Early in the morning on Sunday, a Metro-North train derailed on the Hudson Line, immediately south of the junction with Amtrak’s Empire Connection: maps of the derailment area can be found on the BBC, while The LIRR Today has a map and a diagram with speed limits. Four cars overturned, and four people died while more than 70 others were injured. The train was going at 82 mph (132 km/h) through a tight curve at Spuyten Duyvil with a 30 mph limit; the speed limit on the straight segment before the curve is 75 mph according to Rich E. Green’s map, which may be a few years out of date, and 70 mph according to the first New York Times article about the derailment. The curve radius appears to be 230 meters on Google Earth, putting the lateral acceleration rate at 5.8 m/s^2, minus a small amount of superelevation (at most 0.8 m/s^2, or 125 mm, to perfectly match the centrifugal force at the curve’s speed limit, and likely lower); the cutting edge of tilting trains allows about 2 m/s^2 lateral acceleration (see PDF-p. 2 of this article about the Pendolino), or 300 mm cant deficiency.

Initial reports of a mechanical brake failure seem unfounded: a National Transportation Safety Board briefing mentions that the brakes had functioned properly on brake tests and at previous stops on the journey (starting at 00:40 in the video). The focus is now on human error: the NTSB refused to say this outright, but beginning at 03:00 in its briefing video it trumpets positive train control as something that “could have” prevented the accident. Rick Gallant, who led California’s rail regulatory agency at the time of the 2005 Glendale crash, is also quoted as saying positive train control “probably could have” prevented the accident on NBC. Moreover, the train driver is quoted as having told investigators “he had become dazed before the accident, suffering what his lawyer referred to as ‘highway hypnosis.'” Metro-North’s spokeswoman made the strongest statement: “if the accident was caused by speeding, positive train control would have stopped it.”

It is extremely likely that a robust train control system would have prevented the accident, as it is capable of slowing the train sufficiently before it reaches a speed restriction. The bulk of this post will be dedicated to talking about what train control systems can do. There’s a large array of acronyms, some of which mean different things in different countries, and one of which has two different meanings.

Broadly speaking, train control can prevent two types of dangerous driving: crashing into another train on the same track, and excessive speeding. If the system detects dangerous behavior, it will automatically stop or slow down the train. Driverless trains are based on robust enough systems that are so automated they no longer need the driver. The hard part is having an on-board system figure out whether the train is traveling too close to another train or too fast, which requires communication with the signaling system; automatically slowing the train down is comparatively easy. In nearly all cases, the signals are static and embedded in the track systems, but in a few, usually high-frequency subways rather than mainline rail, the system directly communicates with the train ahead on the same track (this is moving block signaling, or communication-based train control).

It is century-old technology to stop a train that is about to enter a segment of track too close to another train (“signal passed at danger,” or SPAD). A train’s steel wheels close an electric circuit that detects whether there is a train on a block of track, and this communicates to the signals entering this block of track to prohibit trains from proceeding; see diagrams in the moving-block signaling link, which also show how it works in the more common fixed-block setup. A situation that electrically insulates the train from the track is therefore extremely dangerous and may lead to line shutdowns for safety. Any system with the capability to stop a train in such a situation is called automatic train stop, or ATS. The 79 mph speed limit on nearly all passenger train lines in the US comes from a 1947 regulation by the Interstate Commerce Commission (which has since morphed into the FRA) requiring ATS or in-cab signaling at higher speed; the intention was to force the railroads to install ATS by threatening a crippling speed limit, not to actually reduce train speed.

It is much harder to enforce speed limits. ATS systems do not have to enforce speed limits: at Amagasaki, there was an ATS system that would have stopped a train running a stop signal (as it had earlier on the trip), but no protection from excessive speeding, which is what led to the crash. The signaling system needs to be able to communicate both permanent and temporary speed restrictions. It is nontrivial to maintain an up-to-date database of all speed restrictions on an on-board computer, or alternatively communicate many different speeds from wayside track signals to the train’s computer.

In 2008, the FRA mandated positive train control (PTC) as a result of the Chatsworth crash; PTC is a term that doesn’t exist outside North America, and refers to an automatic train control system capable of not just ATS but also enforcement of all speed restrictions. In Europe it is called automatic train protection, or ATP, and in Japan it is called automatic train control, or ATC. It is common in the US to do trackwork on one track of a multiple-track railroad and slap a temporary speed restriction on adjacent track, and enforcing such limits to protect wayside workers is specifically part of PTC.

