Heat Speed Restrictions

I know this has been covered before, more or less, but I was wondering how CSX figures out what heat speed restrictions to put on a particular track. Do they apply a general formula for all the track in a division, or perhaps they have to know how to deal with the exact characteristics of a particular piece of track. Anybody know?

jb

I think they use the following algorithm:

This article has everything you seek:

https://ggwash.org/view/31848/csx-explains-slower-train-speeds-in-heat-or-heavy-rain

CSX owns the tracks on MARC’s Brunswick and Camden Lines. CSX issues a heat order for operations between 1 pm and 7 pm if the predicted high temperature for the day is 90 degrees or higher, or if there is a large predicted change in temperature (e.g., 25 degrees or more), especially if the predicted high temperature is higher than 85 degrees. Large predicted changes in temperature are usually the reason for heat orders in the fall or spring.

If CSX issues a heat order, passenger trains must go 20 miles per hour below the maximum authorized speed, but not less than 40 miles per hour. Freight trains must go at least 10 miles per hour below the speed limit, but not less than 30 miles per hour. On the Brunswick and Camden Line tracks, under normal operations, the maximum authorized speed is 79 miles per hour for passenger trains and 60 miles per hour for freight trains.

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Ryan said:

This article has everything you seek:

https://ggwash.org/view/31848/csx-explains-slower-train-speeds-in-heat-or-heavy-rain

CSX owns the tracks on MARC’s Brunswick and Camden Lines. CSX issues a heat order for operations between 1 pm and 7 pm if the predicted high temperature for the day is 90 degrees or higher, or if there is a large predicted change in temperature (e.g., 25 degrees or more), especially if the predicted high temperature is higher than 85 degrees. Large predicted changes in temperature are usually the reason for heat orders in the fall or spring.

If CSX issues a heat order, passenger trains must go 20 miles per hour below the maximum authorized speed, but not less than 40 miles per hour. Freight trains must go at least 10 miles per hour below the speed limit, but not less than 30 miles per hour. On the Brunswick and Camden Line tracks, under normal operations, the maximum authorized speed is 79 miles per hour for passenger trains and 60 miles per hour for freight trains.

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I imagine that happens quite frequently in the Summer; the average high temperature in DC in July is just short of 90. National Airport reports an annual average of 36 days at or above 90 degrees. However, many suburban areas are generally cooler, so the heat restrictions are likely often only placed on part of a route.

MattW said:

I think they use the following algorithm:

If(Excuse.IsPlausible() AND Track.HostsPassengerTrains())
{
ApplyDelayingFactor();
}

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Amtrak has heat restrictions but the max speeds are somewhat higher as well as temperatures.

MattW said:

I think they use the following algorithm:

If(Excuse.IsPlausible() AND Track.HostsPassengerTrains())
{
ApplyDelayingFactor();
}

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LOL!!!

Heat restrictions are still put in place with the new rail technology like continuously-welded rail and concrete ties, correct?

daybeers said:

Heat restrictions are still put in place with the new rail technology like continuously-welded rail and concrete ties, correct?

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Yes, and are arguably more important on them, as the 2002 auto train derailment and the derailment of the capital limited in the same timeframe would suggest...

daybeers said:

Heat restrictions are still put in place with the new rail technology like continuously-welded rail and concrete ties, correct?

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From the linked article:

"Heat is a problem because modern railroads use continuous welded rail, rather than jointed track. Continuous welded rail is sections of rail that are 1/4-mile long, with the ends welded to the next section of rail. Unlike jointed track, there are no gaps between the sections of rail to accommodate expansion when the rail gets hot."

Not just welded rail. Durango and Silverton just had a derailment on stick rail due to a heat kink.

Ryan said:

daybeers said:

Heat restrictions are still put in place with the new rail technology like continuously-welded rail and concrete ties, correct?

Click to expand...

From the linked article:
"Heat is a problem because modern railroads use continuous welded rail, rather than jointed track. Continuous welded rail is sections of rail that are 1/4-mile long, with the ends welded to the next section of rail. Unlike jointed track, there are no gaps between the sections of rail to accommodate expansion when the rail gets hot."

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Sorry, I haven't had a chance to read the article yet, I just read the part that was quoted above.

west point said:

Not just welded rail. Durango and Silverton just had a derailment on stick rail due to a heat kink.

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Durango, CO has apparently been experiencing record high temperatures and long stretches of above average temperatures over the last several years.

Heh, this topic is suddenly making me wonder if there have been any speed restrictions through California and Arizona on the Sunset Limited route, as a result of the very hot temperatures that've been occurring as of late? And as many of us know, temporarily forced a few airports(mainly Phoenix, I forget if Las Vegas had to temporarily suspend arriving and departing planes) to not be able to have any plane arrivals/departures.

