Fix DeKalb Avenue
In New York, there are two dedicated subway tracks on the Manhattan Bridge offering a bypass of Lower Manhattan. Between DeKalb Avenue in Brooklyn and Canal Street in Chinatown in Manhattan, Q trains run nonstop for 3.5 km, while the R train goes the long way, taking 5.5 km and making 2 intermediate stops in Downtown Brooklyn and 4 in Lower Manhattan. The N skips DeKalb Avenue, with a 4.5 km nonstop segment between Canal Street and the Atlantic/Pacific/Barclays station complex.
The Q and N should be immense time savers. Instead, the Q does the trip in 8 minutes and the N in 10, both of which average 26-27 km/h. The subway’s overall average speed, weighed down by local trains stopping every 700 meters, is 29 km/h. The Q and N are still time savers, though, because the R does the 5.5 km in 18 minutes, an average speed of 16 km/h – far less than the systemwide average, and even less than the slowest Paris Metro line, Line 4 with its 500-meter interstations and 20 km/h average speed. Between DeKalb and Pacific, about 800 meters, the R takes 3 minutes. Unfortunately, New York City Transit is not taking any measures that would fix this, and when I asked about one possibility, I got excuses.
There are two reasons why this part of the subway is so slow. The first is something called signal timers. Timers are devices installed at frequent intervals on long interstations, such as the bridges and tunnels connecting Manhattan with Brooklyn and Queens, limiting train speed. These timers have always been around, but after fatal accidents in the 1990s, New York City Transit tightened them, reducing speed further; for some more background, see my Vox piece from last summer. The timers are more safety theater than safety. The biggest conclusion I reached from looking at the accident postmortem on the NTSB and some NYCT information was “make sure your trains’ brakes work as intended”; NYCT derated the trains’ service and emergency braking rates later in the 90s, which marginally reduces maintenance costs but is bad for safety and brutal for train speed.
The second reason is the switches at DeKalb Avenue. DeKalb is a six-track station, with four tracks feeding the Manhattan Bridge and two feeding the tunnel through Lower Manhattan. The two tunnel tracks then continue to the south as local tracks on the Fourth Avenue Line, carrying the R; this is the least used of all subway trunk lines into Manhattan, because the detour and low speed make it useless for most Midtown-bound passengers. The four bridge tracks include two express tracks at DeKalb going to the Brighton Line, and two super-express tracks skipping DeKalb continuing to the south as express Fourth Avenue tracks. Today, there is a splitting and recombining of branches. The B and D run together from Sixth Avenue to the Manhattan Bridge, and the N and Q run together from Broadway, but just north of DeKalb they recombine as B and Q running to Brighton, and D and N running super-express down Fourth Avenue.
This recombination at DeKalb slows down trains considerably, in two ways. First, the interlocking is complex. You can see it on this map on NYCSubway.org; in addition to splitting and recombining the B, D, N, and Q, it also has a non-revenue connection allowing R trains to serve the Brighton Line. Trains on diverging turnouts go at glacial speeds. And second, trains from four lines influence one another’s schedules, and delays propagate. Supervising train movements is thus difficult, and control center has to have a camera watching the trains enter the interlocking to ensure they adhere to schedule; timetables have to take the resulting delays into account.
When I first complained about reverse-branching in New York, I talked about capacity limits imposed by having more trunk lines than branches, a situation that is still to some extent true going north and east of Midtown. At DeKalb, there are six tracks going in and six going out, but the recombination makes things slower, and should be removed. NYCT should make a decision between having B and D trains run on the Brighton Line and the N and Q on Fourth Avenue, or the reverse. The interlocking permits either option, with entirely grade-separated junctions, allowing the trains on the two lines to no longer interfere with each other’s operations.
