Parallel Subway Lines - How far would Goldilocks go?

Parallel metro rail lines

The Bay Area is a big metropolis. Not the biggest, but quite large. We have a metro rail (or subway) system called BART. We also have a regional rail system with Caltrain, while BART beyond Oakland and Berkeley acts more like a regional rail system.

What we don't have is multiple and separate rail lines that cross each other or run parallel like may cities do. In Washington DC, the Metro lines cross themselves three locations (Metro Center, Gallery Place/Chinatown, and L'Enfant Plaza). The Atlanta MARTA system makes a cross, where all lines meet at Five Points. In Los Angeles the lines meet at 7th St/Metro Center and soon Union Station.
In Boston, the colored rail lines meet at a plentiful 4 locations. However connecting the four stations are all in very close proximity, effectively making one large hub, not multiple ones like in other examples.

Why have parallel lines or a hub transfer station where lines cross? Having two completely separate lines, whether parallel or crossing overs people different ways, options, to get to city centers. With a cross of lines, it means trains can come from all directions. If parallel, it means that depending where I am, or where I'm going, I have two options. This is especially useful if one of the lines is crowded or if there's a train breakdown. I can always use the other line.

When looking at comparable city centers to Oakland or San Francisco, we see cities with similar densities like Washington, DC, Montreal, Toronto, and Philadelphia. All of these cities have parallel subway rail lines for at least two stations on each line. On average they are about 1/3 to just under 1/2 a mile apart; 0.35-0.45 miles apart to be precise, based on the cities I looked at.

Let's just look at parallel lines and stations for now. I ask, how far apart should a parallel line be in the Bay Area. Today we look at how far apart train lines should or could be in Oakland.

0.40 miles apart
Toronto's looping Yonge-University (#1) Line swoops makes a distinct loop through the heart of the city center, turning back at Union Station. Although only one line, it acts like two.

Washington, DC
0.34 miles apart
Washington's Metro system run by WMATA was built and designed in a similar time as BART. Much like BART, multiple rail lines. On the map shown, the parallel lines running north are 0.34 miles apart. The one to the left carries the Silver, Blue and Orange lines, while the line to the east carries the Yellow and Green lines.

0.43 miles apart
Montreal's has two metro lines, the Orange and Green run parallel for quite a long distance. Their separation varies, but is about 0.43 miles in the city center.

0.3 miles apart


0.43 miles apart between Broadway and Brush - the ConnectOakland I-980 proposal.

From this list of systems, parallel lines range from 0.3 to 0.43 miles apart, with the average distance between parallel rail lines in or at city centers is 0.3675 miles.

0.3 miles from Broadway is just west of Martin Luther King Way to the west and just east of Alice Street to the east.
0.43 miles from Broadway is to Brush St in the west and to Madison Street in the east.

So the I-980 proposal is in the range of existing parallel subway lines, on the outside edge of the range. Placing the parallel line on Castro St or Jackson St is 0.365 miles from Broadway - essentially the average distance in this small sample.

Finally, let's look into the past to a late 19th century Chicago where the Chicago Loop was constructed in a less than currently dense city. The north/south roads of the loop, Wabash and Wells streets are 0.394 miles apart, which happens to be about the distance between Broadway and 12th St and the center of I-980 at 12th St.

Note that none of these parallel rail lines are closer than 0.3 miles. Making stations too close means they are overly redundant and are not spreading out the area that would benefit from transit and from dense development. Making the rail lines in Oakland less than 0.3 miles, say running down Webster and Harrison would be a mistake based on this analysis. 


  1. New York has north-south lines under Park, 6th, 7th, and 8th. The last three are 280 meters apart between blocks, the first two are 620. On the Upper West Side the lines are under CPW/8th and Broadway (which runs as 10.5th), 700 meters apart; on the Upper East Side, under 2nd and Lex (3.5th), 370 meters apart.

    Of note, New York's east-west lines don't have a stop at each of these avenues. The L combines 6th and 7th, and the 7 combines 7th and 8th, with long walks between platforms. The east-west parts of the E don't transfer with the lines under 6th and 7th at all.

    This is related to why almost every major subway system has places where lines cross without a transfer: the target spacing between parallel lines in the CBD is a lot smaller than the target spacing between stations.

    In Paris, Metro 1 and 3 are about 900 meters apart, and in the center, where Lines 8 and 9 run parallel to 1 and 3, they're 300-350 meters north of Line 3. Every pair of intersecting lines has a transfer, except 9/12 (built by separate companies), 5/14, and 8/14 (Line 14 has large station spacing). But this is in the context of very tight stop spacing, except on Line 14.

    1. Great observations Alon! I had looked at NYC a bit, but less so Paris (in spite of having lived there for several years.) With NYC's lines closer lines than most (280 meters), I figured this was more compatible with the highly dense Manhattan. Although Paris is less dense than parts of Manhattan, it's still quite a highly dense city.

      I wonder what the Paris Metro planners were debating when they chose the alignments of the 1 and 3 lines in the 1800s. Was it more about - how do we get needed lines through busy parts of the city AND stay under streets, or was there consideration that these two lines would only be 300m apart. Likewise, when the 8/9 were opened in 1931 to 1933 along les Boulevards, did planners and engineers think of the short distance to the 3 line? Was it seen as a benefit, or a necessity due to the width of the boulevards to place it there or due to the density of jobs and housing.

      Good points on crossing lines. Shouldn't have stations too close together in spite of crossing a line.

      Regarding target spacing, I've heard BART folks say that if Oakland's Broadway tunnel were designed now, they would have only built one station (probably at 14th St) because the 19th and 12th st stations are really too close from an operational perspective.

      Line 14 is its own animal. Built so much later, and threading the needle between lines deep underground.

    2. Well, Lines 1 and 3 aren't thaaaaaat close. They're 3 stations apart on Line 4. Line 3 was at the time intended to be the relief to Line 1 (and Line 5 to Line 4, but it dips west in the north to hit Gare du Nord and Gare de l'Est); the center was intended to be Chatelet. I don't know what made the center of the city migrate northwest, to the Opera area, but evidently, by the 1930s, it was not a priority to build a line closely parallel to Line 1.

      Besides, the M8/9 alignment was really the only available east-west alignment, except the various streets forming the boundary between the 1st and 2nd Arrondissements. So either way, the line spacing was going to be tight. The city needed that extra capacity (I've read somewhere, I don't remember where, that like New York, Paris had its peak Metro ridership right after WW2 - and that was without the cross-river parts of M13 or any of today's M14).

      Interesting that BART people say that about Oakland, and not, say, that the Transbay Tube would be entering Downtown Oakland from the west and not from the south, to allow for SF-Downtown Oakland-East Oakland service. BART's biggest gap is that East Oakland-Downtown Oakland service has to continue north to Berkeley and Richmond, neither of which has much interest in going to East Oakland; this was something already criticized in the press at the time, IIRC in the Nation.

  2. actually Chicago has stuff even closer. The Red and Blue Lines and the Looped L together would make it even closer. since they're only a block apart. Blue to Red is 0.1 miles. Red to Wabash is 0.1 miles. Hence, Blue to Wabash is 0.2 miles. This is going east. Going west, Red to Wells is 0.3. Blue to Wells is 0.2


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