Ft Worth TX: 133-Vehicle Accident on Icy Bridge in I-35W Toll Lanes

[motorola870]

This happens all the time in the more experienced snow driving north. So I do not understand how a overpass can cause a pile up. It was black ice, when the drivers saw the tail lights it was too late. They were already on the black ice and the grade heading south is down hill also.

I am more interested to see if the private company treated the road.

Well there were a lot of contributing factors. This section of road being completed about 3 years ago and there is even more questions to be asked such as why did TXDOT deem it necessary to double the length of the viaduct from the original configuration. I remember the construction.

[Bobby5280]

A lot of the motorists who were involved in the Fort Worth pile-up on I-35W were completely screwed before they realized it. They were driving along in what they thought were acceptable driving conditions, and likely pushing their speeds a bit in order to get ahead of the morning rush. They were driving fast in the express lanes and couldn't see what was ahead of them. Once the first couple motorists crashed out they were trapped on the main lanes thanks to the concrete Jersey barriers. If this pile up had happened on one of those really stupid single lane express lanes in the DFW area the pile up would have had a telescope effect with every car collapsing into each other like an old fashioned telescope tube. With the scale of this accident, 2 lanes of width didn't help much.

It's worth mentioning this Polar Vortex event has been all over the news for the past week. On Wednesday morning, a day prior to this pile-up in Fort Worth the freezing rain and black ice was wreaking havoc up here in Oklahoma. I-44 in Lawton was shut down for hours due to a truck jack-knifing on the Westbound lanes going into the Cache Road interchange. We had dozens of accidents all over town. I damned near did the splits slipping on my front porch as I stepped out the door to go to work! I think I-40 in Oklahoma City was shut down for a time due to a pile up there. There were hundreds of accidents all over the state, including a few fatal accidents. That should have given the folks down in the DFW area a clue of what was in store for them the next morning.

So I do not understand how a overpass can cause a pile up.

Bridges are the first roadways that cake-up with black ice. It's very likely that motorists going Southbound on I-35W were driving just fine in the express lanes right until they hit that long bridge going over Watauga Road and a rail line.

I-35W goes under the TX-183/28th Street exit and then immediately goes into a climb to get over the next street and that rail line. Freeway main lanes built at grade take longer to accumulate ice. There was a little bit of freezing rain that fell past midnight. But the significant freezing rain in that area didn't begin until about 6:00am Thursday morning -just 30 minutes prior to the pile-up.

I'm not sure that a digital sign would be enough to cure the bravado of Texas drivers, especially in the DFW area which, unlike the parts of the state north and west, generally doesn't experience slick conditions with anywhere near the regularity that would cause drivers to get an intuitive understanding of icy conditions being a big deal.

Few other cities can match drivers in DFW for Kamikaze-like speeding, swift lane changes and all sorts of other aggressive driving behaviors. New Orleans is pretty bad. But, yeah, it's very common for motorists in DFW to not take heed of road conditions. I've seen pile-ups happen in Dallas in the middle of Summer due to only rain-slicked pavement from an isolated shower.

[motorola870]

A lot of the motorists who were involved in the Fort Worth pile-up on I-35W were completely screwed before they realized it. They were driving along in what they thought were acceptable driving conditions, and likely pushing their speeds a bit in order to get ahead of the morning rush. They were driving fast in the express lanes and couldn't see what was ahead of them. Once the first couple motorists crashed out they were trapped on the main lanes thanks to the concrete Jersey barriers. If this pile up had happened on one of those really stupid single lane express lanes in the DFW area the pile up would have had a telescope effect with every car collapsing into each other like an old fashioned telescope tube. With the scale of this accident, 2 lanes of width didn't help much.

It's worth mentioning this Polar Vortex event has been all over the news for the past week. On Wednesday morning, a day prior to this pile-up in Fort Worth the freezing rain and black ice was wreaking havoc up here in Oklahoma. I-44 in Lawton was shut down for hours due to a truck jack-knifing on the Westbound lanes going into the Cache Road interchange. We had dozens of accidents all over town. I damned near did the splits slipping on my front porch as I stepped out the door to go to work! I think I-40 in Oklahoma City was shut down for a time due to a pile up there. There were hundreds of accidents all over the state, including a few fatal accidents. That should have given the folks down in the DFW area a clue of what was in store for them the next morning.