I in fact asked NYCT about it by proxy. NYCT dismissed the idea, on the grounds that transfer volumes between the B/D and N/Q would be too big. At Atlantic/Pacific, the Pacific side has a cross-platform transfer between the local R and express D/N, but going between the Pacific side and the Atlantic side (the B/Q, and separately the 2/3/4/5) involves a lot of walking. NYCT believes that passengers would flood the corridors looking for a train to their preferred destination, and the transfer volumes would require trains to have long dwell times. NYCT said nothing about whether the overall speed would actually fall, but I believe that based on the large transfer volumes NYCT predicts, passenger trip times (including transfer times) would rise. The only problem: I don’t believe NYCT’s prediction is true at all.
The B and D trains go express up Sixth Avenue, making stops at Grand Street in Chinatown, Broadway-Lafayette on Houston Street, West Fourth Street in the Village, and Herald Square. The N and Q trains go express up Broadway, serving Canal Street in Chinatown, Union Square, and Herald Square. North of Herald Square the two lines are never more than one long block apart until they leave Midtown. Passengers going toward Midtown are unlikely to have strong opinions about which of the two lines they would prefer.
Passengers going to destinations between Manhattan Bridge and Midtown might register stronger preferences. Union Square is the fourth busiest subway station in New York, and is quite far from the B and D. The closest alternative using the B and D is to change cross-platform to the M or F at West Fourth, and get off at 14th Street and Sixth Avenue, two long blocks from Union Square. Three more stations are potential concerns: Canal Street ranks 18th, West Fourth ranks 21st, and Broadway-Lafayette ranks 25th. Getting to Broadway-Lafayette from the N or Q is easy: the station and Canal Street are both on the 6, and passengers can transfer to the 6 at Canal.
West Fourth and Canal remain concerns, but they are not huge ones; they are secondary destinations. Canal is only a major destination for Chinese-New Yorkers, and in Brooklyn they cluster in Sunset Park along Fourth Avenue, suggesting that the Fourth Avenue express tracks should carry the N and Q and the Brighton tracks should carry the B and D. The urban geography of Chinese-New Yorkers is changing due to the combination of fast immigration and fast integration and migration to the suburbs, but this is a service decision, not an infrastructure investment; it can be reversed if demographics change.
Moreover, as a destination, West Fourth is predominantly used for NYU. The Village is a dense residential neighborhood, and West Fourth allows its residents to easily reach Lower Manhattan, Downtown Brooklyn, and two different four-track trunk lines through Midtown. But it has few jobs, outside NYU, which lies mostly between Sixth Avenue and Broadway. Union Square can adequately serve people going toward NYU, and stations on the R and 6 to the south can serve people going to NYU even better. The one problem is that the transfer between the R and the N/Q at Canal Street is not cross-platform; the cross-platform transfers start at Union Square. But with coverage of multiple stations walkable to NYU, the loss of the one-seat ride to West Fourth is not fatal. Even the transfer to the A, C, and E trains at West Fourth has alternative options: passengers from the N or Q going to the E can transfer to the F or M at Herald Square and reach the same stations, and passengers going to the A or C can transfer to the 1 at Times Square and to the A or C at Columbus Circle, both of which transfers are not much harder than climbing two flights of stairs at West Fourth.
With so many options, not many riders would be connecting at Atlantic/Pacific, and trains could keep dwell times short. If anything, dwell times might be shorter, because missing a train would be less fatal: the next train on the same track would serve the same destinations in Midtown, so riders would only need to wait about 3 minutes at rush hour, and 5 minutes off-peak. The gain in speed would be substantial, with the interlocking imposing fewer operational constraints.
NYCT might need to slightly rework the switches, to make sure the chosen matching of the lines in Manhattan and Brooklyn takes the straight and not the diverging direction at the turnouts; typically, the straight direction imposes no speed limit (up to full line speed on high-speed rail lines), but the diverging direction is slow. A matching in which the B and D go on Brighton and the N and Q on Fourth Avenue express to my understanding already involves only one diverging move, if I am reading the track map linked on NYCSubway.org correctly. At the same time, NYCT could fix the switches leading to the R: there was through-service from the Brighton Line to the tunnel tracks the R uses today, but there no longer is, so this out-of-service connection should get diverging and not straight moves. But even with the R, the capital investment involved is minimal.
