Monday, April 23, 2012

The Lurch

Last week I asked bus advocates to answer these questions: "Is there a bus you love? What is it, and why? How often do you take it? Would you complain if someone replaced it with a train that was at least as fast?"

One of the reasons I asked is that bus advocates so often come off as scolds, telling us that in this new economy we're going to have to make do with less, so we should all get used to buses. Then they try to tell us that buses are really just as good as trains. Yeah, right.

My daily commute involves two subway trains and a local bus. I also take express buses on a regular basis, and I'm a pretty frequent passenger on commuter trains and Amtrak. I'm intimately familiar with rail and buses, and all other things being equal I'd take a train over a bus any time.

Jarrett Walker has often cautioned us against using coincidental characteristics to judge buses and trains, and assuming they're universal intrinsic characteristics. For example, most buses operate in mixed traffic, and most trains operate in dedicated rights-of-way. Those trains, all else being equal, deliver more value than those buses, but a train operating in mixed traffic (often called a streetcar) delivers less value than a bus in a dedicated right-of-way (often called bus rapid transit), all else being equal.

I want to talk about a characteristic that I've observed in every bus trip I've taken but relatively few train trips. I believe bus professionals call it "ride quality," but I'll call it the Lurch, and I think anyone who's ridden a bus for any length of time knows what I'm talking about. Buses almost always have to change lanes. Unless there's a bus bulb, or they run in a curbside lane, local city buses have to do it at every stop. They also do it if they have to overtake another vehicle, or when preparing for a left turn across traffic.

This is a big deal for me and many others, including Adron Hall. I can get violent motion sickness, especially if I'm reading or writing or doing anything with any kind of computer. I get it in cars if someone else is driving, especially if I'm sitting in the back seat. I get it on buses and planes, but never on trains - with the single exception of the Acela Express. I get it most often on winding country roads, but I still get it on city streets, especially if the bus has to make a lot of turns.

I haven't taken any of the prototypical "BRT" systems in Curitiba, Bogota or Guangzhou, but all the pictures I've seen have space at some stations for the buses to pass each other, and that would cause a Lurch. Select Buses here in New York certainly do the Lurch. On the other hand, the rubber-tired subways of Paris and Montreal don't.

The only time you get a really strong lurch on a train is when the train changes tracks. One such switch that I know well are the one just east of the Times Square station on the #7 line, where trains can enter or leave either of the two terminal tracks. The other is just west of 75th Avenue on the Queens Boulevard, where F trains switch from the express track to the local track and back.

These switches can cause the train to lurch, but they're not Lurches. One big difference is that they're very predictable. I know almost exactly when the train will go over the switch before Times Square, and if I feel it I know that I need to stand by the doors on the right side of the train if I want to get out first. The train operators also know well in advance, and they usually slow down. Just when I was writing the last paragraph, in fact, I went over the switch at 75th Avenue and we didn't even lurch a little.

The big difference, I think, between a little lurch and a bus Lurch is predictability. Every train has a set of movements, but you can be confident that unless there is some extreme event (short stop, derailment, giant scorpion sting), those movements will not exceed a certain range. With buses, the range of possible movements is much bigger.

I mentioned this to Jarrett once, and he asked if it helped to have a low-floor bus. After a couple years' experience, I have to conclude that it doesn't. The movements may feel a bit different, but they're not significantly better. He has acknowledged this on his blog: "Ride quality in buses is improving, and guided busways may give buses an even more rail-like feel, but new rail systems will probably always have an advantage with their smoother running surface. Is the smooth ride of rail indispensible to a useful network? This can be a tough question whose answer may vary from one community to another."

Having lived in cities with all-bus networks, I definitely wouldn't say that the smooth ride of rail is indispensable, but it makes a big difference. As I said at the top, all other things being equal I'd choose a train over a bus any time, for that reason. And whenever a bus advocate tries to tell me that buses are just as good as trains only cheaper, I wonder: when was the last time that they felt the Lurch?


threestationsquare said...

I rode the O-Bahn guided busway in Adelaide and noticed that it genuinely didn't have "the Lurch". With all the dedicated infrastructure required, it's pretty hard to believe that a guided busway works out cheaper than a railway, but I guess it might be in situations where the dedicated segment is shared by a lot of lower-ridership routes (where it's not worth spending to eliminate Lurches on non-shared segments).

arcady said...

It's not just the big lurch, it's also all the small subtle back and forth steering that the driver does to keep the bus on the road. It's also an issue in terms of longitudinal acceleration, not just lateral: to keep a bus going at the right speed, there's a constant varying of power from the engine, as well as shifting of gears and so on. Trains, in particular urban electric trains, tend to accelerate at a nice smooth rate that rapidly increases from zero to a peak, then slowly drops off until the train reaches its top speed and then coasts until it's time to brake for the next station. Roads can also have a tendency to be bumpy, especially when they have heavy bus traffic. This makes the ride uncomfortable and makes the whole bus rattle, which makes the ride loud as well. That's an issue of maintenance, but it's often the case that the maintenance is done by someone entirely different from the bus operator, and there's nothing that the bus operator can do about it. Of course, a streetcar or railroad line in bad enough condition can also give a pretty poor ride quality, but generally, rail systems do tend to be in better shape than that. As for guided bus, I imagine that it eliminates all the steering issues, and generally makes for a pretty smooth ride, though maybe still a bit bumpier than rail (at least, that's been my experience with monorails).

BrianTH said...