So I do not understand how a overpass can cause a pile up.

Bridges are the first roadways that cake-up with black ice. It's very likely that motorists going Southbound on I-35W were driving just fine in the express lanes right until they hit that long bridge going over Watauga Road and a rail line.

I-35W goes under the TX-183/28th Street exit and then immediately goes into a climb to get over the next street and that rail line. Freeway main lanes built at grade take longer to accumulate ice. There was a little bit of freezing rain that fell past midnight. But the significant freezing rain in that area didn't begin until about 6:00am Thursday morning -just 30 minutes prior to the pile-up.

I'm not sure that a digital sign would be enough to cure the bravado of Texas drivers, especially in the DFW area which, unlike the parts of the state north and west, generally doesn't experience slick conditions with anywhere near the regularity that would cause drivers to get an intuitive understanding of icy conditions being a big deal.

Few other cities can match drivers in DFW for Kamikaze-like speeding, swift lane changes and all sorts of other aggressive driving behaviors. New Orleans is pretty bad. But, yeah, it's very common for motorists in DFW to not take heed of road conditions. I've seen pile-ups happen in Dallas in the middle of Summer due to only rain-slicked pavement from an isolated shower.

Hopefully they make changes after the investigation the public's interest and not TEXPRESS including the possibility that 18 wheelers are prohibited from the lanes. Even before the crash the TEXPRESS system has some interesting choices on lane configurations. Such as left hand entrances and exits to the Express lanes. A lot of modern interchanges are eliminating left hand entrances and exits.

[hotdogPi]

So I do not understand how a overpass can cause a pile up.

Because northern drivers are used to snowy and icy conditions.

[rickmastfan67]

So I do not understand how a overpass can cause a pile up.

Because northern drivers are used to snowy and icy conditions.

That and my dad taught me & my brother that if an overpass could have ice on it, when you come up to it, let off your accelerator and coast over the bridge.  Once you're clear, then you can use your accelerator once again.  Of course, this doesn't work for those super long ones, but does for the majority of the super short ones on Interstates.

[kphoger]

So I do not understand how a overpass can cause a pile up.

Because northern drivers are used to snowy and icy conditions.

That and my dad taught me & my brother that if an overpass could have ice on it, when you come up to it, let off your accelerator and coast over the bridge.  Once you're clear, then you can use your accelerator once again.  Of course, this doesn't work for those super long ones, but does for the majority of the super short ones on Interstates.

Yes, and I've experienced it firsthand several times.  The worst part of I-135 going north here in Wichita is actually after it stops being the Canal Route and has become ground-level again.  It's just north of that point, where it goes over the railroad and Hydraulic/29th Street.  The reason it's worse is because, while the Canal Route itself is long and straight and level, that bridge has a slight curve and a slight incline.  Any ice there, and your drive wheels do funny things that they don't do on the Canal Route itself.

I also remember the time I was driving OK at 50-55 mph coming south down I-135, with some snow and ice but nothing out of the ordinary.  Bridges, curves, no problem, just slow down a little bit and all is well.  Then I came around the bend at 17th Street, where it becomes the Canal Route, and there were two wrecks on the viaduct, and my car spun out to 90 degrees before I could regain control.  Sometimes one bridge is fine but another is not.  That's just the way winter weather driving is.  People in this part of the country get a lot more experience learning these things than people in Dallas.

[J N Winkler]

My approach to driving on ice is informed by my background in physics.  The key is to keep net friction demand as low as possible.  Here are a few key facts:

*  Most tires start skidding when friction demand gets to about 65%-70% of gravitational acceleration on dry pavement.  Smooth ice reduces this friction capacity by at least a factor of 10.

