Amtrak Cascades #501 south from Seattle derailed this morning, while crossing over I-5 in the vicinity of Mounts Road, west of Dupont. There are at least three casualties, many injuries, and some carriages are a total loss. Our thoughts are with survivors, and the families of everyone on board. No root cause has been established, although there are no grade crossings on this section of the line.

I-5 will likely be closed for hours, so avoid freeway travel in this area and expect major disruptions.

Seattle Times is actively covering this disaster.

Update 10:28: “Per the Pierce County Sheriff, if you had a loved one on Amtrak Cascades 501, there is a family reunification center now at the Dupont City Hall. Please go there, NOT to the scene. The Amtrak number to call if you have family members on the train is 1-800-523-9101.”

Update 2:02 PM: Statement from WSDOT

Update 12/19 9:47 AM: New York Times: “The National Transportation Safety Board said at a Monday night briefing that the train had been traveling more than twice the speed limit before it derailed, or at 80 miles per hour instead of the allowable 30 m.p.h.”

Also, a detailed summary from Sandy Johnston at the Itinerant Urbanist discussing PTC, Amtrak, and much more.

Update 12/19 11:02 AM: Zack Willhoite, Pierce Transit employee and frequent STB contributor (MrZ) and Jim Hamre of All Aboard Washington, died in the accident.  Our thoughts are with their families and the communities they helped to build.

116 Replies to “Casualties in Point Defiance Bypass Derailment”

  1. This is a terrible tragedy. As this was the inaugural run, I am assuming there were members of the transit advocacy community on board. Bracing for more news.

    1. Yes, Chris Karnes of @tacomatransit (advocacy) was onboard. Unharmed. His pictures from the scene have been much sought after by worldwide media and I heard him being interviewed on KOMO radio news as I was commuting to work.

    2. The NBC announcer may have been misinformed or misunderstood a statement that the trains run as fast as 79 mph on the bypass. He reported that “Amtrak had been location tracking the train at 81 miles per hour”.

      If so then overspeed is the cause. The curve on the north side of the freeway ending a couple of hundred yards before the second overpass cannot be designed for 79 mph, even for Talgos. It’s tight.

      I expect the bogie between the second and third cars derailed and was dragged to the safety rails on the second overpass and diverted off the trackway because the wheel 1passed on the other side of the safety couplet.

      I hope I’m wrong, but the alternative would likely be sabotage.

      1. According to the Kiro7 newsfeed, it’s believed that the train hit an object on the track before flying off, which could get a lot of people off the hook for this accident if that’s the case.

      2. We’ll see what the NTSB investigation says — maybe the engineer was simply speeding, since PTC was apparently not operational — but unfortunately this could be sabotage. Remember, the Sunset Limited was sabotaged back in 1995.

    3. ” As this was the inaugural run, I am assuming there were members of the transit advocacy community on board. Bracing for more news.”

      Seems like only yesterday Seattle Transit Bloggers were attacking Lakewood’s mayor for challenging the safety of this line.

    4. Aside from Chris, it sounds like Jim Hamre, Zack Wilhoitte (Bus Dude), and Warren Yee were on-board. I’ve heard Warren is okay but Jim and Zack are still missing. Hoping they’re in one of the local hospitals. :(

      1. I’m hearing Zack is no longer with us, according to a post in The Bus Lounge on Facebook. I hope I’m wrong :(

      2. This is so sad. I never knew Zack or Jim personally but knew plenty of people who did. I wouldn’t be surprised if we had crossed paths at some point when I was hanging in the Seattle transit crowd. It will be hard to get over this one.

  2. Looking at Google Earth, the track is straight crossing the freeway. Immediately prior to the overpass, however, there is a leftward (for a SB train) curve for several hundred feet.

    From north to south, the overpass crosses the SB freeway lanes, then a rather wide median (roughly 300′) then the NB lanes.

  3. Locomotive #181 (a GE P42, not one of the new Siemens locomotives) was leading the train. Probably not relevant to this tragedy but I wonder why they did not use a new locomotive for the inaugural.

    1. Thinking more about this, I forgot that these are push-pull trains normally. I don’t remember which direction the locomotive faces in normal operations. It is hard to see from the pictures whether there was another locomotive on the other end of the train or only a cab car.

      1. The older one appears to be the trailing engine. I thought the same thing at first, but I oriented myself after seeing more photos. I’m stunned this happened, as they’ve been doing testing for months.

