A Washington, DC, Metro train broke down for unknown reasons and another one jumped the tracks in another routine day for DC rail transit. The derailment was caused by a “heat kink” in the tracks, and Metro says it normally slows down trains during “extreme heat,” but hadn’t decided to do so in this heat wave.
Metal expands when it gets warm, and railroads used to leave gaps between the rails every 35 feet or so to allow for such expansion. But modern railroads weld the rails together to form a continuous ribbon that is prone to kinking at high temperatures. To deal with this, they use special allows that, they hope, won’t buckle in hot weather. The alloys used on Metro rails are good to temperatures up to 95 degrees, which DC exceeded for 11 days straight. Apparently, no one at Metro remembered to issue the slow orders.
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Metro’s solution is to replace the rails with ones capable of reaching temperatures of 105 degrees without kinking. In the meantime, “in the coming days,” Metro bureaucrats “plan to come up with new standards for heat restrictions that would be implemented immediately.” How can you implement them immediately when you are only planning to come up with them?
The derailment shut down the entire Green line for several hours, forcing passengers to find alternative transportation. It’s too bad Metro is still using obsolete and expensive trains when it could use vehicles on rubber tires that can go on ordinary pavement that would avoid problems like these.
it could use vehicles on rubber tires that can go on ordinary pavement that would avoid problems like these.
That can sit there idle when the pavement buckles in the heat. Or derechos bring down trees over the road. Or a sinkhole opens in the road. Or a water main breaks, flooding the road. Or or or. No one ‘best’ solution.
DS
Bingo!! I’ll invent wheels that turn so the rubber tire thingees can go another route around all that bad stuff.
That can sit there idle when the pavement buckles in the heat.
That happened in the same Maryland county (Prince George’s) as this “sun” kink in the rails on the Green Line. A section of pavement on U.S. 50 (John Hanson Highway) [which is an 8-lane freeway] buckled in the City of Bowie because of the heat.
The freeway remained open, temporary repairs were made within a few hours, and a permanent repair has already been made.
Or derechos bring down trees over the road.
There were some roads that were partly closed because of downed trees, but they were entirely cleared-away within about 24 hours (and sooner on primary system highways, which (in Maryland) are usually maintained by the state).
Another ding against robocars:
What happens when the computer fails to see a pothole that a human driver could see and avoid?
Potholes come in all shapes and sizes that computers would be hard pressed to have documented in their memory…
It’s a plus for automated cars.
Here’s the dings (Google the title as I don’t want to end up in the spam queue):
Swerving To Miss Pothole Leads To Crash In Tulsa
Driver swerves to miss pothole, strikes pedestrian
Half of drivers crash or have a near miss swerving to avoid potholes
Pothole swerve causes wreck in rural Newton County
Afghanistan veteran killed ‘swerving round pothole’ on British road
It goes on and on…
Theoretically, computers in automated cars could report the road hazard to a centralized database that computers in other automated cars could download. If autopilot failed to identify the pot hole and hit it instead of swerving into oncoming traffic, that is far preferable to human error and emotional overreaction.
Another ding against robocars:
What happens when the computer fails to see a pothole that a human driver could see and avoid?
Since the multi-fatal wreck on the Red Line at Fort Totten some years ago, all trains on the Washington Metrorail system have been operated in “manual” mode – Automatic Train Operation is not currently in use.
Here’s more good news from computer-assisted crash avoidance:
‘Intelligent Co-Pilot’ Keeps Cars From Crashing
New standards for heat restrictions. That’s a fancy way of finding excuses not to run Metro during certain times especially hot summer days. What’ll happen during very cold winters.
The Antiplanner wrote:
The derailment shut down the entire Green line for several hours, forcing passengers to find alternative transportation. It’s too bad Metro is still using obsolete and expensive trains when it could use vehicles on rubber tires that can go on ordinary pavement that would avoid problems like these.
