Introducing the Golden Gate Mariner

by Rafael

This post is about an ambitious idea I had for a new regional light rail/streetcar line between downtown San Francisco and San Rafael in Marin County. While the primary purpose would be local and regional transit for residents of Marin county, it would also connect both them and Sonoma county residents (via connection to SMART) to high speed rail at the future Transbay Terminal Center.

A Brief History of Transit between SF and Marin County

Early in the 20th century, the only way to cross the Golden Gate Strait was with a ferry from piers along the SF Embarcadero to either Sausalito or Tiburon. From there, a standard and a separate narrow gauge railroad provided connecting passenger service to points north.

When the Golden Gate suspension bridge was designed to accelerate transit, the plan was to support streetcar service on two of its lanes. However, the actual construction never featured any rails because there was never anything to connect them to at either end. By the late thirties, transit agencies were switching to diesel buses which were more flexible and cheaper to operate. That is still the case today, but bus ridership suffered greatly once just about everyone could afford cars of his or her own. For a variety of reasons, electric trains - especially grade-separated subways - tend to be more popular with commuters.

The principal problems the popularity of private cars created for urban planners are road congestion and land use for parking spaces. Congestion also impedes bus and streetcar operations. Air quality issues related to gasoline cars have receded thanks to three-way catalysts. Comparable technology for diesel engines is much more expensive and was not even available in California before late 2008.

In a rare example of prescient regional transportation planning, an Army-Navy board convened after WW2 recommended the construction of a fully grade separated electric rail network spanning San Francisco, San Mateo, Marin, Alameda and Costra Contra counties. Since only the lower deck of the western span of the Bay Bridge had been constructed to support trolley service from the East Bay to the SF Transbay Terminal, the whole bridge was to be given over to motor vehicles. The new trains would run out to Daly City in a subway under Market Street, with a fancy new transbay tube across the Bay. Soon after, this plan became the basis for the civilian BART organization.

San Mateo soon bowed out, citing the high cost of full grade separation required to enable third rail operations. In addition, Standard Pacific already provided diesel-based passenger rail service into San Francisco. Keep in mind that at time, this was profitable, the peninsula was sparsely populated and no-one had even conceived of Silicon Valley.

BART engineers had picked 1676mm broad gauge for the new network, in part to provide mor stability for the planned Marin line across the Golden Gate bridge. Marin county withdrew from BART regardless. The primary reason was its limited tax base, but there was also some renewed discussion of whether the Golden Gate bridge could support the BART trains, which are longer than streetcars (though lighter per unit length, which matters more for bridge safety). Up to a point, the engineering discussion may have been a bureaucratic smoke screen: the Golden Gate Transit Authority was jealously guarding its turf, which included the bridge and toll collection on it.

Right of Way Preservation Efforts

Marin county did spend quite a bit of time and money on studies related to the old railroad lines, whose fortunes had declined due to competition from US 101, increasing opposition to logging in old-growth temperate rainforests, tunnel fires and the high cost of maintaining the Eel River valley line up to Eureka. Certain sections are prone to flooding and/or geologically unstable.

The county and its neighbor to the north, Sonoma, ended up purchasing the right of way between Corte Madera and Ignacio, just south of Novato Junction. Between Corte Madera and Sausalito, the old right of way is being preserved as a bike route called the North-South Greenway. Bicycles are serious business in Marin: millions are currently being spent on restoring the old railroad tunnels, something cyclists in Santa Cruz county can only dream of. Parts of the old line between Corte Madera and Tiburon are also being preserved as bike trails today.

The section between Schellville Junction (south of Sonoma town), Novato Junction and Eureka was taken over by the North Coast Rail Authority (NCRA), a California state agency created specifically to keep the ROW from being abandoned. In 2006, it leased the right to operate to the resurrected Northwestern Pacific Railway (NWP). It intends to minimally rehabilitate the line - top speed 10mph in some sections - to support the extraction of aggregate from the Eel River valley. Tracks still exist between Schellville Junction and Fairfield Junction with the Capitol Corridor main line, though they will also need to be rehabilitated before they can be brought back into service.