*  Most sets of geometric design standards in use in advanced industrialized countries cap friction demand at about 25%.  This means that if you are moving at the design speed, the maximum lateral acceleration you should experience on the least forgiving curve allowable under the standards is about 25%.  Often (not always) the "hands-off" speed on curves--i.e., the speed at which there is no lateral acceleration at all and you can track through the curve without touching the steering wheel--is a consistent fraction (usually around 60%) of the design speed.  This often comes into play when negotiating curved ramps on structure, since going too slow can result in a vehicle skidding toward the inside of the curve since it does not have enough speed to oppose the superelevation.

*  Because we in the US are a weird, exceptionalist country, we use the same set of values for horizontal curve radii at a given design speed regardless of the maximum superelevation (e_max) used in a particular area.  8% is a pretty common value for e_max, but it can go as low as 4% in areas susceptible to frequent icing.  It helps to have at least an intuitive understanding of the superelevation provided in your area so you can choose your speed accordingly--lower maximum superelevation values translate to reduced tolerance for speeds above the hands-off speed.

*  The distance required to execute a given change in speed is proportional to the square of initial speed.  The relevant equation is v_f² = v_i² + 2ad.  This means that relatively modest reductions in your speed can greatly improve your ability to stop when traction is compromised.  But, as a practical matter, maintaining a margin of safety is a mixture of driving more slowly than usual and also leaving wider space cushions.  This is especially relevant for trips that occur during peak commute periods, when headways are typically shorter (important point:  it is not possible to achieve the usual maximum throughput of 2000 vehicles per lane per hour while maintaining the minimum two-second following distance that is usually recommended for safety).  When a storm comes through in the afternoon on a workday, it is not worth it to risk a car that costs a minimum of $20,000 to replace new just to get home at close to the usual time--I'd simply plan to leave later, even if it is hours later, and keep sleeping gear at the office during the winter.

[kphoger]

This often comes into play when negotiating curved ramps on structure, since going too slow can result in a vehicle skidding toward the inside of the curve since it does not have enough speed to oppose the superelevation.

This is also handy knowledge to have if you're navigating a muddy unpaved road and come upon a banked curve.  Too slow, and you'll find yourself at the bottom of the inside, unable to get back out again.

When a storm comes through in the afternoon on a workday, it is not worth it to risk a car that costs a minimum of $20,000 to replace new just to get home at close to the usual time--I'd simply plan to leave later, even if it is hours later, and keep sleeping gear at the office during the winter.

What do you do if the storm comes through in the morning?  Not go in?

[US 89]

So I do not understand how a overpass can cause a pile up.

Bridges are the first roadways that cake-up with black ice. It's very likely that motorists going Southbound on I-35W were driving just fine in the express lanes right until they hit that long bridge going over Watauga Road and a rail line.

The reason bridges ice first, by the way, is because they are exposed to the cold from both top and bottom. Regular roadways are only exposed to cold air from above, with (relatively) warmer ground below.

[Bobby5280]

We're getting into the worst of the winter storm here in Oklahoma now. The Turner Turnpike was shut down in both directions due to a pile-up earlier today.
https://www.koco.com/article/turner-turnpike-closed-in-both-directions-in-east-oklahoma-city/35502317#

I've measured 8 inches of snow so far in my back yard here in Lawton, and the temperature topped out at 8°F. We'll be below zero here by Monday morning and maybe close to -10°F by early Tuesday morning.

[kernals12]

If every single heat wave is held up as a reason to prevent climate change, can't we hold this mess up as a reason to encourage it?

[hotdogPi]

If every single heat wave is held up as a reason to prevent climate change, can't we hold this mess up as a reason to encourage it?

I realize full well that there's still plenty of time left before Spring, but...  It hasn't dropped below 16 degrees at all this year in Wichita.  If we don't have a decent cold snap, I have a feeling the bugs are going to be out in force when the weather warms up later.

Hopefully, that will come next week.

Houston's cold snap will get rid of the bugs this year.

[Scott5114]

If every single heat wave is held up as a reason to prevent climate change, can't we hold this mess up as a reason to encourage it?

