trips during peaks to reduce congestion.
Thank you Andy, for that hypocritial comment.
DS, While I agree with the spirit of the comment about surface streets I’m not sure we’ve ever properly studied congestion on them, at least not to claim they’re less congested than freeways, especially relative to the amount of traffic they carry.
Regarding Greenhouse gases, speeds etc etc, there is a companion Article in the same “ACCESS” published by UC Transportation Center with further specifics. I’ll comment on it also separately.
But regarding Aaarne Frobom’s concerns about adding congestion by reducing freeway speeds I suggest the opposite is true. An earlier Article in the Fall 2005 “ACCESS”,(Prof. Pravin Varaiya), shows optimum throughput is in the 45mph to 50 mph range, coinciding well with the minimum GHG. And the speed penalty is severe; at 65mph a loss of about 37% in throughput. Smooth speeds are also important.
This Article also shows why HOV/HOT lanes are unfavorable to overall freeway throughputs.
Andy, Google “LOS” and get back to us with your tap-dancing as to why your comment shouldn’t be ridiculed. Everyone inhale deeply and don’t exhale until Andy tells us why throughput isn’t managed and planned to a binary service level set.
And thank you Walt for reminding us what is planned for on the ground, and why folks who post on their blog aren’t at the table.
DS
Hey Dan, you definitely should not exhale. Hold it in and let your mind wander … you could imagine a world where centralized planning, in say Cuba, was still better than a nearby island, say Haiti. Take pleasure in that thought; and don’t let other examples undermine your self-esteem.
If this doesn’t help, ask one of the psychiatrists at the hospital there to adjust your meds.
And thank you for proving my point about planners and congestion. You saved me a few minutes of typing! You are such a nice commentor on this website — my favorite one! You are a good, good boy.
[/killfile]
DS
[/snark off, mission accomplished]
In the Current Fall 2009 “ACCESS†from University of California Transportation Center, there is a companion article, “Moving Los Angelesâ€, (no, not moving out to escape taxes etc!). It is based upon a RAND CORP study for short term improvements to increase mobility coupled with the congestion mitigation, speed and traffic factors in the GHG article.
Generally supportive, but there are a few bumps in the road.
The major recommendation for congestion pricing is in principle favorable; reduce peaks in high demand periods by smoothing demand over longer periods. Good for many cities. However LA has “been there done that†to a great extent voluntarily, through offset work hours, delivery schedules, flex time etc. Whereas many cities have “valleys†between peak demands of 40% or so, LA’s typically are in the 10% range. Thus not a lot to gain left. Indeed LA’s daily vehicle-mile per lane mile of ~24,000 is about 20% better than a very few other large cities. It is about 40% better than average cities.
Unfortunately the recommendation for congestion pricing is a network of HOT lanes, not ones that toll all lanes. There is ample evidence, (see also the Fall 2005 ACCESS, Prof Varaiya, “What We Have Learned About Highway Congestionâ€.) that freeways so equipped reduce total people throughput. Also from Caltrans I-15 measurements near San Diego that an undesirable level of congestion must be maintained to allow tolls income to exceed operation expenses. I’ve confirmed the LA & Orange County reduced throughputs from Caltrans reports. The vehicle capacity lost in the HOT lanes to make them “attractiveâ€, imposed on the GP lanes creates more total freeway congestion than saved by slightly higher carpooling.
So indeed smooth traffic on all lanes, in the same Prof Varaiya report, shows about 50 mph for optimum throughput, and also minimum GHG as the UC report shows. A 40% throughput reduction occurs at 65 mph for example. Intelligent interactive ramp metering offers better promise for this superior performance, with less operational complexity, toll collecting, etc, etc. The use of tolls is also subject to political diversion, such as mass transit, and general funds. Cowboy drivers may not like 50 mph, but during peaks it is better than slower stop and go.
2,000 vehicles/lane/hr is achieved already with modest ramp metering, superior to HOV/HOT equipped freeways. There is potential for more. And more freeway capacity at a given demand level reduces on ramp queuing also.
Triple convergence, (aka induced traffic), is called out as deterrent to congestion reduction by building more lanes. Unfortunately the examples experienced are for situations where capacity is so far below demand; the additions still leave a major gap with demand. Buffalo NY, one of the least congested large cities shows how maintaining capacity more than demand can nearly eliminate congestion. Many cities are so far beyond the tipping point only aggressive double decking, etc, could overcome political land restrictions etc. LA on a short stretch of the Harbor Freeway has demonstrated double decking success even though it is hampered by HOV rules.
Thus if space for roads to meet demand is prevented, the foundation lies for aggressive truly innovative system R & D for ways to pack more cars on existing roads safely, or the emerging field of automated personal transportation which is beginning to appear overseas based on early USA concepts.
Emphasis on personal transportation is the key to acceptance by the public and for commercial use.
It is unfortunate that “Moving Los Angeles†conveys negative thoughts, and an attitude favoring restrictions on parking, reducing travel, etc. While it lists many of the feasible “smart growth†walk/bike, mass transit, telecommuting, etc modes, the odds of sufficient added capacity by them facing future growth is near negligible. Example San Diego after 20+ years spending over 1/3 total transportation budget on mass transit absorbs only 2% of travel. To even absorb a 1% per year increase in travel would require adding the capacity of the entire current mass transit system every 2 years.
So again, back to the innovation drawing board.
Using the oft-quoted; “we can’t build our way outâ€, (with roads), doesn’t answer why we can with mass transit plus a few fringe improvements. There is implication we have to travel less, without explaining how the number one community responsibility, to provide goods and services efficiently will be maintained or made more competitive in the global market for prosperity.
Figure 1, shows the 35 year unfortunate national mismatch of road capacity with miles, (10% road increase for 47% population increase), But despite this, Vehicle Miles Traveled have managed to increase about 170%. Why complain, the GDP per capita has increased 100 percent? Considering the estimated $ 60 billion loss per year due to congestion, there is great potential for finding truly innovative ways to provide personal transportation in urban regions. With GDP/capita shown proportional to personal vehicles /capita worldwide, USA now tops the list of large countries.
The short term improvements the UC and RAND reports recommend are marginally useful. To maintain productivity momentum, looking ahead to 2050 as many regional plans now do, truly new concepts at the systems level are needed to replace current attempts just to revive long rejected 100+ year old transit concepts, and inefficient use of limited roads.