Link Light Rail has had some rough patches over the last month with a couple of major incidents occurring during peak commute times. The first was a Link-involved accident on MLK at the tail end of the Sept. 15 afternoon commute. A week later, Link was disrupted by a drive-by shooting in Columbia City that resulted in a crash near the tracks. These incidents are a timely reminder of the vulnerabilities (and dangers) of a rapid transit system that shares right-of-way with vehicle traffic. But how often is Link service disrupted? I’ll dig a bit into the data to shed some light on the statistics of Link interruptions.
My data source here is the Sound Transit alert feed which emails notices to subscribers when service interruptions occur. Service interruptions are anything causing delay or temporary closure, such as a mechanical problem with a train, power outage, blockage, or medical emergency. I’ve been subscribed to the alerts since December 2015, so I have about a year and nine months of service interruption records to analyze. In my experience, ST is pretty consistent with notices when an interruption happens, but it’s possible this dataset leaves out some incidents. Numbers reported here are, hence, minimum rates.
Overall, I count 76 separate Link service interruptions between Dec. 4, 2015 and Sept. 25, 2017. Given that there are about 660 days in the whole period, the high-level conclusion from the data is that you should expect a Link interruption about once every 9 days. That’s only an average, though, so sometimes there are more. What does the data look like? Below, I’ve graphed interruptions* by date and the duration of the service disruption in minutes.
I classified the interruptions into four groups (quartiles) based on their durations. The “Level 4” interruptions are generally an hour or more – and are the ones that daily Link riders may hold in their memories for some time – while “Level 1” events are 10 minutes or less. The median interruption is about 25 minutes.
It’s also interesting to just count the interruptions occurring in different time windows. In the chart below, I broke the observation period into 30 day intervals and plotted the number of interruptions in each interval.
The average number of interruptions per 30 days is between 3 and 4, with a notable peak of 8 interruptions around March 2016. Maybe some of these were glitches related to the U-Link opening? It can be tempting to claim a downward trend in the interruption rate with later dates, but the recent reductions are well within the natural variation of a statistical process** like this. In other words, there’s not enough data to claim that we will see fewer interruptions in the future.
Are interruptions more common on certain days of the week? Emphatically, yes. Service interruptions have overwhelmingly happened on weekdays. That’s not at all surprising given the larger numbers of both trains and cars during the work week. The chart below shows the breakdown by day-of-the-week.
There were zero Saturday interruptions in my dataset and only a couple of Sunday interruptions. Again, it is tempting to pose theories about why there were more interruptions later in the work week. However, I will again play the wet blanket card and say that the variation amongst the weekdays is well within the natural range. There’s not conclusive evidence here that Thursdays will see more interruptions than Tuesdays in the long term. What I can do is refine the interruption rate statement a bit: On any given weekday, there is about a 15% chance of a Link interruption.
What about time of day? I’ve got a chart for that too:
Evidently, the afternoon and early evening are more hazardous times to ride Link.
One final question: How does Link compare with other light rail systems when it comes to service interruptions? This is hard to answer because incident data is not generally available, but I do have some glimpses into other systems. For instance, The Oregonian reports that Portland’s MAX had around 300 interruptions in 2015. Considering interruptions per track mile, that puts the MAX rate in 2015 (~5 interrupt/t-m/yr) at more than double Link’s current rate (~2 interrupt/t-m/yr). MAX has a lot of operational complexity, including many at-grade crossings, so that may help explain such a large difference. On the other hand, Denver’s RTD system – which also has many at-grade crossings – seems to have an interruption rate that is closer to Link’s – with 88 interruptions in 220 days of 2016 over about 80 track miles (~1.9 interrupt/t-m/yr). It’s hard to know if these are apples-to-apples comparisons, but they at least provide some context for the numbers I’ve reported in this post.
[*] I’m missing duration estimates for 6 of the 76 interruptions. This is either a shortcoming of my interruption detector or due to a missing email from Sound Transit’s alert system.
[**] For those who care about such things, the Link interruption data exhibit the properties of a classic Poisson process when aggregated at 30-day intervals.
Regarding “Evidently, the afternoon and early evening are more hazardous times to ride Link.”
Anecdotally, as a bike commuter I feel like car traffic is generally crazier and drivers much more likely to behave erratically or aggressively in the afternoon commute. I’d guess it’s frustration at wanting to be home or stress from a long day of work. Given that many Link outages are related to car crashes in one form or another that doesn’t surprise me.