      2. Cascades usually has the locomotive at the north end.

        Sounder has the locomotive as the south end. Except for one Everette train that is always the other way around for some (unknown to me) reason.

        For what its worth I love those old GE locomotives, they’re like something right out of Mad Max. Cascades trains seem to be a bit mix and match, I’ve occasionally seen them with BNSF locomotives.

        Very curious to find out what happened, wife and daughter use Cascades quite often for trips to Portland. My heart goes out to those affected by this, and to Amtrak which operates in a less than ideal environment.

    2. New pictures clear things up a bit. Looks like a new Siemens locomotive was on the train as well. Presumably in the front, which puts #181 in the rear.

      The Siemens locomotive is sitting in the middle of the freeway lanes as if it never made the curve and just continued straight ahead.

      1. That’s definitely what it looks like. It appears that the lead locomotive just went straight when it reached the curve. I’m not even seeing any marks to suggest that the locomotive rolled over.

      2. Pictures I saw make it look like the Siemens locomotive was leading and did not make the curve – went straight ahead. Several cars followed. Others seemed to have stayed on the track and fell to the left.

        If there isn’t a track defect or obstruction, overspeed seems probable

      3. It looks like the loco made it at least 500′ beyond the point of initial derailment. If it was going at 30mph, to cover this distance it would have to decelerate at around 0.9 m/s², or slightly less than the deceleration experienced during an emergency stop on the tracks. Traveling at 79 mph would give a deceleration of over 6m/s², which seems more consistent with the badly banged up front end of the train. This really does look like overspeed at first sight.

  4. What was the testing like on this new track? I assume they thoroughly tested this bypass, how did this happen? I was set to take the train to Portland in a couple weeks but I guess I’ll be taking Bolt Bus instead.

    1. I realize this is an active scene and my thoughts truly go out to the family and friends of this tragedy, it very easily could have been me given how often I ride this train.

      I’m scheduled to ride the train later this week and am wondering if I need to make other arrangements to Portland? And if so, are there even ways to get to Portland? I would assume all bus service is booked in the corridor.

      1. I’m scheduled on 501 tomorrow morning and Amtrak is showing the train as operating as scheduled, except that the route will be back on the coastline. There is at least one train cancelled tomorrow because the new schedule requires 7 all trainsets. Obviously, Amtrak is currently short one trainset.

      2. The thing is, even some bus service is going to have issues with the road closed.

        I’m guessing they will just convert the 6 am Portland to Eugene train to buses. It’s a bit slower that way, but ridership wise they really don’t need a train.

  5. I suspect the bypass will be closed until they can make sure there isn’t some fatal flaw in the tracks or something that caused or contributed to this.

      1. Public highways are far less stringently regulated, and have far higher margins for error than railroad lines, because they’re designed to be traversed by unfamiliar non-professionals. The bypass will absolutely be closed to passenger traffic until the NTSB figures out what happened.

      2. If the freeway had just opened and they suspected there might be something wrong in its structure or management, then yes. The AWV closes every year for seismic inspections, as do all the other freeways less often, and that’s just for preventative inspections.

      3. When I moved down here around five years ago, on same stretch of I-5 where it crosses the Nisqually River, a vehicle blew up in a crash and shut down the freeway for a whole day and most of the night.

        So my first several months here, “re-con” to find every possible highway and side-road to get out of Olympia to the north. Main reason I keep stressing need for some really solid regional transit here.

        But- and not kidding- so much for my easy fix of giving Olympia-Lacey a terminal. But kidding even less, present refugee flow out of Seattle is now seeing to it that if I don’t get across that river by five am, I’m stuck in traffic half an hour to my first usable exit at Dupont.

        Between Olympics and Cascades, there are alternative routes. Long but pretty and best of all, driving instead of being herded. But seeing sprawl revving up to turbine speed, these escape routes are temporary.

        “Takeaway” from this morning’s news? Whatever the official boundaries of ST’s service area were three years ago, good idea to consider Centralia southern border, Cascade foothills eastern, SR101, west, and Marysville north.

        Check your smart-phones and dashboard navigators. Edmonds-Kingston, Bainbridge Island, and Bremerton to SR’s 3 and 101. East-side, Auburn south on 161 and 162. SR7 probably already backed.

