Study: San Francisco's HOV lanes increase traffic congestion
A new study of San Francisco's high occupancy vehicle (HOV) lanes has revealed something disturbing: more congestion. According to researchers at UC Berkeley and Cal State University, East Bay, in a 100 mile sample section of freeway, HOV lanes have counter-intuitively led to an increase in traffic congestion.
The study utilized data collected from sensors embedded in the pavement over 4.5 years between 2001 and 2005. As San Francisco's HOV lanes are only active for 8-10 hours per day, traffic could be measured both with and without the restriction in place, allowing for the comparison.
What they found was that not only was there no increase in carpooling, but that that when HOV lanes were 'active', traffic capacity decreased by 20-percent by increasing congestion on other lanes. A report from 2005 also noted that in areas where HOV lanes are not separated from general traffic, accident rates increase by some 50-percent.
[Sources: TheNewspaper.com, CalAcademy.org]
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Reader Comments (Page 1 of 2)
Gunnar Heinrich 7:18AM (4/03/2006)
It's the same faulty premise that if you widen the road, traffic will be less. For some cases this can be true. For plenty of others, it only makes for more snarled traffic.
http://www.automobilesdeluxe.blogspot.com
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Richard Brown 8:01AM (4/03/2006)
About time they realized this. How long does a social experiment have to fail before they admit it is a failure and makes traffic worse?
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Joe 8:06AM (4/03/2006)
Thats the precise reasoning that had NJ remove their HOV lanes. Personally, I understand why you would want to have them to encourage carpooling, but in some cases enforcement and traffic have just become a nightmare...
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Richard Warren 8:19AM (4/03/2006)
Duh! Take a lane or two basically out of service and of course it increases congestion. The dumbing down of America, then we need a research project. Things can't get more simple, ask the drivers, driving it everyday, take a few digital phots, befor-after, done.
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Paulo Becker 8:27AM (4/03/2006)
I don't see why that's counter-intuitive. If you decrease the amount of lanes people can use, traffic congestion will increase. D'uh. And since nobody wants to give up the comfort of driving their own cars to work, the carpooling option will not happen.
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Puff Chippy 8:49AM (4/03/2006)
D'uh is right. Let's see, we take this tax money to cut a lane's utilization in half, then wonder why traffic is worse than it was before. I wish the folks around DFW would figure this out and open these lanes to the public that paid for them. Maybe somebody should study how much gas THAT would save.
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charlie 8:56AM (4/03/2006)
I agree with 3. It would seem like a shitload of people would have to spontaneously take up carpooling to make up for the loss of a normal lane.
However... theres something fishy about the method the researchers supposedly used. How can they compare peak freeway hours when HOV are enabled to the off hours when the freeway isn't gridlocked anyway?
I wonder how HOT lanes compare, traffic on the special lane should be greatly increased which would take away from the other lanes.
Another great irony if this research is true is that the extra gridlock caused for the vast majority of drivers definately causes much more pollution than the benefits of people who decide to take up carpooling. LOL, I remember hearing that some states had opened up HOV/HOT lanes for single passenger hybrids. Might turn out that they were creating more pollution than they were saving.
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Kevin 9:49AM (4/03/2006)
This report is faulty. Of course congestion is going to be higher when the carpool lane is in use. Its in use at 6-10AM and 3-7PM, which last time I checked were the busiest parts of the day for traffic anyway. The only way to really test if it made it worse would be to actually remove the restriction on the lane for a week or two and then take some data. Taking data from different parts of the day is like comparing apples and oranges.
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Whiplash 10:01AM (4/03/2006)
I have been saying this for YEARS. If you limit a particular lane to a smaller portion of the population, all you are doing is reducing the bandwidth of your highway.
The reality is that NOBODY, not even "progressive" San Franciscans, are going to postpone thier drives and find somebody to ride with just to use a special lane.
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goat 10:08AM (4/03/2006)
The real point of HOV lanes is to increase congestion, so I don't know why this should be a surprise to anyone.
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pedro 10:17AM (4/03/2006)
Whiplash has a very good point: by how much time does the average commute increase by using carpooling and the HOV lanes, vs. just sticking it out in traffic.
It possible that the time spend driving to a carpool spot and/or picking people up outweighs the time saved using the HOV lanes.