I missed the earlier thread, but I do love my bus (the P71 in Pittsburgh). It picks up a block from my house, runs local for a bit more until it gets to the East Busway, then drives on the East Busway for an express trip to Downtown Pittsburgh, where both my wife and I work. I suppose if there was a train that did the exact same thing that might be preferable, but more realistically there would be a train line instead of the East Busway, and I would have to take a shuttle bus to that train and then transfer. I would not prefer that over my current service.

Incidentally, I can't read on buses because of these motion sickness issues. When on the Busway it is a bit better, but I suspect it would be much better on a train. That doesn't change my mind--I'd rather have no transfer and treat the bus as nap time or stare out the window time, as opposed to having to transfer but be able to read on the train part.

kantor said...

I suffer (badly) from motion sickness; to the point that even reading your description of the Lurch evoked memories that made me feel a little queasy.

If bus is the only option (which is invariably the case in the small Italian town where I live) I'd rather walk up to 2/3 km. If I do have to board a bus I'm always nervous; and I do not travel by car for more then five minutes unless I drive.

However I'm a terminal case; for instance my wife can do anything in a bus: read, watch a movie, eat and probably even aerobics without feeling any discomfort whatsoever.

But some time ago she had to go to Florence, where a new tramway opened a couple of years ago. And once back she went on forever, describing the quality and the smoothness of the ride. She was really fired up by the experience.

So even for people who do not fear the Lurch, riding the wheels is definitely a better experience. And this is exactly the reason why I'll never agree with Jarrett Walker (a real master on many other subjects) on the "interchangeability" of buses and trains.

Mike Hicks said...

Yeah, the difference between rail and bus service is night-and-day. It's got to be measurable with accelerometers and things like that. Heck, one huge difference between buses and trains (at least in the Twin Cities) is that wheelchairs need to be tied down on buses. On trains, the ride is smooth enough that they don't need it.

Now, there are rail lines out there that have poor ride quality. I remember lurching forward and backward quite a bit on the MBTA Green Line, and I even fell over the first time a PATH train pulled out when I visited New York -- though that was more an issue of a lack of nearby handhold than anything else.

Still, the motions of a train are typically much more constrained than those of buses. I'm kind of convinced that buses must have crummy suspensions for the most part, though it's probably a compromise since they typically have to deal with lots of bumps and potholes that basically never exist on rail lines (switches can cause bumps, though).

Bus rides are also made worse by the fact that street surfaces aren't flat -- there's usually a significant lean happening by the time a bus gets over to the curb lane, and I suspect the road camber is a significant contributor to lateral lurching.

I don't see it as often these days, but a bunch of buses I rode while in college had the strange behavior of leaning outward as the wheel was turned. On sharp turns, I think it easily hit 15 degrees even though the vehicle was only moving a few miles per hour. It got bad enough at some points that I'm sure those buses would occasionally strike signposts and light poles along the side of narrow streets. Another contributor to my theory that bus suspensions are generally poor.

Articulated buses have all sorts of other strange behaviors. I've often wondered if it would be smarter to put wheels under the articulated area, much like how TGV trains are built.

Anyway, a lot of the problems with buses could be alleviated by having well-maintained streets and using bulb-outs to reduce the need to weave side-to-side.

fbfree said...

I prefer a local bus over a in traffic streetcar (the Toronto experience). I have also been on busses where the driver has taken extra care to minimize lurching, and it made a big difference compared to other bus trips, especially on an artic packed with standees. Trains can still have significant lurch, especially on poor quality track or when train protection systems are over-relied upon (CTA Blue Line to O'Hare anyone?).

In conclusion, I will not always pick a train over a bus as driver and maintenance practices can make either bad. However, if ride quality is the only issue, a well maintained train with a good driver will always beat a well maintained bus with a good driver. (Of course frequency and reliability are still more important.)

Pragmatic Liberal said...

I ride a bus on the NJ Turnpike everyday. There is "lurch" no matter what, but there is a vast difference in the quality of the drivers. With some drivers, I can stand without the need to hold on, except to be prepared for emergencies, this includes when we change lanes and even have to take fairly sharp curves. On the other hand, with the driver I had this morning I had to hold every second. I didn't even want to let go to change pages in my book.

Matt Fisher said...

Besides Curitiba, Bogota and Guangzhou, don't forget Ottawa. What BrianTH argues is applicable to Ottawa: I hear some bus riders, would rather have a "one seat ride" to downtown from Kanata/Orleans/etc. via the Transitway over having to transfer. And with current light rail plans in Ottawa to replace the Transitway, some BRT boosters say that we should not go with LRT, instead wanting a bus tunnel and claiming we should "complete the Transitway", which they falsely claim is "the envy of the world". It is true, though, that Ottawa has a better transit mode share than most American cities.

busplanner said...

Cap'n - Sorry to hear you suffer from motion sickness. I agree that can be more of a problem on buses (though I have ridden trains on some awfully bad track for the speed.)

My "problem" is "The Squeal", the horrible screeching noise that occurs on tight rail curves, such as on PATH and in certain locations on the NYC Subway. My ears are supersensitive to that squealing frequency. (I acknowledge that the Jack Brakes on some buses and trucks are similarly a problem for me.)

Matt Fisher said...

I should have added, Kanata is also the home of Scotiabank Place, the arena that is home to our NHL franchise, the Ottawa Senators, and we Canadians are ever so mad about (F.Y.I., IT'S NOT PRONOUNCED "A-BOOT"!!!) hockey. I'm not much a sports fan, but I will say this is especially apparent when the Senators are in the Stanley Cup playoffs and we are currently up against, yes, the New York Rangers.

And yes, as I said in another post, don't hate me for being satisfied with riding OC Transpo buses. It's no big deal to ride "the bus" in Ottawa.