In the afternoon commute, drivers are in more of a rush because generally people care more about getting to their home/date/dinner/etc a few minutes faster than getting to work a few minutes faster. Also, in the afternoon commute, drivers are more likely to be on their phones talking to spouse, reading the texted grocery list for pick up on way home, FBing w friends on where they’re meeting for drinks, etc.
Traffic is heavier in general. I ride into work at 5am, and have never had an incident. I ride home at 4pm and it can be pretty crazy at times. I’m just glad I don’t have to work late and ride home during the “drunk hours” (9pm to 2am).
Mornings is just people going to work. Afternoons is people going home plus people running errands plus tourists plus people going to evening activities. When a bus is late or there’s a traffic bottleneck, the effects propogate to later in the day. So if a bus is often unreliable, it’s probably reliable in the early morning but gets thrown off schedule in the later morning or midday and never catches up, and if it’s a blockage that affects multiple buses then all their schedules get screwed up — in the later part of the day. Something similar is probably happening to Link.
Mornings the commute tends to be staggered and it’s broader, while afternoons people tend to leave at once. And the morning commuter as come off a nights sleep, while the afternoon commuter has come off the workday. I swear to g*d the IQ of the average afternoon driver is at least 30 points lower than the average morning driver.
Great post. I for one love this type of analysis, even with the limitations of the dataset you had to work with. Thanks for reporting on this.
Would it be possible for you to compile something similar on station issues such as the multiple elevator and escalator outages? These are troubling to me considering how new these facilities are.
What about location? Are pretty much all of these interruptions happening in the at-grade section on the rainier valley?
I think long term the ballard to tacoma line is going to be the worst. You have both the bridge crossing and the rainier valley segment, both of which can block the whole line. Realistically, this will also present a restriction on how frequently you can run trains.
The solution to the MLK issue is actually quite simple and affordable: block the line completely so that no cars can cross the tracks at any intersection, anywhere. It’s absolutely possible to “grade separate” the line, although I am willing to concede that this would hurt many car drivers’ feelings. On the plus side, maybe they’ll start taking THE TRAIN instead.
I should note that, of course, pedestrians and bikes will have street crossing opportunities.
Seriously, there’s, what 7 at-grade crossings right now? Just block them off and make the cars go around somewhere else. Driving habits would adjust accordingly.
Alternatively, social norming would be a great tool to use. Create a large countdown clock that resets on the 1st of year: “This intersection has 5 more collisions before it’s walled off and closed completely. DRIVE CAREFULLY.” If somebody pulls in front of a train, take a number away. When you reach zero, get out the jersey barriers and your intersection is permanently closed. Deal with it.
There’s an even cheaper solution: ?Photo?enforcement?.
It’s free.
It’s not just passenger vehicles using those streets but also all sorts of commercial traffic. I guess they can just “drive around” as well. You obviously haven’t considered the economic consequences of such a drastic proposal.
I wasn’t aware that commercial vehicles are less able to find alternative routes than private automobiles.
The economic impacts of intersection closure are probably marginal, and really, who cares? If the region’s premier transit system is knocked completely out of commission every 9 days, then perhaps it’s time to think about what THOSE economic impacts are.
Now, if we’re talking about the economic impacts of thousands and thousands of hurt car drivers’ feelings, then, well, you would probably be looking at a complete economic meltdown. Closing the intersections could, quite possibly, trigger a global hurt-feelings catastrophe, from which the sobbing, wailing, apoplectic car drivers might not ever recover.
There aren’t many “alternative routes”, that’s the point. The only arterials are MLK and Rainier. West of MLK it butts against a hillside after a couple blocks. East of Rainier it goes on further but those are all small residential streets. It’s a long narrow valley that’s oriented diagonally, and the arterials are diagonal to go along with it, but residential streets are straight north-south-east-west. So if you drive more than a few blocks you’ll run into one of those arterials. You could go stairstepping around them east-south-east-south but it’s inefficient and not all the streets go through. Maybe you could close the intersections on MLK like you said, but there was a big uproar recently when they eliminated left turns for Link, so this would be a second one, and I don’t know if it’s practically or politically feasible. But you’d be forcing somebody from the west at say Orcas Street to turn right and go all the way down to Rainier Beach and back to go further east, and somebody from the east would have to turn right and go up to Mt Baker and around. And Alaska Street is a highway feeder to I-5 and the West Seattle Freeway and it’s right in the middle; you probably can’t get it closed.