It’s ironic, but this segment of the Green Line in Prince George’s County, Maryland was at one point in time planned to run next to a segment of I-95, much like the Orange Line runs in the median of I-66 in Arlington and Fairfax Counties, Virginia.
CPZ:
It’s ironic, but this segment of the Green Line in Prince George’s County, Maryland was at one point in time planned to run next to a segment of I-95
Not even close. I-95 was planned to go down the still existing PEPCO power line right of way from its junction with I-495 through Langley Park and Takoma Park and into the district. The Green Line is located along the CSX tracks 2.5 miles to the east.
http://en.wikipedia.org/wiki/Northeast_Freeway_(Washington,_D.C.)
Not even close. I-95 was planned to go down the still existing PEPCO power line right of way from its junction with I-495 through Langley Park and Takoma Park and into the district.
That was a later alternative that was discussed.
From the 1975 Final Environmental Impact Statement for Metrorail is this (emphasis added):
The sharing of transportation rights-of-way minimizes additional environmental impact attributable to Metro activities. Metro alignments such as the K and E Routes follow proposed highway rights-of-way, in these cases I-66 and I-95, respectively.
(The Green Line was known as the E Route during planning for the Metrorail system.)
The Green Line is located along the CSX tracks 2.5 miles to the east.
Incorrect. The Green Line crosses the CSX Metropolitan Subdivision at Fort Totten (near the site of the multi-fatal wreck in 2009), but the Red Line runs along (next to, then in the middle of) the CSX tracks from north of Union Station in D.C. to north of the Silver Spring Station in Montgomery County, Maryland.
The Green Line runs directly along the CSX Baltimore to Washington Main Line before going underground.
A short section of the Green line which is now underground near the DC boder was the portion planned to be near I 95. It would have been a half mile long segment. The Green Line has been planned to go to Greenbelt since 1967. I 95 has always been planned to follow the PEPCO right of way from its interchange with the Beltway up to the district line.
The segment with the track buckle is alongside CSX and nowhere near the PEPCO alignment.
Antiplanner:
What you wrote is simply embarrassing in terms of performing any basic investigation of the topic.
Metal expands when it gets warm,
Metal expands (mechanical strain) when it warms (thermal strain) IF IT IS UNCONSTRICTED. If the metal is constricted so as not to expand, the thermal strain is converted to mechanical stress, not mechanical strain.
railroads used to leave gaps between the rails every 35 feet or so to allow for such expansion.
Railroads left gaps in the rails because they had not perfected rail welding at that time, and rails were rolled in 39 ft. long sticks, not for thermal expansion. Today, they are rolled in 80 ft. or 240 ft. sticks, and they can be electric arc flash butt welded into any length desired.
But modern railroads weld the rails together to form a continuous ribbon that is prone to kinking at high temperatures.
Continuous welded rail (CWR) is not “prone to kinking at high temperatures” unless it has been improperly installed, or if it has been disturbed by maintenance activities and not readjusted. CWR is normally installed in the USA at 95 to 115 degrees. On the hottest days in our country, it will achieve a temperature of around 155-160 degrees while sitting in the sun. The rails are firmly connected to the ties by frictional fasteners or cutspikes, and the ties are heavy and sit in firmly compacted ballast stone which provides restraint on its ends through shoulders of ballast stone, and on the bottom and the sides of the ties through frictional resistence. This frictional resistence and dead weight is sufficient to restrain the rail up to a thermally induced stress equivalent to around 75 or 80 degrees.
To deal with this, they use special alloys
Railroad rail is a special alloy of steel, but that has to do with overall wear resistance and hardness to breaking and shattering. It has nothing to do with thermally induced stress and expansion, which is uniform in all steels.
that, they hope, won’t buckle in hot weather.
Railroads don’t rely on “hope” to make their tracks safe. Track safety with regard to the installation and maintenance of CWR is rigorously controlled by the FRA through its track regulations in 49 CFR Part 213, and railroad maintenance procedures. Track supervisors who fail in their duty face both company and federal discipline for the resulting accidents.
