redundancy in transit networks: a good thing?

Transit planning consultant Bob Bourne is thinking about the Brisbane flood's impact, and wondering whether building more redundancy into transit networks is a good idea:

My heart goes out to everyone affected by the floods.  It can be devastating on so many levels, individual lives lost; extensive property damage to individual residences, and infrastructure damage.  I managed the system in Ames, IA during our floods in 1990, 1993, 1998, and 2005 and I have been assisting the Cedar Rapids, IA transit system in recovering from their 2008 floods.  I worked in Chicago during the blizzard winters of 1977-78 and 1978-79 where the city and suburbs experienced several weeks of paralysis due to the continuous heavy snows as well as way too many blizzards in Iowa over the years.
In the U.S. buses typically operate without a lot of redunancy in the route network.  Your commentary on numbering overlapping bus routes and make them understandable to the riding public is interesting and implies that there are lots of routes serving several corridors.  In the U.S. that may be true, but usually the headways are pretty well trimmed to provide the absolute minimal level of service.  When you add demand due to adjacent services becoming inoperative, the existing routes are overwhelmed.  Overloading causes extended travel times and buses cannot make their normal cycle times which exacerbates the problem.  Throw in a street network in chaos and the bus system will be criticized as not meeting the needs of the citizens in the time of crisis.  No easy way to explain the problem.
The other problem that we had in Ames, Chicago, and Cedar Rapids was that some of the drivers lived in areas that were flooded or had immediate family in those areas.  They needed to tend to their family/housing priorities and this decreased the number of people available when the workload  of more passengers and longer travel times increases.
At some time in the future, after everything settles, perhaps you could solicit comments on building redundancy into your transit system.  Sometimes, it is good to have lightly used routes that can be cancelled in a crisis allowing redeployment of drivers and vehicles.  Sometimes it is good to have headways with a loading standard of less than 125% of seats at the peak point on the route instead of cramming buses with 150% or 175% of seated load.   Your 10 or 12 minute frequent headway concept can provide additional resources if you need to cut it back to 15 to 20 minutes during a crisis.
After the September 11, 2001 disaster in New York, the subway system was able to recover quickly because the lower end of Manhattan was one of the few places in the subway system where there was some redundancy.   Multiple routes close to each other and at the end of some routes made it easy for commuters to resume their normal lives long before the reconstruction of the subway damage.
Redundancy is not favored by policy makers and can add to costs.  However, a system with excess capacity will perform well in times of crisis and will provide addtional service during normal times.
Our prayers are with everyone who is suffering through this disaster and we hope that good luck will shine on Australia again.

The kind of redundancy that Bob praises is something transit planners spend much of their time trying to get rid of, because on typical days when we don't need it as redundancy, we call it duplication and waste.

Transit agencies work on such tight budgets that it doesn't make sense to run, say, a bus line next to a rail line, doing the same thing, just for the redundancy.  If the rail line is serving the market, the bus should be off somewhere else, providing unique mobility rather than duplicating the rail.

This is especially true in small cities like Bob's hometown of Ames, Iowa, or Great Falls, Montana.  These networks' resources are stretched tightly to create the maximum amount of mobility for the budget.

Having said that, there are a few situations where an efficient network is also a redundant one.

Classic high-frequency grids provide redundancy for transit in the same way they do for cars.  If one segment in a grid goes down, there's a parallel line 800m away that you can walk to in a pinch.  It will probably allow you to complete the same L-shaped trip that you intended to make on the disabled line.  

Grid with trip

Ferries are more complicated.  The long cross-city run of the CityCats mostly connects stations that are also connected by bus.  The bus trip generally runs a shorter distance at a higher frequency, though it may require a connection.  So there's no question that the intrinisic attraction of the ferry is part of what keeps it busy.  There may also be secondary issues, like the legibility problems of much of the bus system in downtown Brisbane, where most connections occur.  But there are also situations where CityCat and the smaller CityFerry does a link that's simply impossible by road, or much, much longer, and in these cases the ferry wins on pure mobility grounds. 

Of course, bus operators generally have backup fleets in case they need to suddenly replace a non-redundant train or ferry line that goes down.  In Australia, there are often standing agreements between government and private operators to shift buses into this role, and given a day's warning — which Brisbane had — it's not hard to replace a failed network segment with buses even while running the rest of the bus network.

