The whys and wherefores of MAX bus bridges

In the previous post, we lamented the recent spate of (sometimes bizarre) incidents affecting MAX service, in particular a car which ran off a freeway offramp and landed in the middle of Sunset Transit Center, shutting down MAX service on the westside for the better part of a day. (Nobody was badly hurt; the driver was arrested for DUI).

The topic swiftly turned to the contingency plans TriMet deploys whenever there is a major outage on the rail system–the bus bridge. A bus bridge consists of a fleet of busses transporting passengers between two out-of-service segments on the line. Nobody likes it–it is inconvenient for rail passengers, who have their trip times lengthened considerably (but certainly preferable to being stuck). It is inconvenient for bus passengers, who often see runs cancelled due to the need to service the bus bridge, and it is expensive for TriMet, who may have to pay operators overtime due to the unplanned additional service need, as well as pay for lots of unplanned deadheading.

And some bus riders claim that the practice is unfair to them–that bridging MAX, Streetcar, or WES is a rail problem, and thus ought not have any adverse affects on bus riders.

The mechanics of a bus bridge

A bus bridge occurs when a section of track goes out of service for an extended period of time. This may be due to a broken-down train, a collision, a problem with the tracks, signalling, or power lines, or any number of other reasons. Short outages generally don’t produce bus bridges–and in some cases there can be an aggravatingly long wait before a bridge is ordered (if it is a mechanical problem for instance, TriMet may try to fix it on site before taking the line out of service–which requires a mechanic travel to the problem, troubleshoot it, and decide if it can be fixed easily or not; meanwhile, trains back up upstream of the incident).

If a bridge is ordered, the section of track taken out of service extends to the nearest turnaround points on either side. There’s a limited number of places on the MAX line where trains can reverse direction–generally, at transit centers with pocket tracks (such as Beaverton, Rose Quarter, or Gateway); as well as the Blue Line turnaround near Galleria downtown, and at the ends of lines. Most of the MAX system (outside these places) is signalled in only one direction; and MAX trains are forbidden to travel backwards (against the signals) under normal operations (and certainly not with passengers on board). Thus even if only one half of the line is affected (such as by a broken-down train), the bus bridge is bidirectional; trains cannot pass the broken-down train on the opposite track, and a balance of trains on both sides needs to be maintained.

Thus, when a bridge occurs, trains will enter the pocket track or turnaround at one of the stations at the end of the outage, unload passengers, pick up passengers heading the other way, and then leave in the opposite direction. Busses then transport passengers to the station at the other end of the out-of-service section, serving intermediate stations. Depending on the situation, busses may also pick up passengers from trains stuck in the closed section (though passengers on a train involved in an incident may have to wait, particularly if the train is stopped in a place where safe unloading is not possible).

To do a bus bridge, you need two things: 1) busses, and 2) bus drivers. #2 is often the harder resource to come by–TriMet keeps a number of busses in reserve, even at peak times, and at off-peak times (when MAX loads and frequency are lower, and fewer busses are needed) there are even more unused vehicles available. TriMet doesn’t, however, like to pay drivers to sit around waiting for the phone to ring, so when a bus bridge occurs, drivers can come from one of several places:

  1. Supervisors and mechanics still current on bus training and licensure, and thus legally able to operate a bus
  2. Busses (and drivers) deadheading at the end of a run
  3. Off-duty drivers who agree to be called in
  4. Drivers diverted from operational bus service

MAX operators are generally not available for a bus bridge–many may not have current training or licensing, and trains cannot be abandoned along the line.

In many cases, there are not enough of numbers 1-3 to go around, so bus bridges are staffed, at least partially, with #4. Generally, busses and drivers are only taken out of regular service at the end of runs, as terminating a run mid-route and booting off the passengers would be rather rude–but if it is a bus you are expecting that is taken out of service, and the line is not a frequent one (or is frequently crowded), you won’t be a happy camper.

Needless to say, bus bridges can be highly disruptive to scheduled bus service.

The equity issues

Some TriMet riders, particularly those who mainly use the bus system, consider this situation inequitable–questioning whether or not it is fair to disadvantage bus riders for the benefit of rail riders. I generally take a holistic view of transit–both bus and rail are part of the same system (as opposed to competing modes); many users of TriMet use both modes, and to some extent view the distinction as a bit artificial. But given recent history (with a rail expansion coupled with the current financial troubles resulting in significant reductions in bus service), a decrepit bus fleet (with many vehicles lacking modern amenities like A/C or low-floor boarding), and a political culture which has appeared to view bus service as second-class (along with politicians and business interests who may advocate rail projects for reasons other than mobility benefits), it is understandable that bus riders object vehemently to the practice.

There have been suggestions that TriMet discontinue the use of bus bridges altogether–or at a minimum, restrict bus bridges to use of “spare” assets, and refrain from taking busses and drivers out of scheduled revenue service. When a bus breaks down, after all, it is generally not replaced for a while–passengers on board are simply asked to wait for the follower. (If it is an infrequent line, or if the follower is SRO, this obviously becomes inconvenient). Local bus service, while being subject to ordinary traffic jams, generally doesn’t suffer catastrophic disruptions. An incident involving one bus does not shut down the line, and busses can re-route around road closures in most cases. One could argue that if riders are to enjoy the advantages of exclusive-ROW rail (no traffic conflicts and a smoother ride), they should also endure the disadvantage (the possibility of catastrophic failure of the service).

On the other hand, if you view things from the point of view of causing the least inconvenience to the fewest number of passengers; a bus bridge makes sense. A bus involved in a bridge will generally be more full than one circulating through the suburbs–in many cases, more passengers will benefit from the bridge than will be inconvenienced by it. On the third hand, the benefit is asymmetrical, as the same groups of passengers “win” and “lose”, time and time again.

One other issue is finance. Erik H, in a comment on the prior thread, proposes:

There’s a pretty simple solution:

Require MAX Operations (yes, Operations – not Capital) to buy 100 new buses.

Those 100 buses are then put into bus service – and DEDICATED to bus service. Meanwhile, MAX then takes possession of the 1400 and 1600 series fleet. They are stored at Ruby or Elmonica. They become MAX specific assets.

When MAX craps out, the MAX Operators get to drive those 22 year old POS buses – with zero impact to bus riders.

As noted above, the critical resource is drivers and not vehicles. TriMet does keep a number of vehicles in reserve, and reserve vehicles are more likely to be older ones (newer busses are run all day, older ones mainly during the peak and/or emergencies; this is a big reason why express lines, including the 94 which Erik commutes on, often use the dregs of the fleet). As Bob points out, vehicles are capital goods and should be bought with capital dollars–using operating funds to buy rolling stock is simply not wise. And TriMet doesn’t, to my knowledge, a priori dedicate X% of funding to bus and Y% to rail; its funding allocation strategies are more flexible. That said, Erik makes a good point: Any time a bus is used or diverted for bridging a rail outage, its corresponding expenses (fuel, driver labor, and pro-rated maintenance) ought to be “charged” to the rail accounts and not to bus service, in order to be an adequate representation of the cost of offering the different types of service. This may be TriMet’s practice today; it may not be. Given that a claimed benefit of rail is that it is cheaper to operate on a per passenger-mile basis, this ought to be true even if contingency measures are taken into consideration.

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