Another question: if the HOV lanes ended up being a smashing success and were presumably jammed up, wouldn't then usage decrease?
Another possible use of the lane: couldn't they just let on a certain number of vehicles an hour onto the HOV lanes to reduce the pressure on the regular ones?
It seems that it would make more sense to just randomly let cars onto that lane, increasing the overal flow on the main stretch.
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James Sonne 10:50AM (4/03/2006)
HOV lanes are only active during rush hour. Outside of rush hour they are open to everyone. So this study says that during rush hour there's more traffic, and outside of rush hour and when there is an extra lane open to all there's less congestion. ... Who gives people money to do these studies? I want some free cash.
HOV lanes are a good idea in my opinion, especially for through traffic; but other drivers need to respect that it is an HOV lane and not drive slowly in the left lane. The problem arises when people don't realize that there are laws against driving in the left hand lane. Left hand lanes are always passing lanes and you can be pulled over for driving in them.
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Nathan 10:53AM (4/03/2006)
If the point of HOV is to encourage carpooling (for emissions and fuel consumption reasons), effectively increasing congestion in non-HOV lanes will only help to reinforce this agenda.
Then again, in the short term, having cars sitting in gridlock for longer periods because of increased congestion will increase emissions and fuel consumption.
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Paulo Becker 10:56AM (4/03/2006)
Here's an idea that might actually work: forbid SUVs traffic from all lanes but one.
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s 11:01AM (4/03/2006)
You should see Los Angeles! I hate it here.
Illegal immgrants go back to Mexico and fix up your own country.
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Marcello Mastroianni 11:13AM (4/03/2006)
What's San Francisco's regional public transportation like? Do they have subways like Boston and New York? That's by far the best way to keep congestion to a minimum.
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Doogs 11:30AM (4/03/2006)
"12. Here's an idea that might actually work: forbid SUVs traffic from all lanes but one."
Yeah, and how would that work, exactly?
You want an real idea that might actually work? Encourage telecommuting and staggered commute times. If you could take even 15% of the cars off the road from 7:30-9:30 and 4:30-7:00, there wouldn't BE traffic. Every day would be like Columbus Day or President's Day or one of those other holidays that schools and banks get off but no one else does.
On top of the obvious benefit of decreasing traffic congestion, everyone would see better gas mileage, emissions would be lower, etc etc.
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Jeff the Baptist 11:33AM (4/03/2006)
I have to side with Kevin. Comparing rush hour to non-rush hour traffic is poor analysis. You do not have a proper control variable. For instance:
"The study found that at 60 MPH, an HOV lane has a maximum flow of 1600 vehicles per hour compared with 2000 for the general purpose lanes. Researchers used an estimate of 1.3 or 1.4 occupants per vehicle in the general purpose lanes to calculate that HOV lanes are not able to transport more people per hour than a general purpose lane."
Just a little math shows that 2000*1.4=2800 people/hour. The HOV lanes only need 1.75 people/car to beat that. If the HOV system requires a driver + 3 slugs, the single lane is carrying more people than twice as many lanes of regular traffic.
The other issue is whether the HOV lanes allow ULEV vehicles to avoid occupancy restrictions or not. Now the HOV lanes back up as badly as the standard lanes because ULEV drivers don't bother to pick up slugs.
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Marcello Mastroianni 11:56AM (4/03/2006)
> You should see Los Angeles! I hate it here.
> Illegal immgrants go back to Mexico
> and fix up your own country.
I'll ignore the xenophobic nature of your comment and point out that recent immigrants are more likely to use public transportation, more likely to work during off-peak hours, and less likely to contribute to congestion on the highway during rush hour. So you can kick out all the immigrants you want, it's not going to solve the problem.
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Joey 12:01PM (4/03/2006)
And then they want you to take alternate transportation. So you take bart to only find out that everyone and there mother is taking it so now you have to rush to bart to find parking.Up and down the isle as train by train goes by. All this while you are thinking you should have just got stuck on I80 and pay the early bird parking fee downtown because your round trip bart ride is gonna be more than that.
And if you are like many that have to cross 2 bridges then there is toll.
I never understood why all the companies made everyone come in at 8AM. Thats one of the main reasons for rush hour traffic. So maybe instead of building HOV lanes lets just change work hours.... flex time is good too!
When I switched offices I found myself going against morning traffic.... now that was relaxing :)
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