Because the ATC system requires trainside equipment, a train that travels between different systems will need more equipment, raising its cost. In Europe, with its hodgepodge of national standards, some international trains require 7 different systems, raising locomotive costs by up to 60%. This led to the development of a unified Europe-wide standard, European Train Control System (ETCS), which combined with GSM radio for communication between lineside signals and the train is called European Rail Traffic Management System (ERTMS). The obligatory cost and schedule overruns of any IT project have plagued this system, and led to delays in installing train protection on some lines, which led to a fatal accident in Belgium. However, the agony of the ERTMS project has for the most part already passed, and now there is a wide variety of vendors manufacturing equipment to the specified standards, leading to widespread installations on new and upgraded lines outside Europe. As of September of 2013, ETCS is installed on 68,000 track-km and 9,000 vehicles worldwide.

Although ETCS is an emerging global standard (outside Japan, which has a vast system of domestic ATC with multiple domestic vendors), American agencies forced to install PTC have not used it. California HSR is planning to use ETCS, and Amtrak’s signaling system on much of the Northeast Corridor, Advanced Civil Speed Enforcement System (ACSES), with full implementation on the Northeast Corridor expected by this year, is similar to ETCS but not the same. Elsewhere in the US, systems have been bespoke (e.g. on Caltrain), or based on the lower-capacity systems used by the freight operators.

Metro-North does not have PTC. It has an ATS system that protects against SPAD, but can only enforce one speed limit, the maximum speed on the line (MAS). As the maximum speed on the outer Hudson Line is 90 mph, the system cannot enforce any lower speed, and so the train could travel at 82 mph even in 70 or 75 mph territory, let alone 30 mph territory. More modern systems can enforce several speed limits (e.g. the TGV’s TVM), and the most modern can enforce any speed limit, in 1 km/h or 1 mph increments.

Metro-North and the LIRR have been trying to wrangle their way out of the PTC mandate, saying it offers “marginal benefits”; a year and a half ago, the New York Post used the word “outrageous” to describe the PTC mandate, saying it would cost over a billion dollars and that the money could go to capacity improvements instead, such as station parking. Lobbying on behalf of Metro-North and the LIRR, Senator Charles Schumer made sure to amend a proposed Senate transportation bill to give the railroads waivers until 2018, so that they could devote resources to more rush hour capacity from the outer suburbs (such as Ronkonkoma) to Manhattan and fewer to safety. According to Siemens, the work will actually take until 2019, and Siemens says it “has developed PTC specifically for the North American market,” in other words built a bespoke system instead of ETCS. (ACSES was developed by Alstom.)

Because the systems developed for the US are based on the needs of American freight railroads and perhaps Amtrak, which do not need as much capacity in terms of trains per hour as the busiest commuter lines, they are much lower-capacity than those used in Europe. The LIRR and Metro-North have far busier mainline tracks than any other US commuter rail system with the exception of the inner part of New Jersey Transit, which is equipped with ACSES as part of the Northeast Corridor; to modify the system to their needs raises costs, as per the New York Post article. The MTA released the following statement (see also mirrors on Fox and CBS):

The MTA began work to install Positive Train Control on the Long Island Rail Road and Metro-North Railroad in 2009. To date, the MTA has budgeted nearly $600 million for elements of PTC installation, including a $428 million procurement last month for a system integrator. Full implementation is estimated to cost $900 million, and the MTA will make sure the appropriate funding is made to implement PTC on the most aggressive schedule possible. However, implementing PTC by the 2015 deadline will be very difficult for the MTA as well as for other commuter railroads, as the Federal Railroad Administration (FRA) and the Government Accountability Office (GAO) have both concluded.  Much of the technology is still under development and is untested and unproven for commuter railroads the size and complexity of Metro-North and LIRR, and all of the radio spectrum necessary to operate PTC has not been made available. The MTA will continue its efforts to install PTC as quickly as possible, and will continue to make all prudent and necessary investments to keep its network safe.

Of course, the technology is no longer under development or untested. Just ask the Belgians, the Swiss, the Chinese, the Saudi, or the Taiwanese. Older technologies meeting the definition of PTC exist practically everywhere on mainline trains in the European and Asian first world. Urban commuter lines in Tokyo such as the Tokaido Main Line and the Yamanote Line, each with more ridership than all North American commuter lines combined, are equipped with ATC. The RER A, with slightly less ridership than all North American commuter lines combined, has a train control system providing moving-block signaling capability on the central trunk. A Swiss mainline with 242 passenger and freight trains per day and minimum train spacing of 110 seconds at 200 km/h has ERTMS as its only ATP system, and Switzerland expects to fully equip its network with ERTMS by 2017.

Although the US mainline rail system is freight-primary, with different needs from those of Europe south of Scandinavia (e.g. critical trunk lines are thousands of kilometers long and lie in sparsely-populated territory), the same can’t be said of the Northeastern commuter rail lines, most of which only see a few daily freight trains and are dominated by tidal flows of commuter trains with high traffic density at rush hour. Rush hour traffic levels approaching 20 tph per track are routine, with 24-26 on the Northeast Corridor entering Penn Station from New Jersey. It is incompetent to try to adapt a system developed for long-distance low-cost freight railroads and ignore one developed for busy commuter lines just because it has an E for European in its name.