        Experience also good proof as to the real extent of the Central Puget Sound Region, and that for the last three years, Dupont is well inside its boundaries. And start to plan, politically- and service-, accordingly.

        Mark Dublin

    1. A closure for repairs and inspections seems certain. Likely there is damage to the track and railway bed. Potentially damage to signals or other trackside equipment. The overpass itself appears to be structurally intact, given it is still supporting part of the train, but there could be damage we can’t see from the pictures.

      The investigation will take some time too – NTSB will be on scene quickly but if coming from DC they won’t even be here until tonight.

      Unlike most motor vehicles, trains are huge and heavy, so when they crash there is a lot of potential for infrastructure damage.

  6. Horrible news. Had wanted to take the CS to Portland today to check out the new routing but decided to wait.
    Wasn’t there another accident near that location a couple a few months ago?

    1. There was a derailment of Train 506 on July 2 of this year. It was on the old tracks that the new bypass was replacing, near the Chamber’s Creek drawbridge. The determined cause of that derailment was that the engineer was running the train too fast for the crossing, which activated a derail switch.

      1. If by the rare chance, we find out that it is the same engineer as the July incident, and that yet again he was traveling too fast – the engineer should then face criminal charges and a very long prison sentence.

  7. I just recieved this via Facebook,

    Please boost the signal: Per the Pierce County Sheriff, if you had a loved one on Amtrak Cascades 501, there is a family reunification center now at the Dupont City Hall. Please go there, NOT to the scene.
    The Amtrak number to call if you have family members on the train is 1 800 523 9101.

    1. If that’s true, and it sounds like it is, it is a shame that we’ve been so damn slow to roll out PTC… at this point it is bordering on criminal negligence when the technology has been available for decades.

    2. Looking at the infrequency of the report, there is more than enough distance for the train to have slowed before the curve though. It’s not like this is was an actual speed recorder reading at the moment of derailment.

  8. Is it possible they never tested this connection between the bypass and the mainline? That’s the biggest thing that jumps out to me with this particular location. They’ve been testing the bypass track for a year, Sound Transit has been using the new connection in Tacoma for years but this connection in this location is the one part where there has never been a revenue service train.

    Also the media picking up on Dupont mayor claim this route is unsafe is BS. He was solely whining about grade crossings for motorists.

    1. That can’t be possible, right? They must have tested it. ST ran trains on the UW link for months without passengers before opening, and I assumed that was standard procedure for new passenger track.

      1. I know they’very been testing it and for a long time.

        I also unfortunately find something suspicious about this incident being the first run on a new line at this key location. Its known there was strong opposition to this line by some as evidenced by the Lakewood mayor.

    2. The train was a half to three-quarters of a mile from a trailing point turnout joining the Bypass to the easternmost main running track.

      The junction can have had no influence on this embarrassing tragedy.

  9. If this was BNSF’ fault, people would be clamoring for heads, arrests. etc. – and at least somebody would be fired. Why no outcry for the same here???

    1. Because we’re waiting to find out whose fault it is?

      If the reports about the train speeding at 81mph on 30mph track are true, then I think there should be serious consequences for the engineer. Similarly, if the track wasn’t adequately tested or signposted, then there should be serious consequences for the person negligent in that.

      1. … and if there was sabotage, trees placed on the tracks or the rails damaged deliberately (as with the Sunset Limited in 1995), then the saboteur needs to go to prison for murder.

      2. If the train’s engineers weren’t intimately familiar with this run, they would have to rely on speed zone markers. Are they intact and properly placed such that a train traveling 80 mph could slow down to 30 mph before the curve?

    2. Chill dude. This isn’t the middle ages—we don’t need to start prosecuting and executing people before we even know what went wrong. That kind of reaction is utterly worthless, other than creating some sort false sense of ‘having done something’.

    3. “Why no outcry for the same here???”

      Is this now a social requirement before the facts are known?

      As hard as it is to read even the armchair quarterbacking here on this blog, which is nothing compared to the misinformation and misunderstandings of the regular media and beyond (our favorite Ranting from our favorite Northwest comments section), at least enough commenters here understand the concept of having the facts drive the discussion.


  10. I have never, for a second, questioned my safety on a Cascades train. My prayers go out to everyone involved.

    1. This is the second derailment for Amtrak Cascades in less than 7 months. I am questioning their capabilities now – and for the time being, I plan on using alternatives for Portland Transportation.