No.

[kphoger]

If every single heat wave is held up as a reason to prevent climate change, can't we hold this mess up as a reason to encourage it?

Sure.

[CoreySamson]

Houston's cold snap will get rid of the bugs this year.

I'll let you know if that turns out to be the case. I hope so, but part of me thinks they'll stick around anyways. 

[Rothman]

If mosquitoes last the winter in the North, they will in the South...

[kernals12]

If mosquitoes last the winter in the North, they will in the South...

They... don't last the winter in the north?

[kphoger]

If mosquitoes last the winter in the North, they will in the South...

They aren't the only bugs.  Ant problems, for example, are a lot worse if we don't experience a good cold snap.

[mvak36]

Houston's cold snap will get rid of the bugs this year.

I'll let you know if that turns out to be the case. I hope so, but part of me thinks they'll stick around anyways. 

I would think they'd come back in the spring/summer. This weather might be enough to kill them off for a couple of months, but they'll be back.

[Bobby5280]

This evil cold spell isn't going to do squat about bugs in Oklahoma. We're still in the dead of winter. Maybe if we had a serious cold snap in April that would make a difference on the bug population. But not now.

[The Ghostbuster]

First there was the 133-Vehicle Accident in Fort Worth. Now the state has widespread power blackouts. I wonder what will happen to Texas next?

[jeffandnicole]

It appears this crash was caused by freezing drizzle. That is one of the hardest things to guard against. If it happened in a small localized area, it's almost impossible to get there at the appropriate time. When I do my snow work, I'm driving on a stretch of 10 miles of roadway. Doesn't matter how many times I go up and down, if I'm in one area and something occurs five miles away, it's going to take me at least 10 to 15 minutes to get to it most likely.

Brine is utilized to assist at the beginning of snow and ice. Once it gets wet it quickly loses its effectiveness. If it rained before the freezing drizzle occurred, it does no good as its washed away. If a freezing drizzle lasted for a period of time, the brine helped at first, then its effectiveness disminished quickly.

Salting roads before a storm generally doesn't help. Salt is like trash on a roadway. As traffic goes by it it gets swept off a dry Road. Salting a sriveway or parking lot may be okay, because traffic is moving at very slow speeds. Traffic on highways, at highway speeds, just blows it off.

And remember, this is Texas. Not only are motorists not used to such conditions, Texas doesn't have the large amounts of equipment needed on roadways for hazardous conditions. Even in other areas of the country that sees snow and ice often, the fact is trucks break down, and equipment malfunctions. I can be going down the road salting roadways, look back, and suddenly see that no salt is being spread. Now I have to figure out why that is, and once resolved, do I keep going or circle back? A lot of this work is manual or visual...I don't have stuff in my truck to notify me of every issue.

Treating roads for snow & ice is one of the most difficult things any transportation department has to face. Just a small area left untreated can cause issues like what we saw down in Texas. Also, when crews are plowing roads the plows are pushing against the immense amounts of snow, grinding against curbs, going over manhole covers that may not be flush with the ground, and utilizing equipment in freezing weather. It all makes fighting winter weather conditions an extremely difficult task.

I don't believe anyone else on these forums works with a transportation department in the area of plowing and salting roads. If you ever have the chance, try it for a season. You'll realize it's a very difficult job, especially with a demanding travelling public that feels roads should never be in less but perfect conditions at all times.

[motorola870]

It appears this crash was caused by freezing drizzle. That is one of the hardest things to guard against. If it happened in a small localized area, it's almost impossible to get there at the appropriate time. When I do my snow work, I'm driving on a stretch of 10 miles of roadway. Doesn't matter how many times I go up and down, if I'm in one area and something occurs five miles away, it's going to take me at least 10 to 15 minutes to get to it most likely.

Brine is utilized to assist at the beginning of snow and ice. Once it gets wet it quickly loses its effectiveness. If it rained before the freezing drizzle occurred, it does no good as its washed away. If a freezing drizzle lasted for a period of time, the brine helped at first, then its effectiveness disminished quickly.