Coming full circle

In retrospect, many North Bay residents now regret Marin's 1961 decision to withdraw from BART. The Golden Gate bridge is now badly congested during rush hour, tolls have since risen to $6 southbound and all-day parking in SF has also become very expensive.

In 2008, a 2/3 majority of combined Marin and Sonoma county voters approved a sales tax hike to fund the resumption of passenger rail service between Cloverdale and the Larkspur ferry terminal under the name SMART (Sonoma-Marin Train). To preserve the option of double-tracking at some point in the future, a bike trail will run next to the restored line. Detractors rightly point out that that any future service to Sacramento and Oakland is just a pious hope at this point. For the moment at least, Marin county in particular is heavily dependent on its tenuous connections to San Francisco and Berkeley.

There is also concern that NWP's plan to support controversial mining operations in Mendocino county will lead to numerous heavy freight trains running through multiple Sonoma county towns at night, just to avoid conflicts with SMART's timetable during the day. NWP has already begun with rehabilitation work, so SMART may be forced to select FRA-compliant equipment such as DMUs from Colorado Railcar, which had briefly gone out of business in 2008.

Choosing FRA-compliant equipment would essentially kill whatever hint of a sliver of a chance there remains of ever laying heavy rail tracks south to Marin City, never mind Sausalito. Tracks across the Golden Gate and into downtown San Francisco seem even more outlandish.

Streetcar vs. Car, Sweet Car

Still, it's worth re-iterating that the Golden Gate bridge is badly congested, a situation that is unlikely to improve by itself anytime soon, if ever. FasTrak toll collection has certainly helped speed things along, but there are still plenty of people who prefer to pay cash. Restricting two lanes on 101 between San Rafael and the Marina district in SF to HOV vehicles would obviously increase throughput capacity, but it would also make commuting even more hellish for anyone who cannot - or will not - carpool. Private livery service is expensive and public buses not terribly popular.

One possible approach would be to forget about the Larkspur Ferry and terminate SMART in San Rafael instead. There, passengers would make a cross-platform transfer to a new light rail service which I've dubbed the "Golden Gate Mariner".


View Golden Gate Mariner (light rail) in a larger map

Provided cyclists agree to share the ROW as they already have for SMART, light rail should be compatible with current land use patterns in southern Marin county. The one significant caveat is that the old level railroad bridge across the Larkspur slough should be replaced. For a transit service that will run multiple times per hour, any swing or bascule section represents a risk to the timetable. The replacement should provide as much clearance as the adjacent freeway bridge. Fortunately, suitable light rail vehicles can handle grades as steep as 6%.

Service through Sausalito would be in streetcar mode. South of that point, there are two options:

OPTION #1 is to climb up to the Golden Gate bridge, run across that into the Presidio and head for the Marina District via Chrissy Field. Beyond that, trains could continue past Fort Mason to join up with the F-Market streetcar tracks along the Embarcadero, possibly hooking a left at 1st & Market to reach the new Transbay Terminal Center and looping back via Fremont Street.

The big plus of this option is that it avoids seriously breaking the bank by leveraging the existing Golden Gate bridge. It would not be necessary to dedicate lanes to streetcar service, only to ensure sufficient space in front of and behind the heavy light rail vehicle to avoid collisions and exceeding local load limits. In practical terms, that would not be easy to do. Railroads use block signaling, perhaps something comparable (but with very short blocks) could be used in this context. The streetcar lane could be monitored with video cameras, anyone running a red light would be fined.

This highlights the primary downside: sharing the existing bridge without dedicating one or two lanes to trains means inconveniencing motorists, even a potential safety hazard. Theoretically, light rail service would take more than enough cars off the bridge to compensate for the inconvenience. In practice, however, vehicle traffic volume tends to rebound before long as the population grows.

The other downside is that light rail is limited to low speeds in streetcar mode. The total distance for option #1 is only 20.8 miles, but it could take an hour to cover that distance.

