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.”
I’m not surprised. Anytime you have large relative speed differences between adjacent traffic lanes you are setting up the situation for nasty accidents. Getting into and out of the HOV lanes can be very treacherous.
Agreed. I hate limited access HOV lanes for this reason. The combination of drastic speed changes and a limited amount of road in which to enter/exit makes for great danger. I can’t tell you how many times I have crossed over solid lines in limited access HOV lanes because traffic was light and it was safer than attempting to cross over at the designated point in heavier traffic. HOV lanes really do need to be rethought.
«HOV lanes really do need to be rethought»
¿How about “done away with”?
These things, aside from dangerous, are discriminatory. We all pay gasoline taxes for highway construction, but somehow certain types of better taxpayers get their own exclusive lanes whereas the hoi-polloi get 2nd-class access.
I agree with vww12.
I love the HOV lane when I’m on my motorcycle, however I feel they are strongly ineffective in traffic for several reasons.
First of all they create a horrible bottleneck when they end, causing traffic in the left most normal lane to come to a screeching halt.
They cause the left most normal lane to come to a screeching halt (as well as all other lanes) any time a popular exit/entrance comes up.
Thirdly, they are not used enough (at least in Dallas). Is the gas saved by the cars that use the lane more than the gas wasted by the LOV that COULD be using that lane but instead sitting.. not moving.. in traffic; not only b/c of the lack of the use of the HOV lane but for the 2 reasons stated above?
^^i have to concur with above.
HOV are boondoogles that serve no real traffic easying purposes. Whenever those lanes atarts or end they created dangerous slowdowns that reverberate for miles.
Unfortunately in Texas it seems they want to now toll the access of these lanes, increasing even further the distingtion between the weel-offs and the common of the mortals.
It is the speed differential stupid!
When ever you have a big gap of speed between two travel lanes you are going to lots of accidents.
States that have split speed limits for trucks and cars on level ground also create this hazard.
It is just a barrel of fun on I-5 in Central CA when trucks doing 60ish (posted 55) and cars doing 80-90+ (posted 70).
Even better is how states practice social engineering when they allow favored technologies and/or the well connected to use the lane.
I find express lanes work better than HOV lanes. Just set off with concrete barriers two extra lanes that have no access to exit ramps for people traveling farther.
All these studies about how they don’t reduce congestion, they increase accidents, and yet the Illinois Tollway is planning to spend 500 million to add HOV lanes here in Chicagoland. Clearly its a money grab (anyone can go in, but based on congestion and occupants, certain cars will pay more).
That tollway commission is about as corrupt as it gets. Though with our governor now going to jail (de facto dictator to the spinless tollway members) maybe this stupid idea can follow him to prison as well.
In TX, they generally go with fully separated HOV networks (like Houston’s) which are incredibly expensive compared to just doing what saner cities/states have done and building good passenger rail (light rail). You could build elevated light rail, in fact, for a comparable cost to Houston’s HOV network, and that’s the type we generally consider too expensive to discuss outside outliers like Honolulu.
There is a difference between the Lexus lanes (pay to get on HOV) and regular HOV (2+ passengers, maybe hybrids, etc).
Lexus lanes are pretty much unforgivable.
Regular HOV lanes I don’t have a beef with, but I don’t use them much. The highway nearest me is entirely HOV in the rush hours, which strikes me as a great idea. But you don’t have a speed differential there.
Does the Federal goverment provide additional highway money for carpool lanes – or is this strictly aa state budget issue?
I would guess that if the feds pay, the states put them in, thinking that some lane is better than no lane.
Toll HOV lanes, IMHO, are stupid, and seem morally wrong. Public infrastructure should be accessed by the public, not just those who pay for it.
Lexus lanes are quite forgivable – for one thing, gas taxes do NOT pay for the cost of highway (not even close – the shortfall is made up for by the fact that you pay a lot of gas taxes while driving on roads that never get funded that way, plus a healthy dollop of ‘contributions’ from local and state general funds).
For another, there is nothing wrong with using pricing to clear a market – it’s called capitalism. The alternative, what many here seem to prefer, used to be decried as communism – clearing markets via long queues.
turbobeetle : Thirdly, they are not used enough (at least in Dallas).
In the real world, other traffic combined with the limited entrance and exit areas makes them difficult to use. They just don’t seem worth the hassle and most of the time I (and my carpool buddies) don’t use them.
At the federal level, the law is specifically written so that federal gas taxes will not pay the full cost of a project. That portion is sent to the Federal Highway Trust Fund, which is then used on federal road projects and mass transit systems. Changes made to the law in the 1980s specifically require that a certain portion of federal fuel and motor vehicle products be spent on mass transit systems and “other” projects (bicycle paths, for example).
States are expected to kick in their share (80 percent, if I recall correctly) even on federal road projects, and how they raise that share is up to them. Every state has a gasoline tax, which it is free to use on road projects. The big problem is that many states divert these revenues to other sources. I recall reading on this site a link provided to supposedly show that Texas’s state gas taxes don’t cover the cost of roads in Texas. Considering that 1/3 of gas tax revenues are being diverted for education spending, we need to first question why gas taxes are being diverted to other uses, instead of criticizing them for not covering all road construction and maintenance costs.
And considering that urban drivers drive less than suburban and rural drivers, and thus pay less in gasoline taxes, it stands to reason that roads used mostly by suburban and urban drivers should get the lion’s share of attention (and tax money).
geeber, we’ve had this discussion before, and you’re dead wrong. The right way to look at this is proportionally – if the urban driver generates $500/year in gas taxes but only $100 goes to roads he gets to drive on, while the suburban driver generates $1000/year in gas taxes, but $1200/year goes to roads he gets to drive on, then the suburban driver is getting subsidized – period.
The ‘diversions’ of state gas taxes pale in comparison to the amount kicked in from gas taxes generated while driving on non-gas-tax-funded roadways and general funds. For instance, this recent TXDOT study:
http://theoverheadwire.blogspot.com/2008/07/replay-truth-about-roads-6107.html
(can’t find the original now)
shows that drivers would be expected to generate only a small fraction of the funds necessary to maintain that one roadway while driving on that one roadway.
Please cut this “suburban drivers drive more” nonsense out. It’s not remotely relevant to the question.
«The big problem is that many states divert these revenues to other sources.»
Not only states: in point of fact, the Federal Government diverts almost 40% of your 18¢/gal federal gasoline taxes to stuff unrelated to highways, such as rail, subways, etc. They call it “flexing” (21%) and “Mass Transit Account” (16%).
Source of the two slides below: the Federal Transit Administration
Yes, and the total of all those ‘diversions’ pales in comparison to the amount of gas taxes collected on roads which never see a dime of gas-tax-funding, and the amount of local, county, and state property and sales and income taxes spent on roadways.
Not even in the same ballpark.