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Old 12-09-2008, 01:14 PM   #1
AVANTI R5
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Default Limited Access HOV Lanes Increase Accidents



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Three years ago, Texas researchers discovered that the most common form of High Occupancy Vehicle (HOV) or carpool lane was associated with a significantly higher risk of injury accidents.

A recent University of California study now suggests a remedy intended to reduce HOV lane risk may actually be making the already dangerous lanes even less safe. Researchers with California Partners for Advanced Transit and Highways (PATH), a joint venture of the state Department of Transportation and the University of California, looked at accident data for two types of carpool lanes in California.

They considered 279 miles of “continuous” HOV lanes, primarily in the northern part of the state, where drivers can enter or exit the HOV facility at any point. The report then analyzed another 545 miles of “limited access” lanes that used either painted stripes or flexible plastic barriers to restrict cars from entering or exiting except at pre-determined locations.

Although the limited-access lanes promised smoother travel with fewer interruptions from general purpose traffic, they also delivered deadlier travel. “Rear end and sideswipe collisions together comprised over 90 percent of all collisions in both facilities,” the report stated. “Higher Property Damage Only collision rates were observed in both the HOV and left lanes of the HOV facility with limited access. The combined injury related collision rates for the HOV and left lane was higher for the limited access.”


The California study avoided comparing the HOV lane accident rate with general purpose lane accident rates, as HOV remains popular with the public agencies that fund research. In 2005, however, the Texas Transportation Institute found that during peak traffic times, traffic in HOV lanes could at times move up to 35 MPH faster than regular lanes, which is consistent with the fundamental theory behind HOV.



When slower cars tried to merge into the faster HOV lane, they were often rear-ended by traffic unable to slow down in time. Likewise, the faster HOV traffic trying merge into slower, regular traffic caused the left-lane injury accident rate to soar at least 150 percent, according to the Texas findings.


The California study attempted to isolate likely causes for the higher accident rates. Because HOV facilities take up a significant amount of additional road space compared to general purpose lanes, the amount of shoulder space is often reduced. This created a source of conflict.
“Collision rates diminish with an increase in shoulder width, regardless of the type of access associated with the HOV lane,” the California study found.


In addition, the highest accident rates were found to be within 0.3 miles of an on-ramp or off-ramp for the limited access lanes. This suggests that concentrating the merge areas compounded the risk of accident caused by the radical speed differential between HOV and general purpose traffic. The Texas study found that only HOV lanes separated by permanent concrete barriers had a lower overall risk of accidents.


“The findings from this research show that the HOV facility with limited access offers no safety advantages over the one with a continuous access,” the California study concluded. “The combined collision rates of the HOV and its adjacent lane were higher for the HOV facility with limited access.”
Safety Evaluation of HOV Facilities in California »
http://www.thetruthaboutcars.com/lim...ase-accidents/
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Old 12-09-2008, 01:21 PM   #2
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that sounds reasonable. they should make the carpool lanes accessible at any time.
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Old 12-09-2008, 01:23 PM   #3
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So, once again, this proves that people don't know how to merge.
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Old 12-09-2008, 01:29 PM   #4
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So a big difference in speed between lanes increases accident rates? Well, duh, I think most people could have figured that out without some expensive 'study'.
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Old 12-09-2008, 01:34 PM   #5
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Originally Posted by DiscoGsus View Post
So, once again, this proves that people don't know how to merge.
There's no easy way to merge when your lane is stop and go and the lane you're merging with is full of traffic doing 55.

As an interesting side note, Berkeley home of the University of Ca did away with their HOV lane some time back because the negative traffic flow impact out weighed the benefits.
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Old 12-09-2008, 01:37 PM   #6
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Originally Posted by robertrinaustin View Post
There's no easy way to merge when your lane is stop and go and the lane you're merging with is full of traffic doing 55.
Sure there is. Thats why they have lanes to enter and exit the HOV sections. Which always get backed up because someone stops at the end of the lane right where it merges because they were afraid to floor it.

The always open ones are just bad ideas (mostly because people are always stupid about merging.) If you can't fit in a hole in traffic DON'T try.
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Old 12-09-2008, 02:12 PM   #7
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The Texas study found that only HOV lanes separated by permanent concrete barriers had a lower overall risk of accidents.
Boston's Zipper. Movable barrier only for rush hours.

--kC
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Old 12-09-2008, 02:51 PM   #8
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The solid fat white line seems to be way over 99% of the drivers on the road which also is a big part of the problem.

I like LA they have solid barriers in the areas where people cut the line persay.

SF bay Area we don't have any barriers even in the FastTrac only lanes for bridge approachs - I see it everytime I cross the Bay bridge some bone head on the far left decides its OK to cross 4+ lanes of Fasttrac traffic with little to zero reason to slow down so that they can get to the toll booth on the right side of the bridge! Wholly cow!! Batman!

Thin the herd :-)
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Old 12-09-2008, 04:36 PM   #9
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In Phoenix, the HOV lanes are only restricted in the morning and evening rush hour periods (IIRC, 6AM-9AM and 3PM-7PM M-F), and ingress/egress is allowed at all times. Otherwise, it functions as a regular lane that anyone can use. The fine is about $350, and I rarely see it being abused like I do in SoCal. I think the accident rate is higher where it's limited also because you have jackasses cutting in and out over the double-solids. A lot of drivers aren't expecting this since there is an assumption that they will only be merging in/out when they're supposed to. Here, you kinda have to be aware of it all the time.

-Mike
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Old 12-09-2008, 05:17 PM   #10
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The Socal carpool lanes are whacked.
I like how we can enter and leave the carpool lane anywhere up here
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Old 12-09-2008, 05:21 PM   #11
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Boston's Zipper. Movable barrier only for rush hours.

--kC

Yeah but Boston sucks to drive in, all day long.
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Old 12-10-2008, 07:15 AM   #12
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Yeah but Boston sucks to drive in, all day long.
But easier than your mother. Yeah. I went there.

Anyways, sure, it sucks. Not much you can do in cities, especially cities that have no grid system and room for expansion.

*shrug* But it's safe.

--kC
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Old 12-10-2008, 11:04 AM   #13
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Originally Posted by bemani View Post
The Socal carpool lanes are whacked.
I like how we can enter and leave the carpool lane anywhere up here
I'm pretty sure it's just LA and not all of socal. There weren't any barriers on the car pool lanes in SD when I lived there.
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Old 12-10-2008, 11:45 AM   #14
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Originally Posted by DiscoGsus View Post
Sure there is. Thats why they have lanes to enter and exit the HOV sections. Which always get backed up because someone stops at the end of the lane right where it merges because they were afraid to floor it.
maybe the car wouldnt move faster than a snail because its not in boost yet, and downshifting doesnt work because the next gear will be 1st and u know how hard it is to get in 1st while car is moving... all those lil 4-cyl cars with large turbos and "500 whp"...
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