OPTION #2 avoids the Golden Gate bridge, relying instead on a brand-new, dead straight tunnel under the Golden Gate between downtown Sausalito and Columbus Ave in SF. At 5.5mi, this isn't the shortest option for a bay crossing, but it does run along a ridge on the sea floor, this limiting how deep the tunnel would need to run.

The line would continue up Columbus Street in SF and joining up with the northern end of the Central Subway. Sharing track with that would require schedule integration, as SF Muni currently plans to run the Central Subway at 5 minute intervals during rush hour. If sharing is possible, the GG Mariner would connect to BART / SF Muni at Powell Street and to Caltrain at 4th & King/Townsend.

It would be possible to terminate the line at 3rd & Channel in Mission Bay. However, it would be useful to offer direct service to the TTC. Given that the complex vertical alignment of the Central Subway (option 3B per FTA's ROD), the only way to achieve that is with some new streetcar tracks to double back. The earliest opportunity would be Bryant Street just south of the portal, but it's a one-way street. It might make more sense to use SF Muni's existing tracks along King and Embarcadero, run past the ballpark and up 2nd (above the DTX tunnel). The line would end in a single-track loop via Natoma, 1st and Howard.

Still, single biggest advantage of option #2 would be the shorter distance and much straighter alignment into downtown SF and out to 4th & King. Line haul time from San Rafael could probably be reduced from an hour to less than 40 minutes. That would be a game changer in terms of modal market share among commuters. Compared to that, the awkward detour to get to the TTC is a small price to pay. In addition, option #2 would create a second fixed link across the GG strait, a very useful thing to have in case the Bridge or US-101 ever became unavailable for an extended period of time, e.g. after an earthquake.

The biggest downside, obviously, would be the fairly stupendous cost of constructing a bored tunnel under the Bay. The distance is much shorter than the one between England and France, but the ridership potential is also much smaller. There just aren't that many people in Marin county (or even Marin + Sonoma counties). A submerged floating tunnel, anyhow just a theoretical concept, is probably out of the question due to the high tidal currents in the Golden Gate.

Perhaps a conventional immersed tube might be viable, as long as it is buried deep enough to avoid undesirable interactions with the currents.

Rolling Stock and Yard

Since both options require a certain amount of streetcar service and would share some track and stations with SF Muni lines, the trains cannot be too long.

Regional light rail lines of similar length with sections of mixed traffic with local streetcars operate successfully in Europe, e.g. the WLB between Baden and Vienna, Austria. Their dual track line is 30.4km (19mi) long with a total of 34 stops, roughly comparable to option #1 above. WLB has run on overhead catenaries for over a century and serves 30,000 passengers a day at intervals of 7.5-30 minutes (varies by day, time of day and location). That corresponds to a modal share of ~40% of commuters, even though there is no single traffic choke point comparable to the Golden Gate bridge. Ticketing is integrated with the zone system used by the regional transit authority VOR.

WLB's new type 400 rolling stock is a custom low floor variant of Bombardier's Flexity Swift light rail product line. Each car is 27m long, doubly articulated, weighs 49 metric tonnes fully loaded and offers around 70 seats plus room for well over 100 standees. Typical trains feature 2 cars back-to-back, with the driver cabs at the free ends. For reference, WLB also operates some light freight trains on its own heavy rail tracks south of Schedifkaplatz and those of other railways.

Note that overhead catenaries and conductor rails (for low tunnels) are expensive but don't require full grade separation. For option #2, OCS is the only way to go. Option #1 could be theoretically implemented with a clean diesel powertrain as well, since the only tunnel is the short one in Mill Valley. Also, any proposal to add sturdy OCS poles and wire to the iconic GG bridge might well run into environmental objections.

Since most of the morning ridership on the GG Mariner would be southbound, it might be acceptable to make do with a single yard for overnight parking. The easiest location for that would be at the end of a short spur in Corte Madera, see map above. The location used to be part of the NWP line to Tiburon. The last trains of the day would dead-head there from San Rafael.