  11. Incidentally, Bruce, does STB have the resources this morning to pass along first-hand traffic information from southern Sound? Headed west and then north toward SR’s 3 and 101. Will pass along info from coffee-stops along the way.


    1. This happened very close to the junction where the new bypass route meets the older main line. Assuming that Sound Transit owns every last inch of the bypass then this would have happened on ST track, but it’s also possible that BNSF retained ownership of a few miles of track leading up to the junction. Without specific, detailed knowledge of the agreement between ST and BNSF it may be difficult to say.

      1. At the very least, BNSF is the dispatching railroad for the signals and other train control. They have to have an integrated system in order to do Amtrak and Sounder.

        Thus, there may have been some confusion when emergency crews had to communicate with BNSF dispatch in Fort Worth, TX.

      1. Zero.

        Even if ST operated trains on this section (which they don’t), Sounder trains are operated by BNSF and maintained by Amtrak. Their only involvement in Sounder is owning some of the equipment and this section of line – which was purchased/leased from Tacoma Rail.

      2. ” literally zero involvement with Sound Transit, if any at all.”

        “The tracks that parallel I-5 will go into full-time use by Amtrak Cascades passenger trains in the fall. In preparation, tracks and signals have been undergoing testing at various speeds. Sound Transit, which owns the tracks and is managing the Point Defiance Bypass construction project for the Washington State Department of Transportation, conducted most of the testing in January and February.”

      1. Whole lotta nothing going on….

        “The tracks that parallel I-5 will go into full-time use by Amtrak Cascades passenger trains in the fall. In preparation, tracks and signals have been undergoing testing at various speeds. Sound Transit, which owns the tracks and is managing the Point Defiance Bypass construction project for the Washington State Department of Transportation, conducted most of the testing in January and February.”

      2. ST doesn’t have the necessary equipment to do that. It would have been ENSCO or someone with actual track equipment.

        Considering even its bus services are by contract operators, and that only several places in the country have equipment to do this type of inspection, the ST involvement was probably a signature.

    1. @Simon Said

      Reports indicate that it looks like it was an over speeding problem, not a track problem. Sound Transit doesn’t operate or fund Cascades at all. It looks like it was the fault of a bad engineer operating the train.

      1. Except for the rumors of an obstruction on the tracks. Given that and the suspicious timing, it’s important to check out the possibility of sabotage too.

  12. Thoughts and Prayers go out to the families of those involved in this tragic incident. Hoping those that were able to make it out safely have a quick recovery. And sorry for those who have lost loved ones.

  13. The Guardian says the track is “a high-speed rail route”. Did you know we had high-speed rail in the state, or that a British newspaper would consider it such? They must have quickly referenced some documents and misunderstood how trivially the term “high-speed” is used in the US and in the state. The article also calls Sound Transit “the Seattle transit agency”. And there’s an interesting tweet from our president.

    1. ” an interesting tweet from our president.”

      Authoritarians like trains, especially when they run on time.

      1. Well in fairness, this was literally the one place there was a major public investment in passenger rail.

      2. Yes. In case people have forgotten, this was a project funded by ARRA (stimulus plan) money.

        Also as a reminder, WA Congressinal delegation members Hastings, McMorris- Rodgers and Reichert all voted against the supplemental spending measure.

      3. It remains to be seen whether there will be a real infrastructure plan, or whether it will simply be fleecing the public for privatization schemes, and projects that companies were doing anyway. I wonder how many privatization schemes are pass-through corporations like real-estate deals and hedge-fund managers.

        P.S. Privatization schemes are how the Russian apparatchiks became the Russian oligarchs.

  14. Overhead shot from KIRO-TV helicopter clearly showed the speed limit sign very close to the point where the tracks change from concrete to wood ties — “T30 – P30” meaning a 30 mph speed for both Talgo and Passenger trains with conventional equipment. For the Sprinter engine to have traveled as far as it did down I5 the train speed would certainly had to been above 30. Also there are some reports that the speed was tracked as 81 mph just prior to the incident — if so it was 2 mph over absolute maximum for non auto controlled (PTC and other system) territory. Possible malfunction of the engine or some other mechanical issues or human failure?
    What is important right now, however, is caring for those affected and then learning what happened so it can be prevented in the future.

    1. I also see a ton of dirt and other debris around the locomotive. There’s no way a train travelling 30 MPH would have thrown that much dirt on the road.