Salting roads before a storm generally doesn't help. Salt is like trash on a roadway. As traffic goes by it it gets swept off a dry Road. Salting a sriveway or parking lot may be okay, because traffic is moving at very slow speeds. Traffic on highways, at highway speeds, just blows it off.

And remember, this is Texas. Not only are motorists not used to such conditions, Texas doesn't have the large amounts of equipment needed on roadways for hazardous conditions. Even in other areas of the country that sees snow and ice often, the fact is trucks break down, and equipment malfunctions. I can be going down the road salting roadways, look back, and suddenly see that no salt is being spread. Now I have to figure out why that is, and once resolved, do I keep going or circle back? A lot of this work is manual or visual...I don't have stuff in my truck to notify me of every issue.

Treating roads for snow & ice is one of the most difficult things any transportation department has to face. Just a small area left untreated can cause issues like what we saw down in Texas. Also, when crews are plowing roads the plows are pushing against the immense amounts of snow, grinding against curbs, going over manhole covers that may not be flush with the ground, and utilizing equipment in freezing weather. It all makes fighting winter weather conditions an extremely difficult task.

I don't believe anyone else on these forums works with a transportation department in the area of plowing and salting roads. If you ever have the chance, try it for a season. You'll realize it's a very difficult job, especially with a demanding travelling public that feels roads should never be in less but perfect conditions at all times.

Yes that is all true but locals have said for a while the lanes are not safe due to the fact they only have one shoulder and no exit in case of a wreck. Not to mention we have 1 travel lane wide express lanes on the eastern side of the metro. Don't be surprised if there is a push to ban big rigs off of the lanes. Its almost meme territory anyone you speak with talks about how they are literally sandwiched in between the jersey barriers.  I also wonder if Texpress will see a drop in usage after the wreck from drivers that are cautious and don't feel comfortable driving in such narrow lane configurations.

[kphoger]

Wouldn't the lack of Jersey barriers only have created the conditions for head-on collisions instead?

[ethanhopkin14]

I wonder if outfitting the express lanes with variable speed limits and lowering the limit for adverse weather conditions would mitigate risk.  I can see this being opposed by the express lane operator because of the associated costs of installation and operation, the prospect of poor compliance, and the repercussions for the pricing model.

Variable speed limits would be an excellent inclusion for the express lanes in Texas. I think they are posted at 75, which seems too high as a permanent, non-lowerable limit. 75 is likely acceptable most of the time, but certainly not all the time.

At the very least, variable limit signs (like those used by WSDOT) can display lane closed signs; this would have been helpful for traffic yesterday, as displaying multiple "X" symbols over the express lanes with accompanying VMS sign messaging (perhaps "incident ahead, prepare to stop") might have reduced the number of vehicles involved.

It's Texas. I'm not sure that a digital sign would be enough to cure the bravado of Texas drivers, especially in the DFW area which, unlike the parts of the state north and west, generally doesn't experience slick conditions with anywhere near the regularity that would cause drivers to get an intuitive understanding of icy conditions being a big deal.

In the Fort Worth incident, I tend to doubt the following will be fingered as proximate causes:
*  Barriers cutting off escape routes--It could be argued that the barriers actually helped, by keeping the pileup from overspilling into the general-purpose lanes.

It may not be factored in as an official contributing factor (if for no other reason than how common dual Jersey barrier designs are in Texas, and the amount of money it would take to convert them to anything else). However, it's hard to ignore them as someone who is not writing an official statement on the accident. It's not hard to imagine a driver in the situation of having successfully stopped before collision or only struck a glancing blow, but thanks to the barriers has no way to leave the scene before getting struck themselves by other vehicles that were not so lucky.

Yes everyone mentioning a lower speed limit would have help obviously hasn't driven this exact stretch of highway south of Ft. Worth where the speed limit is 60-65 mph and everyone is easily doing 90.  It's no joke at all, they are literally making you feel like you are sitting still when you are also speeding at 70.  I am not talking about 1 or 2 cars, but everyone on I-35W.