So is redundacy a good thing in disasters?  Of course it is.  Is it a reason to design networks that are redundant all the time, at the expense of more mobility that could be provided at the same cost?  No, probably not, because you're weighing a rare disaster against daily inefficiency.  Are there styles of network design that are both efficient and redundant?  Yes, the high-frequency grid comes to mind. 

In really big and dense cities, you can also get both redundancy and efficiency, because there will tend to be overlaps of service just to provide capacity into dense centers like Lower Manhattan, and in these cases, as Bob notes, redundancy is often possible.  The key there, however, is that the duplication of services isn't justified by the need for redundancy, but rather for the sheer capacity need, and providing necessary capacity, of course, is part of efficiency.


16 Responses to redundancy in transit networks: a good thing?

  1. rhywun January 14, 2011 at 4:41 pm #

    Another kind of redundancy might be express vs. local service, if you are lucky enough to choose either (as I am). Here in NYC, my express service costs double the local service, but gets me there in half the time and more comfortably. I only take the express rarely as a “treat” to myself – but I love having the choice.

  2. FFolz January 14, 2011 at 10:01 pm #

    Bare minimum –> reduced modeshare –> skeleton system –> utter failure in crisis.
    The bean-counter mentality reached its nadir in Washington, D.C. when the Metro proposed to slash packed bus lines in favor of “feeding” patrons into the subway (less convenient, btw, for the actual patrons, who needed crosstown service and local stops), a strategy they were only reluctantly convinced to give up when they maxed out their central subway capacity! Patron resistance was not a factor because it failed to reach a political crescendo–which is unsurprising given that those most affected were the working poor and low-level federal workers conditioned to bow their heads and bear it.
    Crisis response? Bah! Everyday modeshare is where it’s at, and beancounting is a wonderful way to take your modeshare right down to where the sun don’t shine.

  3. In Brisbane January 14, 2011 at 10:01 pm #

    Redundancy is great, you would not believe how many times the Tennyson line that connects the Beenleigh and Ipswich lines has been used- storms, train faults, power outages, incidents, trees and so on.
    The single most useful piece of railway track in Brisbane!

  4. ant6n January 14, 2011 at 10:15 pm #

    In Berlin, with the recurring S-Bahn meltdowns since 2008, it is good that the network provides some redundancy with the subway, tram and bus lines – although these modes of transports are getting somewhat strained these days as well.
    The irony is that the meltdowns themselves are caused by the privatization of the S-Bahn system, and the desire to put it on the stock market, meaning a lot of rationalization. This caused redundant rolling stock and redundant maintenance facilities to be scrapped, which in turn caused ridiculous shutdowns at times – only 1/3 of the rolling stock required for a normal schedule was available at certain times (e.g. first week of 2011).
    (The same problem is plaguing DB as a whole, with its market-orientation, reducing reserves(=redundancy) to increase profitability. It gets away with it because it basically is a monopoly.)

    Geographical redundancy is probably less important for buses than for rail lines, because the road network can provide some flexibility. But keeping access to some extra vehicles is probably a good idea.

    In Montreal, there are some bus lines that are redundant to the metro — these seem to mostly exist since the stations are not accessible, so the buses get a lot of old people etc.

  5. rhywun January 15, 2011 at 12:40 am #

    You’re probably right that much redundancy, of the sort that isn’t justified by demand, is only possible when it’s subsidized by the government. Normal businesses can’t afford it. I don’t know much about privatized transit (we have basically none here in the US), but your anecdotes about Berlin make it sound like the system is particularly badly run if they can’t even keep up with existing demand. Maybe they need some competition…? Which is the point where I stop understanding how private transit is supposed to work – how do you introduce competition on shared lines, for example.

  6. Jack Horner January 15, 2011 at 2:13 am #

    When the Hobart bridge fell down in 1975 they borrowed ferries from Sydney. I bet those little ‘I-think-I-can-I-think-I-can’ ferries which spent their days paddling across Sydney harbour had fun riding the waves to Tasmania.