    2. A call in to KIRO from a passenger that was on the train said that he was watching the GPS on his phone just prior to the accident. He related that they had just finished running along a stretch parallel to the freeway and had blown past the cars which is why he’d taken out his phone. He said the speed reported on his phone was 82mph. Another passenger commented on KCPQ that as they entered the curve the cars started to tilt and just “felt wrong” like the train was going way too fast for the curve.

      Hard to believe the road won’t be closed for days while the figure out how/where to move the locomotive and cars. They’ll also have to do a structural inspection of the bridge and almost certainly do some sort of stabilization work to make sure pieces of it aren’t falling down on traffic.

    3. What I dont get is how long they have been testing this route, I mean its insane the amount of time any rail line is tested in this country, how it then appears the 30 mph zone was a surprise to the engineer???? Surely the engineer must have had time in testing the new route??

      I mean I personally am surprised this new “high speed” stretch has a 30 mph zone especially after $180 million is spent to upgrade a former route, just as I’m surprised its all single track.

      1. Single track is fine because it is essentially a dedicated route for about 20 trains per day. Unless a train is way off schedule, they should never have to wait for the track to be clear.

      2. It probably would have cost another $50m to build a new, straighter overpass. Then again, with the $200m they’ll probably lose in the upcoming lawsuits, that would have been money well spent. Penny-wise, pound-foolish, as they say.

      3. How much would it have cost to turn on the PTC system before running the first revenue-service trains? Not a lot, I would guess. Or they should have delayed the launch. The more I am reading about the operational design (79mph to 30mph, downhill, in a short stretch) the more I am thinking that it was a huge mistake to rely on an engineer alone to safely operate this stretch of track (at least in the southbound direction).

      4. Driving that train, high on cocaine
        From a report issued just last November:

        Amtrak’s lack of a strong safety culture is at the heart of this accident,” investigator Mike Hoepf said.

        Amtrak said it would respond to the NTSB’s findings later on Tuesday.

        Toxicology reports showed that Carter, 61, had cocaine in his system and Adamovich, 59, tested positive for morphine, codeine and oxycodone. The train’s engineer, 47-year-old Alexander Hunter, tested positive for marijuana, according to the reports.

  15. Silver lining is how few passengers were on the train. Why was it so empty? 78 passengers, in seven cars? Each car can seat how many? 60?

    1. First time this train has operated on this schedule, so not that many people know about the new schedule yet.

      There were at least some news crews that got off in Tacoma. Hard to know how many seats went to them, leaving some seats empty until Olympia or Centralia.

      1. So this story illuminates two scandals.
        The horrific one is the apparent incompetence that has caused grievous harm to life and limb.
        The unspoken one is the oodles of federal dollars diverted from other priorities in order to fund a transit project for which there is precious little demand among the general public.

      2. What makes you say there’s “precious little demand”? That the literal first trip wasn’t packed full? That’s a bad metric. Look at how long it took I-5 to get jammed; look at how Link ridership’s been rising steadily.

        There are at least two scandals. The horrific one is as you say. The unspoken one is the rhetorical damage this will do over the next years to badly-needed transit projects across the country.

      3. Jane, I fully disagree. The first day of service came several days before peak holiday travel was happening, yet, when a lot of business operations were starting to wind down and slow down before the holidays. Moreover, there hasn’t been time for people to fully adjust to the schedule.

        An out-of-state friend rode the Cascades from Seattle to Portland just a few weeks ago. I used to work at a company with operations in Seattle, Vancouver WA, and Portland, and A LOT of travel took place between offices by myself, managers, technicians, human resources, and IT. Because I couldn’t get the timetables on Cascades to work out for meetings, I always had to drive, and so did most folks. I always checked the timetable though. With the expansion to service, I’m pretty sure that at least half of my trips could have been by Uber & Cascades, and the same would go for a fair number of my former peers. My company certainly wasn’t the only one. Business travelers require a degree of flexibility in scheduling, and the increase in Cascades service helps with that aspect. In the next two months, I have two planned leisure trips to Portland, and I believe one will be by train, although we haven’t bought tickets and are concerned it will be sold out. (This should help you understand that the demand is there.) You might also consider that folks from all over the state frequently travel to Olympia for government business with our state capitol. That includes oodles of people from Seattle, Everett, Tacoma, Bellingham, and Vancouver, and the Cascades provides that vital link to our lawmakers. Unrelated, we attempted to get a ticket for a family member to visit us during the holidays on the Empire Builder. It was sold out several days on either side of his desired trip, over a month in advance.