I do not know the potential travel time gains between DeKalb and Canal Street (or Grand Street) with no timers or reverse-branching. With straight tracks across Manhattan Bridge, and wide curves toward Grand Street, 3.5-minute trips are aspirational, 4-minute trips are still possible, and 5-minute trips should be easy. From Pacific Street, add one more minute, corresponding to cruising at 50 km/h, a speed limit the subway routinely attains even on local tracks. This saves passengers from DeKalb about 4 minutes, and passengers from Pacific about 5. The average trip across the system is about 21 minutes, and the average delay (“excess journey time“) is 3 minutes. The saving would be immense, and contribute to both more casual ridership between Brooklyn and Manhattan, and lower operating costs coming from faster trips.
NYCT should not make excuses for this. The timers may have been originally justified as a safety improvement, but reducing train braking rates had the opposite effect. And, uniquely among the various reverse-branch points in New York, DeKalb feeds two Manhattan trunks that are very close to each other, especially in Midtown, to the point that one-seat rides to every stop have limited value. It should make a decision about whether to run the B/D together on Fourth Avenue and the N/Q on Brighton (switching the Q and D) or the reverse (switching the B and N), based on origin-and-destination data. Some passengers might bemoan the loss of one-seat rides, but most would cheer seeing their trips sped up by 4-5 minutes.
Regarding which lines to pair, it may also be important to maintain cross-platform accessibility for those with mobility impairments. By sending the 6th avenue trains down Brighton, as you have it, access via cross-platform exchange is maintained for all stations, even if this means taking the R to reach the Broadway line stations.
Oh, right, because then the priority is not speed, and telling people from the Brighton Line to take the R is almost okay (almost).
I live off the R south of Atlantic and if I’m going to midtown (rarely, as I work FiDi and usually bike to work) I frequently have to make the decision of switching to the N or the D at Atlantic. I never think to switch to the Q as it’s a far walk. And I wouldn’t walk to the 2/3/4/5 since they go downtown and the N/D are right across the platform.
But Alon raises an important point — it always seems to take forever and hardly ever feels as if “you’re saving” time when you take the N/D shortcut from Atlantic. It always plods over the Manhattan Bridge. None of the time savings like when you take the C from 125th to 59th, even though, Atlantic to Canal should be fast!
Do you not switch to the Q (or B) at DeKalb?
Thank you for writing this post! I’ve wondered why these trains are so slow for a long time. I assumed it was because of the complicated switching but the info about the signalling adds another layer. The 4 tracks on the Manhattan Bridge really should be seen as the primary Brooklyn-Midtown express but they are not treated that way. They did 16 years of work to fix that bridge and then they run slow trains over it. I’ve wondered about the possibility of enlarging the station so all trains could stop and did a sketch of how it could be done, but it would be extremely difficult at best.
Can trains travel at regular speeds over the bridge even with better signals and less track switching? I know the design of the bridge, with the trains on the outside of the span, is problematic to begin with. Getting the DeKalb-Grand/Canal down to 5 minutes would be tough. I’ve never done it in less than 7 minutes and that’s when trains have 0 delays and run quickly. It can often take 10 minutes or more with all the stopping north of DeKalb. If you time it between DeKalb and Atlantic or Pacific, it often will take 3 minutes, and there’s not even a switch in that area. Those tunnels have lots of tight curves. I don’t think you could get it much under 2 minutes. I doubt Atlantic-Pacific to Grand/Canal could be done in less than 8 minutes, even in an ideal situation.
Even without delays, trains crawl through the interlocking. I wouldn’t be surprised if most of the slowness were due to overcautious timers and unfortunate track geometry.