I thought the problem at Phoenix was specific to the CRJs and their design limitations. Why would all planes suddenly get affected at Las Vegas? Afterall most Boeing and Airbus models operate routinely in areas where temps go upto 120F and more, elsewhere in the world.

What can also happen is that a plane can operate, but with weight restrictions. The carrier can reduce weight by reducing passengers and luggage, carrying less freight, carrying less fuel, or a combination of those choices. I might not be able to carry enough fuel to make a long flight (stop over to refuel, ouch) or have to tell a bunch of passengers you can't fly, or leave a few containers or pallets of cargo from high paying shippers on the tarmac. Sometimes, it is just easier and more economically beneficial for the airline to say (cancelled) "see you tom'w". It can also result in changes in what runway length is required. So, PHX to LAX might work, but PHX to JFK (with the same aircraft) might be marginal or out, since I would have to carry way more fuel.

Yeah, tell me about it! I used to routines volunteer bump myself for compensation from Denver to Salt lake City flights in summertime before Denver International with its long runways was built. Almost without exception they asked for volunteers to meet weight restrictions for takeoff from Stapleton. I stayed in hotels around Stapleton on United's dime and funded many a vacation on many vouchers thus obtained back in the early 90s.

Actually, Stapleton's mains were pretty long, but it was something about the Rocky Mountains, and downtown Denver that made it extra scary. Altitude didn't/doesn't help, of course.

PVD said:

Actually, Stapleton's mains were pretty long, but it was something about the Rocky Mountains, and downtown Denver that made it extra scary. Altitude didn't/doesn't help, of course.

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Altitude together with high temperature is a bad combo. Makes the air even thinner and thus less able to bear weight at low speeds I suppose.

jis said:

PVD said:

Actually, Stapleton's mains were pretty long, but it was something about the Rocky Mountains, and downtown Denver that made it extra scary. Altitude didn't/doesn't help, of course.

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Altitude together with high temperature is a bad combo. Makes the air even thinner and thus less able to bear weight at low speeds I suppose.

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"All the more reason to "TAKE A TRAIN"

PVD said:

Actually, Stapleton's mains were pretty long, but it was something about the Rocky Mountains, and downtown Denver that made it extra scary. Altitude didn't/doesn't help, of course.

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From Stapleton, the normal takeoff was from 35 Left or Right, landings were on 26 Left or Right, so it was seldom taking off or landing directly to or from the mountains, west of the city.An exception was Rocky Mountain Airways, STOL DHC-7's...those birds would climb and descend almost like an elevator, and would takeoff direct on either 26 L or R...

Yeah, as I recall they always took off parallel to the mountains not towards them. But there still were some bizarre noise abatement stuff to contend with I suppose, which is a non issue at DIA.

Sometimes flying parallel to mountains is more troubling to passengers because they see them when they look out the window more prominently than when they climb out over them.

Railroad Bill said:

jis said:

PVD said:

Actually, Stapleton's mains were pretty long, but it was something about the Rocky Mountains, and downtown Denver that made it extra scary. Altitude didn't/doesn't help, of course.

Click to expand...

Altitude together with high temperature is a bad combo. Makes the air even thinner and thus less able to bear weight at low speeds I suppose.

Click to expand...

"All the more reason to "TAKE A TRAIN"

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Not really

Aircraft certification is very complicated.

1. First you have the structural weight limits of the aircraft. Then you have the total weight of the aircraft - any fuel weight limited. (max zero fuel weight ) Some conditions to carry max zero fuel weight cannot carry the max fuel.

2. The longest runway in the world may not use the above weights.

2a. Airplane wings do not know ground speed just true air speed (TAS). The true airspeed decreases with both higher temperature and higher altitude ( 29,92 is standard at sea level) So The higher the altitude and / or the higher the temperature the higher ground speed needed before getting same TAS for lift off or landing. You then get to tire limiting speed. As we all know all tire types are not created equal even on same aircraft. There are some higher speed tires made for various aircraft.

3. The next important item is what is known as second segment climb after gear retraction. Certification requires aircraft to be able to have a climb gradient of 1.3 with 1 engine inoperative.

3a. Total Engine thrust mainly affects how 2nd segment is met.

4. Early Jet transports were certified to what the weather service considered standard conditions. 15 C (59F), sea level 29.92. That included the Jet engines. So at 5000 feet standard was 5C (41F) 2992 that was corrected for the altitude.

As builders and users realized standard was too limiting so temperatures were increase to 30C (86F), then 40 C ( 194) Engines were rated thrust at standard and any increase of ALT or TEMP reduced thrust. Some engines sub models are now flat rated certified to 55C and higher altitudes. Think the middle east RB211-524s and CF6-80C2s. Also Air Force 1.