Jort.
“I wasn’t aware that commercial vehicles are less able to find alternative routes than private automobiles.”
This is a straw man argument.
Thanks for confirming my point that you have not thought through your proposal and all of its ramifications. Sorry, but I just can’t take your response with any level of seriousness.
@Tlsgwm, it isn’t a strawman at all; he’s responding to your specific point about “all sorts of commercial traffic.”
William C. Sorry, but it absolutely is. I never made the assertion he claimed. That’s a straw man argument.
I wasn’t aware that commercial vehicles are less able to find alternative routes than private automobiles.
He didn’t say that. He said that there would be large scale negative economic impact from closing off the crossing streets. Of course these drivers could figure out how to drive around.
But driving around costs money. In this case, lots of money.
Oh, and the idea that commercial vehicles couldn’t find alternative roues is (as was said) a straw man argument.
You can get a lot of the same benefits with the less drastic measure of crossing gates.
How expensive would it be to add crossing gates? Is there any reason not to have them?
Yeah, this is the best solution in the short term but I expect that section is gonna have to be fixed in the long term. Either with tunnel, trench, or elevated
Zachary B. I concur. Gates would work as an immediate fix but I think ultimately grade separation is going to be needed for a more permanent solution. How the agency does that without totally disrupting service in the meantime seems pretty complex.
A more permanent solution could certainly include permanently walling off the tracks so that no vehicles can cross them. This also has the benefit of not disrupting Link service in any way.
Also, on the plus side, it would take roughly one (1) day to do it, as all you have to put down are some jersey barriers. This would absolutely prevent vehicles from entering the track area.
The tracks will not be walled off because you would also prevent emergency vehicles from crossing and the fire and police departments will not allow that..
Also remember that the neighborhoods around MLK Way wanted the track underground but ST didn’t want to do that. The area residents and businesses didn’t want a street level track because they felt it would cut off neighborhoods from each other and now you are suggesting that the track be walled off so that nobody crosses them.
It isn’t going to happen.
Gates require flashing lights and the loud/obnoxious ding, ding, ding, ding.
Neighbors along the route (of which I am now one) were opposed and still are.
You can’t have gates without audible warnings? I can see why some bureaucrat might make that rule, but it doesn’t make sense in the real world: gates would be an upgrade to safety, even without anything else.
Groan; if this’s the case someone should put up signs saying “This collision courtesy of the FRA.”
You can have gates without audible warnings, but they don’t confer any of the regulatory benefits that full gates provide, and they’re far more likely to get broken through and require repair than gates with audible warnings..
is it possible to tunnel roads underneath existing tacks to make the hole system grade separate?
Or lower the track to a trench as I’ve advocated.
The cost of an at-grade alignment should include the slower speed, signal conflicts, collisions and deaths and downtime that are all caused by the at-grade alignment. If these were included in the cost comparision between at-grade and elevated or tunneled, then at-grads wouldn’t look so misleadingly less expensive.
That is an excellent idea!
There are some who would say that this would be expensive — but I say it would be simple to solve this with a per-use toll. Somewhere around $5 per crossing would definitely get it paid off in short order!
A $5 toll would make people to go around like Jort wants them to.
Mike. I totally agree with your post above. I too have advocated for grade separation along the light rail line. Sadly, ST took the “least expensive” path along this corridor. DKS Associates was the firm used for the traffic engineering part and their website indicates that Central Link entails 28 crossings with signals and 3 crossings with gates and signals. (Of course, they’re talking about the entire line and not just MLK Way.)
https://www.dksassociates.com/portfolio/sound-transit-seattle-central-link-light-rail-wa/
The cost of an at-grade alignment should include the slower speed, signal conflicts, collisions and deaths and downtime that are all caused by the at-grade alignment. If these were included in the cost comparison between at-grade and elevated or tunneled, then at-grades wouldn’t look so misleadingly less expensive.
Slower speed? My guess is there is a minimal difference. Even if this was underground, the train would spend very little time at maximum speed between stations, and even less as we start adding infill stations (like Graham).
Signal Conflicts? Yes, I would be very interested to see how often this occurs. It would factor into the speed difference. You could probably calculate the average speed, subtract out the dwell time, and then see how much time a train would save if the whole thing was underground. Again, my guess is it would be minimal.
Collisions and deaths? You would have to compare this to some sort of baseline, as collisions and deaths have occurred on this street long before Link was added.