  7. ant6n January 15, 2011 at 6:57 am #

    The way it works (in Germany) in general is that the state governments or the local (public) transit agency makes a call for bids for the operation of the rail lines (sometimes some lines, sometimes a whole system). The contract has a runtime of several years (generally 5-12 or so), and specifies how much service is supposed to be provided. Revenue may be shared, or not, but the service is generally subsidized (only long distance rail is not).
    This system generally works, because there is competition for regional lines (where many are operated by non-DB companies) and S-Bahn systems (where one small system is operated by a non-DB company). I think around a fifth of the rail lines are operated by non-DB companies. So most of the time the lines are still operated by DB Regio (which belongs to DB) anyway – who nevertheless seems to provide higher quality contracts if there is a bidding process before rewarding the contract.
    The system generally works because the standard for (electrified/non-electrified) regional rail and (electrified) S-Bahns is the same all over Germany – so there can be competition. So if one operator fails to fulfill the contract (for example by only having 1/3 of the contracted fleet operating like in Berlin), then the contract could be cancelled and rebid. Except in Berlin (and Hamburg), which built their S-Bahn systems 40 years before the rest of Germany – instead of 15v/16.7Hz overhead, they have a 750v third rail. And since no company can wish up 1200 cars S-Bahn quickly, and you cannot convert 330km of lines quickly into overhead (especially since some tunnels have a too small loading gauge), the city is stuck with this company. The possibility of contracting out at least some of the system out to another company was passed over because the politicians didn’t want to split up the network to multiple operators (which may be less efficient), although some say it was to save the jobs of current S-Bahn workers.
    So the take away message with privatization is that if you want to privatize operations (the infrastructure and transit agencies remain public), then you have to provide for competition as well. Creating a private monopoly is just a bad idea, and results in companies which cut all their reserves.
    (sorry for high-jacking the thread, but it’s somewhat related, I guess)

  8. Paul K McGregor January 15, 2011 at 11:39 am #

    When I started working as a service planner in Dallas, there was a proposal to operate a bus route parallel to the light rail line and we were told by the consultants that it would not be needed. The redundancy of the network would be the parallel street network that you could operate a bus bridge on if there was some failure in the operation of the light rail line. Otherwise, if there was not sufficient demand for both, you would not operate a parallel line. Eliminating redundancy is just not about saving money but as a way to reallocate resources to areas that can be used more productively either through funding light rail, expanding service into new areas or beefing up service in existing areas.
    An interesting note related to ferry service that ties to this is looking at the history of how the Water Transit Authority in the San Francisco Bay Area has evolved. When the agency started out it had three missions: 1. to consolidate all of the ferry service except the service operated by Golden Gate Transit under one umbrella; 2. to identify new locations for ferry terminals and expanding ferry service, and 3. develop enviromentally friendly ferries. A few years ago, the name of the agency changed to Water EMERGENCY TRANSPORTATIOn Authority and as you can see from the name change, it added a whole new responsibility to their mission. The intent now is to use waterborne transport as the primary means of transporting first responders and emergency care people in the event bridges and even BART were to fail. Unlike floods, earthquakes give no warning so your planning beccomes a bit more complex trying to anticipate every possible scenario. Emergency preparedness and operations does play a big role for transit agencies especially in areas that are prone to natural disasters like California.

  9. Ted King January 15, 2011 at 1:14 pm #

    Redundancy takes several forms : parallel lines, spare equipment, and alternate routes for fixed guideway lines. San Francisco’s skeletal LRV route system makes the cost effectiveness of alternate routes obvious. The addition of the San Jose Ave. extension to the J-Church line filled in a gap in the system.
    Its big benefit was to simplify service on the J-Church and N-Judah lines by freeing them from having to run downtown before entering revenue service*. It also added capacity for runs to / from Balboa Park BART stn. (part of what doomed the 26-Valencia), provided a high capacity parallel to BART between that station and Glen Park BART stn., and allowed for diversions in certain kinds of emergencies (disabled vehicles / tunnel problems).
    Yes, spare segments of track are un-cheap. But, as various systems have found out (SF, New York, etc.), the payback is substantial.
    SFMuni maps :
    *Historic note – In the PCC era the points at 17th + Church allowed a “J” to turn outbound for the run to 30th after transiting the Twin Peaks Tunnel and surfacing near Castro + Market. Similarly, the N-Judah would turn outbound via the points at Duboce + Church.
    P.S. I have a suspicion that leaving out a bypass track (just single – emergencies and non-revenue use only) for the Fourth + King turn-back has constricted the LRV traffic. Such a bypass would allow T-Thirds to enter the turn-back and avoid the draw-bridge and the heavy freeway ramp traffic on Fourth St. The Fourth + King intersection is a planner’s nightmare due to heavy traffic from cars, LRVs, and pedestrians. Luckily, SFMuni’s terminal stops for the #30, #45, and #47 are a block away on Townsend St. That still leaves some peak period Caltrain shuttles (#80X, #81X, #82X) to thicken the stew.