As someone who has lived on the Brighton Line before, I would point out that the DeKalb recombination allows Brighton Line riders one-seat rides to destinations in 2 different directions beyond the Midtown core; namely, on the B train, the UWS and the Bronx over the Eighth Avenue Line, and on the Q train, the UES and Astoria. It also gives Brighton Line riders a greater choice of transfer points to other lines radiating from the Midtown core. The same is true for Fourth Avenue Line riders, with the D train a convenient trip to the Bronx and the N train a convenient trip to Astoria. I certainly believe that the rider value of the DeKalb recombination for passengers through-traveling the core to destinations on the other side of the core is greater than the inconvenience of spending a couple more minutes waiting on the train.
Indeed, it can be said that the entire point of “reverse” branching is to allow riders along a branch a one-seat ride to more than one other branch on the opposite side of the core. Operationally, this can be difficult (hence the failure of the H system that created the Times Square shuttle), but when those operational difficulties can be overcome (even with a couple more minutes delay), it doubles the destination options along a branch, which increases the value of the branch more significantly than a couple more minutes delay reduces that value. Indeed, the intrinsic value of branching in allowing more destinations is more significant than the delay caused by switching or the “reverse branching” status of where the branching occurs. (However, it does seem to be the case that the disvalue caused by operational difficulties due to branching is worse than the rider inconvenience of a well-designed transfer.)
Lastly, I would like to point out that this particular combination of the B and Q to Brighton and D and N trains to Fourth Avenue does create operational fiscal savings in allowing the B train to run as a limited-service express train without the need to run a “B shuttle” to any branch during the off-peak. Switching the B to run to Fourth Avenue and the D to run to the Brighton express tracks would create the need to either run additional, costly overnight express service, or run overnight shuttles on the Concourse Line in the Bronx and the West End Line in Brooklyn. Likewise, switching the N to the Brighton Line for the B to the West End Line means the end of the savings of having the B as a limited service train. On the other hand, switching the N to run on the Brighton and the Q to run on the Fourth Avenue and Sea Beach Lines is largely meaningless from an operational savings standpoint as both services are, and would remain full-time services.
However, switching the D to the Brighton Line and the Q to the Fourth Avenue/West End Line, from an operational savings standpoint, has the least impact from a operational savings standpoint, as the B train can remain the limited service train, and the D and the Q remain full-time services. This also meets your goal of undoing the DeKalb recombination, with the B and D trains on the Sixth Avenue and Brighton lines, and the N and Q trains on the Broadway and Fourth Avenue lines. Still, this would also reduce transfer access from the Brighton Line to the numbered trains at Union Square and Times Square, while unnecessarily increasing access for West End Line riders to the numbered lines since West End Line riders can already access the same stations with a transfer to the N train on the Fourth Avenue Line; this impacts Brighton Line riders the most, and Brighton Line riders tend to have more political clout than West End Line riders since the Brighton Line serves riders from large portions of Southeast Brooklyn beyond where the 2 and the 5 trains end at Flatbush Avenue. I am just not convinced that, for the Brighton Line, losing that much transfer access to the hubs at Union Square and Times Square is worth the extra couple minutes of time savings at DeKalb Avenue.
Brighton line riders have access to the IRT at Atlantic Terminal, and access to the 6 Train at Broadway-Lafayette. As a daily commuter from 7th Ave to Rock Center, I’ve seen the reliability between Dekalb and Grand completely fall apart, such that I schedule an hour for what should be a 40 commute. An actual saving of 5 mins, plus the added reliability, could realistically save me 20 mins.
No, the point of reverse branching is providing one branch with multiple routes *through the core*. As the 2/5 demonstrate, there need not be multiple branch/branch pairings.
While I haven’t examined origin/destination data, I cannot imagine that the aggregate time saved by current through
-riders exceeds the aggregate time wasted by core-bound riders, if only because there are significantly more of the latter. Reverse branching increases trip time on *every* branch involved and unavoidably reduces capacity.