Downtime? We still have no idea. We now know, at worst, that it really isn’t that bad. But this article — as good as it is — does not list the downtime caused by running the train on Rainier Valley versus the downtime caused by other factors (mechanical failures, shootings, Lysol, etc.).
Headway limitations — You failed to mention this, but it is by far the biggest weakness with running on the surface. We can’t run the trains as often as we would like. I could easily see running the trains every three minutes, which would be a much bigger time savings than the minimal increase in speed resulting from running underground.
Meanwhile, you would have to calculate the time *savings* that come from running on the surface. Every rider in Rainier Valley (except Mount Baker) has a short walk to the platform. If the tunnel was underground — even cut and cover — then the rider would have to spend extra time getting to the station. You would erase whatever time savings come from the faster speed.
So it all comes down to headways, really. Would Link be running every three minutes if it could? I doubt it. As Link expands, it might, but they haven’t build enough north end lines. There are essentially two lines coming from the south (this and East Link) and one to the north. As this expands (and Ballard and West Seattle is added) then it would be nice to run this every three minutes, but certainly not a necessity. Where is your turn back? SeaTac? Maybe, but hard to justify (that is pretty expensive to run a train that far). Even worse if you just run it all the way down to Tacoma (three minute trains to Tacoma sounds absurd). Rainier Beach could make some sense (assuming the area expands) but my guess is that even if it was possible to turn back in Rainier Valley, it would make more sense to just turn back after downtown (the current plan).
I seriously doubt it would be worth the money to “fix this”. This strikes me as yet another issue that people obsess about, while ignoring the really important stuff. ST has really screwed up a lot of things, but give them credit for making the frugal decision here. The worst thing about Rainier Valley rail is the Mount Baker station. Even if you accept that running on the surface is a bad choice, I think this would rank way down the list of bad choices ST has made. Put it this way, which would you rather have? A train running underground through Rainier Valley or
1) A station at First Hill
2) A station under 520 in Montlake
It’s not even close. It reminds of the silly hand wringing over the movable bridge in Ballard. Sure, in an ideal world we would have a very high bridge or an underground line. But either of those improvements pale in comparison to simply moving the Madison Street station up the street to First Hill. I feel like people are constantly worried about the wrong thing here. It really isn’t about the top speed of the trains, it is about the stations.
Yes. See BNSF main line in Tukwila near the Amtrak station or dozens of similar locations.
Problem is going to be intersections and driveway access.
I think it’s also time for some discussion, and probably a posting or two, how well LINK presently handles service recovery from a blockage. In every transit system, especially rail, ability to handle an emergency is as important as measures to avoid one.
The last load of passengers I carried through the Valley had rubber tires under their seats. So I really would like some words here from people who drive and supervise the trains. Floor’s yours.
Mark Dublin
Good point. Mistakes happen. How you deal with them often determines how reliable your system is.
Drivers are headed East-West. The train goes North-South. Blocking their path and forcing them on to the train won’t solve their transportation problem.
What everyone else said. This would be a dramatic change in the transportation system for Seattle. This isn’t like 15th West, where every major intersection has an overpass. Running on the surface there, while requiring cars to use those overpasses — essentially building a wall preventing cars from crossing — is quite reasonable. But not so in Rainier Valley.
There are no overpasses on MLK, and every major street is at ground level. You would force all of that traffic to basically “go around”, which means pushing an enormous amount of car traffic to Boeing Access Road and Rainier Avenue. It isn’t just cars that would be effected, but bus service as well. The 50 would split into at least two different bus routes, while the 106 and 107 would be forced down to Boeing Access road. That is just the direct effect. Cars would either plow through the residential streets (making a mockery of the Vision Zero plan until the city spent millions closing off streets, adding speed bumps and stop signs everywhere) or they would go around. Doing so would be a traffic nightmare on areas that are already congested (Boeing Access Road and the intersection of Rainier and MLK). This would greatly slow down the the buses that use those streets (and carry lots of riders) I’m all for creative ideas, but I’m afraid this one just wouldn’t work.