While most European countries have long implementation timelines coming from a large installed base of good but not top-line legacy signaling, countries with inferior systems sometimes choose to replace their entire signaling systems, as the passenger-primary parts of the US should. Denmark, whose intercity rail far lags that of most peer European countries, decided to replace its signaling system entirely with ERTMS. The projected cost is €3.2 billion, of which €2 billion is for ERTMS on the network, €400 million is for equipping the Copenhagen S-Bahn with CBTC, and €800 million is contingency; the total length of the system is 2,132 route-km and 3,240 track-km.

At a million euros per route-km, exclusive of contingency, Metro-North could install the system on all east-of-Hudson lines, except the New Haven Line, where Amtrak plans to install ACSES, for about $450 million, and the LIRR could install the system on its entire system (including parts currently without any signaling) for about $650 million. Denmark has about 700 trainsets and locomotives to install the system on, in addition to tracks; on the LIRR and Metro-North, those figures are about 150 each, although this assumes that trainsets would be permanently coupled, whereas today they run in married pairs, so that in an eight-car unit there are four cabs where only two are needed. If the LIRR and Metro-North agreed to treat trains as permanently-coupled sets, then the scope of the order would be about 40% of the size of the Danish fleet, consistent with a total cost of about a billion dollars.

This would also allow higher capacity than the current systems, which could squeeze more trains onto busy lines, so it wouldn’t be at the expense of capacity improvements. In particular, the LIRR could keep postponing the $1.5 billion Main Line third track to Hicksville project, and instead run trains on the currently double-track bidirectionally (today they run one-way at rush hour, to accommodate local and express service) using the very high frequency that ETCS permits. Another project, which Sen. Schumer thinks is more important than PTC, a $400 million plan to double-tracking the outer part of the Main Line from Farmingdale to Ronkonkoma, could also be postponed while still providing the necessary capacity.

Although both of the LIRR multi-tracking projects’ cost figures are enormous – the third track is about $100 million per kilometer, almost what a subway in suburbia should cost, and the outer second track is $15 million per km, more reasonable but still very high – adding tracks is in general more expensive than adding signals. IT procurement is expensive and prone to cost overruns, but once the initial system has been developed, the marginal cost of implementing it in new but similar environments is relatively low; ETCS would cost about the same on the LIRR and Metro-North as the MTA plans to spend on signaling, but provides better functionality as it’s compatible with their high traffic density. Organisation vor Elektronik vor Beton.

Of course the first step in the organization before electronics before concrete slogan is improving the state of the organization. In terms of safety, there may be scope for better training, but the train driver according to the NTSB has 10 years’ experience (start at 02:20 in the video) and based on his work schedule would have had enough time to get a full night’s sleep before his shift started (start at 07:25). Since there is no obvious organizational way to further improve safety, electronics is the next step, and this means installing a good PTC system in a timely manner.

However, in terms of cost, there is something to be done. While the MTA claims PTC is too expensive and provides little benefit, Metro-North spent $80 million a year on conductors’ salaries in 2010 (although it’s been going down, to about $65 million by 2012) and the LIRR spent another $95 million (in either 2010 or 2012), both numbers coming from the Empire Center’s SeeThroughNY. About six years’ worth of conductor salaries would pay for full PTC; future savings are free. The NTSB briefing said there were 4 conductors on the train (start at 09:15). The main duty of conductors is to sell, check, and punch tickets, an old-time rail practice that has been abolished in modern commuter railroads throughout the first world.

A commuter train needs between 0 and 1 conductor. Stephen Smith quotes Vukan Vuchic, a professor of transportation engineering at Penn who was involved in the implementation of SEPTA’s through-running in the 1980s, as saying that ticket-punching is “extremely obsolete” and “very 19th century.” A tour of any of the major urban commuter rail systems of Europe will reveal that a few, such as the Paris RER and the London systems, use turnstile, while most use proof-of-payment, in which roving teams of ticket inspectors only check a small proportion of the trains, slapping fines on people caught without a valid ticket. On American light rail lines, which are often similar in role to German commuter rail lines (especially tram-trains) except that they run on dedicated greenfield tracks, this is routine; this can and should extend to commuter mainlines. While the electronics is needed to handle safety, this organizational improvement would pay for the electronics.

Although the investigation seems to be going in a competent manner, the MTA’s position on the relevant issues in general does not come from a position of competence. It is not competent to have this many redundant employees but then cry poverty when it comes to avoiding crashes and derailments. And it is not competent to pretend that there is nothing in Europe or Japan worth using for American signaling systems. The US did not invent PTC – at most, it invented the term for what’s called ATP or ATC elsewhere. It shouldn’t act like it’s the only place in the world that uses it.