I was about to write the same thing. There is an order of magnitude more people traveling to/from Midtown during the subway’s most crowded periods than to UES/UWS — let alone LIC/Astoria/da Bronx. “Reverse” branching hurts frequency, shrinks capacity, wastes track, hurts speed, hurts reliability (as one line delay propogates through all the other lines that at any point share tracks — e.g., a delay in the N in Brooklyn causes a delay in Washington Heights, in the Bronx, and on the QB Express Lines as the N interlines with the a line that at some point interlines with the mentioned lines), and hurts the ability to automate trains. While having one-seat rides to everything is nice (and politically popular), it comes at a significant cost to overall logistical efficiency, and faster, frequent, and more reliable service for everyone.
at the cost of making many people, very roughly half, who have a one seat ride, change trains.
No, not half. People going to Midtown are fairly indifferent about Sixth Avenue vs. Broadway: Herald Square is on both, 42nd Street is a long block apart, 49th Street is a long block apart plus a cross-platform transfer to the R/W, 57th Street is a long block or 4 short blocks apart.
People come in from the other side of Midtown too. Or Lexington Avenue etc. is a long way from 7th/Broadway.
Huh? I doubt someone on the 6th Ave Express Lines cares thaaaat much about having to walk an extra block to a job on 7th or 8th Ave. (certainly not enough to transfer for a large percentage) and a Broadway Express can commuter cares thaaat much about having to walk an extra block to 5th, Madison, or 6th enough to transfer at Barclays, Canal St., or Union Sq. East of Lexington Ave., both 6th & Broadway Lines would have to transfer to Lexington Ave Lines, anyway.
As for jobs in West Village, Union Sq, UES, UWS, Queens Plaza, the 4th Ave & Brighton Lines can learn how to transfer just like the rest of the world does to those secondary destinations.
Keep coming back to this. Reality is that there probably will be far more Brighton/4th Ave. Line workers in FiDi (who all already have to transfer to R or 2/3/4/5 at Barclays) plus Brighton/4th Ave. workers between 8th and Park who still won’t have to transfer than Broadway Express Line workers on Lexington Ave., and others who will lose their one-seat ride. All who currently have to transfer or still won’t have to transfer benefit from the increased speed, frequency, capacity, reliability, etc. I have mentioned. Those who have to transfer will have some of that hassle softened by the increases in speed, frequency, reliability, etc. The pruning of branches is of net positive transportation value to the entire system, even if it is of negative value to some commuters.
No one at the MTA, with access to computers for decades, has ever thought about it. Ever.
Nice Article in Vox.
Some of the delays associated with interlining may be not so much with the interlining per se, but with switching/dispatching policies that go along with the merges. In other words if it is a goal to avoid two or more of the same line coming into the station back to back while the second line gets no trains, that goal could be relaxed sometimes to keep things moving (people would complain of course, but . . . ).
I do not believe that the dispatchers in New York are strict about this, for two reasons:
1. I have seen two trains of the same line back to back at a few places.
2. Adam Rahbee complained to me that London used to insist on resolving merges on branches in the scheduled order, so delays on one branch would propagate to the other branches; once this policy was changed, London trains got more punctual. He notably did not complain about this re New York, even though in our conversation we extensively talked about New York’s punctuality problems.
The best way to route the trains would be to have b and d trains along 4th Ave and n and q along Brighton. The reason is that it would be easier to make transfers if needed between the lines by using the r train or the 6 train. 4th Ave riders can reach Broadway by transferring to the r at Pacific and then transferring again at DeKalb. Brighton riders can transfer to the uptown 6 at canal and then to 6th Ave trains at Bleeker.
If the trains were reversed 4th Ave riders would still reach 6th Ave by transferring to the r at Pacific and then transferring again at DeKalb. Brighton riders though would not have as smooth of a transition as they would have to take a downtown 6 and thus would be going out of their way.
Of course, the main point is that for the vast majority of riders, this is unimportant as they are heading to the same general area and are indifferent as to 6th or Broadway. Solving the reverse branching problem means more trains can travel on both corridors and easing congestion for everyone.