A road that doesn’t allow cross traffic is generally known as a freeway. This is what you’d essentially be turning the Link track into. I used to live at Melrose & Thomas and going to Eastlake or SLU meant walking down to Denny Way and back, or walking further up to Lakeview Blvd. South Seattle is lucky that I-5 goes along the side of a ridge next to an industrial district and not through the middle of Rainier Valley. This was one of the objections to the Thompson Expressway through the Arboretum and Central District and I don’t know how far south; it would have been like 15th Ave W. You can’t just put something like that willy-nilly in a residential neighborhood, not any more.If Link is to be grade-separated it will have to be elevated, in a trench, in a tunnel, or the cross arterials will have to go under it like Strander Blvd in Tukwila where it goes under the UL track. But note that that underpass takes a lot of space in the approach which may be too much to put around MLK.
I wish we had more information about the causes of the various “link-involved” accidents. I would be very interested to know what portion of those are caused by drivers running lights or ignoring left-turn restrictions.
Anecdotally, it’s a large percentage. I’ve witnessed a driver on MLK try to “beat the train” to make a u-turn against a red arrow…. and fail.
Those look suspiciously like ggplot graphs! :) Could you make the data set available for others to work with? I’m not able to find any public data sets covering interruptions on either the ST site or data.seattle.gov.
There are no trains in the 2am hour, so how could there be a service disruption then?
Extended hours service during New Year’s or some other special event?
I don’t ride Link on a daily basis, but the one service interruption I’ve experienced was not caused by the at-grade section. I was stuck in the tunnel between Westlake and University stations for an hour due to a mechanical failure on another train. I don’t know how this compares to disruptions caused by traffic collisions and public safety incidents in Rainier Valley, but it was extra inconvenient and stressful to be stuck in the tunnel, where I get no cell reception (I’m not on one of the carriers available down there). Since we weren’t at a station, we couldn’t get off, we had only difficult-to-hear announcements from the driver to tell us what was going on, and I couldn’t communicate with the outside world to tell them where I was.
I am curious now. Between Husky Stadium and International District, the tunnel is supposed to have service from the four major carriers – and by extension their MVNO/child carriers. What company do you use that isn’t using Verizon, AT&T, Sprint, or T-Mobile for their network?
Personally, I’m on Sprint and I’ve never been able to get a signal in any of the underground stations (besides one fluke each at Beacon and Capitol Hill), I always have to get on the DSTT wifi. And of course that isn’t present at UW or Capitol Hill, or in the tunnels between any of the stations.
I’m also on the Sprint network, and I’ve never gotten signal in the tunnel.
Most (all?) of the major carriers deny their MVNO’s access to 3rd party “roaming” towers. As the tunnel cells are operated by a third party (Mobilitie), it’s likely that only post-pay, 1st party customers can use them.
This is very interesting data, as far as it goes. But just to reiterate what many of said, it doesn’t go far enough.
In much of your essay, you mention the grade level crossings as being the cause of interruptions. Yet you offer no data to support that idea. There are plenty of subway systems that have very little in the way of grade level crossings (e. g. the New York subway system) yet have plenty of interruptions. Anecdotally, I can think of lots of examples of how our system was shut down, and it had nothing to do with Rainier Valley cars (there was a shooting, too much Lysol, mechanical failure, etc.).
Which is why I would love to see a plot like yours, but with it broken down by incident type. Just two types of dots; one for accidents on Rainier Valley, and another for everything else, would be very helpful. Maybe we would find that the bulk of the delays have nothing to do with Rainier Valley, but that several of the really big delays would have been prevented if we had built a tunnel.
“In much of your essay, you mention the grade level crossings as being the cause of interruptions.”
Huh? I think you’re making an inference that just isn’t supported. Perhaps you’re confusing some of the commentary with the OP’s piece. ??
I do agree with you in that it would be very interesting to see the data points presented by the parameter of “incident/delay cause”.
Just look at the opening paragraph. After mentioning a couple of interruptions caused by grade level running, he writes
These incidents are a timely reminder of the vulnerabilities (and dangers) of a rapid transit system that shares right-of-way with vehicle traffic.
He didn’t mention the Lysol outage, which would have made for a more interesting introduction. That is because it is than just an introduction, it is a premise, and he repeats it later on. He clearly implied that one of the major reasons we have outages is because the trains share right of way with vehicle traffic.
After digging into the data on outages, he then reiterates his claim:
MAX has a lot of operational complexity, including many at-grade crossings, so that may help explain such a large difference. … On the other hand, Denver’s RTD system – which also has many at-grade crossings – seems to have an interruption rate that is closer to Link’s
Again, the implication is that having lots of grade crossings is a major factor for outages, but provides no evidence to support his claim. It is quite likely that age and complexity have a much bigger effect, yet he never mentions the former, and only mentions the latter in passing.