        Jane, the demand is there. No scandal related to that. Heavy traffic on I-5 from Portland to Seattle shows that the demand is there, as well.

      1. Source? Thank you.
        (May those we lost RIP. Condolences to their loved ones. And a speedy recovery to those who were injured.)

      2. Chris. Thank you. I had forgotten about the financial impact on the states from the Passenger Rail Investment and Improvement Act of 2008, which was ultimately passed as part of H.R.2095 – Railroad Safety Enhancement Act of 2008 (passed in the 110th Congress and signed by President GWB).

        Anyway, thanks for the link to the 2016 performance report.

  16. Does anyone know who is behind or where specifically their data is from? I’ve emailed their ‘contact us’ address but not heard back. Is there any data available directly from Amtrak on its train speeds? Trying to not pass along unreliable information to the public. Thanks!
    John Ryan, KUOW

    1. The data appears to come from Amtrak’s “Track your train” service. You can click on a train and it will show its last reported speed and bearing. I presume that website scapes the info off that page because as far I know, Amtrak does not provide an official feed of train locations.

  17. I was watching CNN this morning and they were stating that that route has 14 daily passenger trains on it. I did not think Amtrak had 14 daily trips? Or are they counting Sounder as well which does not run on that part of the track where the derailment took place.

    1. Seven trains each way (six Cascades and the Coast Starlight), each day, with the new schedule – so that’s 14 passenger trains.

      Of course that will go back to six each way, I assume, with the loss of this trainset. :(

      1. It’s possible Amtrak can use standard rail cars and still provide seven trips – albeit a longer ride than before.

      2. I can see them leasing standard cars from Amtrak for the short term. But if the damage to the trainset is too extensive they may want to start talking with California about those two Talgo trainsets they just leased (the ones originally built for Wisconsin).

    2. It looks like they will be running the new schedule along the old route between Seattle and Portland. They will sub in Superliner cars for Eugene-Portland for the time being.

      Long term, one has to wonder how they will maintain the new levels of service. I hope they can get PTC running and transition trains to the new route. If there are any hopes for ridership recovery, it is essential that they use the activation of PTC to launch the new route. Rail travel is already much safer than driving, and it will be even safer with PTC.

  18. Just got a notification on my phone that the NTSB is confirming the train was doing “80 in a 30 zone”

    1. yes, The NSTB (from Washington DC) had a press conference at around 11:30pm last night and she stated that the train was going 80mph at the time of the derailment where the speed limit on that part of the track is only 30mph.

  19. You’ve got a track previously carrying nothing but very small freights, grade-crossed by small rural roads. Crash happened where line switches into first actual railroad between there and the Puyallup River. Somebody check with the railroad about previous speed limit for the freights?

    Mark Dublin

  20. Since it appears that the train was going significantly overspeed due to engineer error, what would it take to bill the engineer for the cost of repairing the bridge and repairing or replacing the damaged locomotive and train cars?

    1. Or perhaps the train would not brake as intended. So many things we must not speculate about.

    2. That is speculation. The cause for the overspeed has not yet been determined.

      As for the question, it’s up to the courts and the result of the investigation. Based on past derailments in Philly and NYC it’s unlikely it will lead to what you suggest.

  21. Bruce,

    That Heavy dot com article appears to have been written by a bot and gave me all kinds of pop-up spam (from Amazon!).

    May I suggest you replace the link with the one from the Seattle Times?

  22. While it is possible that the overspeed condition leading to the train’s derailment was caused by the train’s engineer, another possible reason for overspeed that should be investigated is the SITRAC traction control software in the Siemens locomotive pulling the train. This software uses a sensorless field control algorithm for the traction motor(s) that has a known region of control instability at low speeds. When the locomotive slows down, as it normally would when approaching a curve with a known speed limit, the algorithm changes its mode of operation from forward traction to braking with regeneration. This change of algorithm operating quadrant causes the algorithm to pass through the region of known control instability. Algorithm simulations show that this instability can cause the algorithm to switch back into the forward traction mode on its own independently of the engineer’s command, causing unintended acceleration of the locomotive’s traction motor(s). The probability of this happening depends upon the time that the algorithm spends in the region of instability, which is dependent upon the train’s load and the time constants of the train’s braking system.

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