Riders heading to destinations in Midtown may be more-or-less indifferent to the 6th Ave Line versus the Broadway Line, but riders transferring to other lines will be annoyed at longer transfer wait times, reduction of transfer points, and the possibility of needing a transfer to an additional train. Transfer time in the NYCS is not a “negligible” amount of time, and less convenient transfers result in significantly longer trips.
Yes, it’s easier to transfer from the 6th Avenue Line to the 8th Avenue Line and from the Broadway Line to the West Side IRT and the 7. But the other transfers still exist, they just require walking a long block. And for the most part, people living in that part of Brooklyn are going to Midtown and not to Central Park West or to the parts of Queens only served by the 7 or the E/F but not both.
Do you have exit data or O-D data showing that most riders from southern Brooklyn, especially Brighton Line riders, are headed to parts of Midtown closest to 6th Ave or Broadway?
I have jobs and work data; most riders are headed to Midtown from Herald Square north, with some more going just south, like Madison Square. Even Union Square is not a major job destination.
Job and work data is not a sufficient substitute for exit data or O-D data, since there is not necessarily a one-to-one correlation between a job in Midtown and a resident in Brooklyn. Also, many rush-hour riders are not necessarily even heading to work, but to schools, hospitals, and other destinations. Many New York City high school students, especially, rely on the subways during the AM peak to get them to schools on the other side of the Midtown core, since New York City high school students attend schools around the city due to school choice and magnet programs. As well, significant numbers of local college students in New York City attend colleges on the other side of the core; it’s not uncommon for students attending City College in Harlem or Lehman College in the Bronx to be commuting from Brooklyn, or students attending Queens College in Jamaica to be commuting from the Bronx or even Staten Island. Commuting in New York City is a lot more complex than bringing workers into a point core, because the Midtown core is much too big to even be well-serviced by a handful of major stations at key point locations. because there are a lot of important destinations outside the core that draw a lot of peak travelers who are not necessarily commuting to work, and because most transit trips are not even commuting trips at all.
I don’t think it’s really true that most New York subway trips are not commutes. There are around 2.9 million subway roundtrips per weekday, and 2.2 million transit commuters in the city. There are about 1.2 million bus roundtrips per weekday, but bus-only commutes are likely rare (the average bus trip is 3.4 km); the overwhelming majority of New York bus trips are likely connections to the subway or errand trips. As a first-order estimate, it seems reasonable that two-thirds of subway trips in New York are for work.
This figure, two thirds of subway rides being work trips, is almost certainly higher at rush hour. The school peak is earlier than the work peak, especially for people going to school on the other side of Manhattan. For example, Bronx Science begins class at 8 in the morning; students coming in from Brooklyn would be passing through Midtown around 7:30, when trains run at full rush hour frequency but aren’t as overcrowded as they would be an hour later, and transfers at Herald Square (or Q -> 4 at Union Square for Bronx Science) are easy.
Why guesstimate when you can ask the O-D modelers what their data indicates? (Also, Bronx Sci is not the only high school in the city where students use transit to get to. In a city with 1.1 million public school students where many use public transit to get to school, that still comes out to a significant proportion of transit trips coming from public school students.)
Bronx Sci is just the one where I looked at bell times. I don’t think it’s much different at other schools.
Should the B or D be the Brighton Express?
My assumption is that express services should be consistent. So if there’s no change on Central Park West, the B should be local and the D express. If there is a change as I’m proposing in my deinterlining post then the trains are going to make the same stopping pattern from Atlantic north, so it doesn’t matter what you call the local and what you call the express.
While the proposed deinterlining speeds things up north of DeKalb it doesn’t appear to do anything to improve DeKalb to Atlantic/Barclays times and it’s that stretch that’s so costly for the 4th Ave services. The N is the super-express that skips DeKalb but nonetheless it takes two more minutes to get from Canal to Atlantic than the Q. What can be done to speed up that section?