The alloys used on Metro rails are good to temperatures up to 95 degrees, which DC exceeded for 11 days straight.
Again, it has nothing to do with steel alloys.
Apparently, no one at Metro remembered to issue the slow orders.
Railroads have changed their practice in recent years to only issuing heat orders when ambient temperatures are over 98 degrees. Amtrak’s heat order restricts speed to 90 mph, which is 25 mph faster than the normal top speed on Metro. The slow orders again have nothing to do with the accident.
Metro’s solution is to replace the rails with ones capable of reaching temperatures of 105 degrees without kinking.
No, Metro’s solution is to properly stress the rails by heating them during re-installation to a surface temperature of 105 degrees. The issue on Metro, as I understand it, is that they have not kept up heat records of what temperature their CWR rails were installed at and when maintenance work disturbing the track was performed, if they ever even had such records and practices to begin with. As we have seen repeatedly at Washington Metro, the total lack of federal oversight of their safety practices has lead to repeated accidents and a black eye for the entire transit industry, even though the rest of the industry rarely suffers the problems which repeatedly plague Metro.
In the meantime, “in the coming days,†Metro bureaucrats “plan to come up with new standards for heat restrictions that would be implemented immediately.†How can you implement them immediately when you are only planning to come up with them?
They will implement it immediately by going out over the upcoming days and weeks on the surface parts of the system with unknown rail installation temperatures and thermally adjusting the rail by means of applied heat and mechanical stress.
It’s too bad Metro is still using obsolete and expensive trains when it could use vehicles on rubber tires that can go on ordinary pavement that would avoid problems like these.
Roadway pavement regularly buckles too. Google “roadway pavement buckle” and you come up with 294,000 articles concerning the topic. Recent ones include such titles as:
“I-39 pavement buckles; One of 30 lately statewide”
http://newstrib.com/main.asp?SectionID=2&SubSectionID=28&ArticleID=20630
“HEAT WAVE 2012: Road buckling continues, victim cautions drivers”
“It was the fifth section of pavement to blow up on Highway 29 in the past week. The Wisconsin Department of Transportation said the pavement buckles when slabs expand during hot weather, and push against each other, and that the state saw 17 pavement buckles on major highways on July 4 alone.”
http://www.weau.com/news/headlines/HEAT_WAVE_2012_Road_buckling_continues_victim_cautions_drivers_161513115.html?ref=115
Its worth noting Metro’s buckle was the single isolated incident reported on the railroads during the recent heatwave, and its causes were simply a failure of maintenance. As opposed to the hundreds of road buckles occurring with alarming frequency throughout the highway network, which represent a regular systemic failure in road design. I have pictures of pavement buckles where the concrete roadway shot upward as much as 3 to 5 feet. Your excitement may vary if this happens under your car.
Railroads have changed their practice in recent years to only issuing heat orders when ambient temperatures are over 98 degrees.
Why do the Virginia Railway Express and the Maryland Area Regional Commuter issue slow orders even if the temperatures are lower than 98° F?
Amtrak’s heat order restricts speed to 90 mph, which is 25 mph faster than the normal top speed on Metro.
Wrong. Metrorail trains may not exceed 59 MPH (even though, in theory, they are capable of 75 MPH).
The slow orders again have nothing to do with the accident.
How do you know that?
CPZ:
CSX has inadequate ballast sections and prior poor maintenance practices under previous management by John Snow. This has left a legacy of heat orders suffered by MARC and VRE commuters on CSX lines.
Adjacent MARC service on Amtrak and NS is not generally under heat orders because they have superior tack structure.
The Metro accident was caused by a track buckle, which occur from the rail under compressive stress. Heat orders are an attempt to limit train stresses on the track prone to buckling at that temperature. Washington Metro trains are very light, and their train speeds are generally not high enough for train forces to make much of a difference in the behavior of their track.
The actual cause, as noted already in their investigation, is the prior practice of an inadequate rail temperature of 85 degrees during construction. Most railroads use 95 t 115 degrees.