  10. Pat L January 15, 2011 at 5:56 pm #

    My experience in New York is that, especially since it is a 24-hour system, they take advantage of the redundancy for maintenance purposes. From a rider’s perspective, it sometimes seems like the MTA is trying to make sure that no two weekends feature the same transit network, but the system is such that many sections of track can be shut down for maintenance without affecting large-scale connectivity.
    This is probably only a factor for larger systems, but it’s something redundancy is useful for outside of disasters. Disasters and ordinary breakdowns sort of run together at some scale.

  11. EngineerScotty January 15, 2011 at 6:09 pm #

    A simple thing for light rail that unfortunately, the budget-constrained Milwaukie MAX line is skimping on:
    Crossover connections between the two tracks of a dual tracked line.
    The more of these there are, the easier it is to minimize service disruptions when an incident takes a rail line out of service. TriMet is very good at quickly deploying shuttle busses to get around such an incident (obviously with a loss in performance while the shuttles are in use)–but the shuttles generally have to be deployed at (or near) a switchover point, so the trains can switch to the opposite track and proceed back in the opposite direction. IIRC, the MLR FEIS only specifies one or two switchover points (not counting the terminal station) along a 7-mile route.

  12. rhywun January 15, 2011 at 10:16 pm #

    Thanks for the description of privatized transit in Germany. I’ve heard some horror stories about the privatization of British Rail, but little about similar efforts in Germany. I lived in Würzburg 25 years ago – much of how I think the way transit should work, I learned there; I suppose I should return some day and see for myself if things have changed for the better or worse.

  13. Alon Levy January 16, 2011 at 2:29 pm #

    Does anyone reading this know how this works in Tokyo and Calgary? Tokyo has a reputation for things working day in, day out, and Calgary specifically mentions reorganizing the buses for strict feeder role as one of the factors contributing to the C-Train’s success. Do these networks actually succeed with less redundancy, or is there a lot of redundancy that isn’t visible from my 30,000-foot vantage point?

  14. Jarrett at January 16, 2011 at 2:47 pm #

    I don't see much redundancy in Calgary.  A city the scale of Tokyo will have some redundant capacity just because they can fill all the capacity they provide.  Certainly, Singapore has plenty of buses flowing right next to its subway lines, all of them full on the peak. 

  15. GMichaud January 17, 2011 at 6:36 pm #

    Redundancy should be a feature of all transit systems, especially in mid to large cities. It is what makes a system function well. Alternate routes should probably the main focus of redundancy. Without redundancy the transit system is one dimensional and shallow.
    Even with electric cars, the demise of the auto is at hand, I dread when oil becomes truly scarce. Great wars will probably be the result. This is in a large part due to the lack of commitment to transit and redundancy.
    An integrated transit system should include walking, bicycles, taxis and other forms of transit which means city planning, density, and public space among other questions are important components of redundancy, not just routes.
    Systems I am familiar with that begin to attain these qualities include New York, Toronto, London, Helsinki and Hong Kong, Hong Kong is primarily privately managed.
    The lack of well thought out redundancy actually will cost money because riding transit becomes less desirable, bringing in less revenue and creating an environment of failure.
    In St. Louis where I live and in many American cities the bottom line is that autos still rule. The prejudicial anarchy that passes for governance probably won’t change until absolutely forced to. Certainly reasoned arguments don’t seem to be an answer. In fact discussions such as this never make the mainstream. It is a serious flaw in democracy.
    From my viewpoint, redundancy is a necessity in successful transit systems, even without any concerns for disasters. Disaster planning and security make redundancy essential.

  16. Owens31Patty August 11, 2011 at 4:53 am #

    Don’t have enough money to buy a building? Worry not, just because that is possible to receive the mortgage loans to resolve such kind of problems. Thence take a short term loan to buy all you want.