I suspect it’s part of the same interlocking.
Listen up y’all…..It seems like the old BMT seemed to do a better job at handling train movements at this DeKalb Av-Gold Street interlocking complex under Flatbush Avenue near the Manhattan Bridge. Many years ago the BMT even had Nassau Street full time services coming in from the Williamsburg Bridge as well, and they did it successfully. It maybe time to dig out the old schedules, and learn how to run a railroad successfully. Back then you also had railroad people that knew their railroad running things instead of a bunch of Ivy League educated fools that only knows how to count beans instead.
I mean, the origin of high New York construction costs is in the 1920s and 30s… and before the Chrystie Street Connection opened, train service on the Manhattan Bridge was so asymmetric it led to bridge deformations that required long-term shutdowns. So please, let go of that MAGA fantasy of a better New York before mass education and start learning from countries where instead of an Ivy League you have Grandes écoles or Todai or ETH or Max Planck or SNS.
I personally think that another escape route that was planned back around 1953 that would have helped out a great deal, was to have another “Plan-B” was to connect the DeKalb Avenue-Gold Street Interlocking into the IND Rutgers Street tunnel, by a new short tunnel connection turning left under Tillary Street, with a new connection at Jay Street bring it into the York Street Station just before the Rutgers Street Tunnels begin. Or bring back some sort of Nassau Street Service just to ease out the routing a bit.
The way it’s set up today is fine from the bridge north (except for the intersection-without-a-transfer around Grand Street), the problem is the recombination to the south. Looping to Nassau isn’t going to help, and if anything would make things worse because nowadays, and honestly even in the 1950s, Lower Manhattan is a much less compelling job destination than Midtown.
The biggest problem for the BMT Southern Division today is that all trains coming off of the Manhattan Bridge. Before entering DeKalb Avenue station or using the bypass tracks into Pacific Street, that all trains coming off the north side of the Manhattan Bridge must STOP at the double RED signal next to a punch-box. At this location the train operator has to STOP their train, and to push a button so that their trains gets the appropriate line-up, and then proceed when you get the correct line-up when the signal changes from double RED, to GREEN over YELLOW to use the bypass, or a YELLOW over GREEN which sends you into the DeKalb Av station from the North Side of the Manhattan Bridge. Now coming off of the Manhattan Bridge from the south side or Broadway BMT, again must also come to a full stop before a set of double RED signal near an emergency exit, then punch their appropriate button which when they receive a double YELLOW signal, which sends the train into a left track that dips-under the the track coming off from the north side of the bridge that serves the DeKalb Avenue Station, then rises again to merge left with the bypass track coming off the north side of the Manhattan Bridge to bypass DeKalb Avenue. When you push a button and get a double GREEN, the you will get a straight line-up into the DeKalb Avenue Station stop. THIW’s my friend.
Pretty sure the punch boxes used to be at Grand St and Canal St and the descriptions follow the trains across the bridge, and for all I know that’s still how it works. The reason the trains stop at red signals is because there are two trains that simultaneously need to use the same track, like a B and Q arriving at the same time, or a D and N, which is hard to deal with because that would require tightly synchronizing the operations on the 6th Ave and Broadway express tracks. And of course a train like the B interacts with the C, which interacts with both the A and E (both quite frequent services), and the E interacts with the F and M, the M with the J/Z, and also the R, which also has to share the 60th St tunnel with the N and round and round it all goes.
Or run Second Avenue trains through the Montague Street Tunnel. Reusing the Nassau Street tracks that don’t get much use today. Or ever will if Williamsburg Bridge trains are going to go up Sixth. They had something in mind when they put the express tracks under Prospect Park. Shift the West End Trains, today’s D train, to Second Avenue via the Culver express tracks. Gets West End trains out of DeKalb… Either plan might mean tearing down a skyscraper in Downtown Brooklyn. The tenant might not be agreeable but could be convinced… The MTA building..