Friday, May 1, 2015

Bus Lanes on the Harvard Bridge

April was Bus Month here at Amateur Planner, and May is showing no signs of slowing down. I noticed recently that in a traffic jam on the Harvard Bridge (which occur regularly, especially during baseball season), there are not many buses on the bridge, but they carry a large portion of the people crossing it. So I waited for the next traffic jam on the bridge (not a long wait) and went to take a photograph, which I then annotated:

This was taken at the 250 Smoot marker (so about two thirds of the way to hell), and I noted that, in stopped traffic, there were 20 cars per 100 Smoots (this is a bit more than 25 feet per car; Smoot markers make it really easy to quickly measure things). I took a quick census of the number of people in each car (appeared to be about 1.3) and set about making the graphic above. (The bus numbers account for one at all-seated capacity, one at normal standing capacity, and one at crush load.)

Then I tweeted it, and it may have gotten retweeted a couple of times.

There was one bizarre (in my opinion—and I'm really not sure if it's uninformed or malicious) response thread, which amounted to the following (as requested by the Tweeter, the full conversation is below):
This is where the bus does go. (1/4 and
1/2 mile buffers of MBTA bus routes.)
So, pretty much everywhere.
Responder: Plenty of people need to get where buses don't go.
Me: I'm fine with them having one lane of the Harvard Bridge, and the buses go a *lot* of places; if they ran faster than cars, more people would take them.
Responder: So glad you're not making the rules.
Me: Here are areas within 1/4 and 1/2 miles of bus routes, where again are people going that the buses don't go? [See map at right.] And why should my tax $$ go to pay for buses to sit in traffic so cars can … sit in traffic? >50% of the people on the bridge are in buses. Why not give them 50% of the space?
Responder: It's the when, not the where. Bus schedules don't nec. match ppl's schedules. RedSox fans all over NE. [editor's note: see original Tweet in thread.]
Me: So if the buses were 15 minutes faster than driving, people would take them, and anyone who *drives* to Fenway deserves a dope slap. [There's] plenty of parking at Alewife-Riverside-Wellington-Wonderland. Trains run every 5 mins. Why should 20k+ bus passengers be delayed 10 mins for a few Sox fans?
Responder: It's about making connections too—when too many connections get inefficient, driving works.
Me: Driving works? Tell that to the people on that bridge: people were walking faster. Bus lanes means more people opt for transit, fewer cars overall, and less traffic.
Responder: Just because buses work for you doesn't mean they work for all.
Me: That's the problem. They don't work. The deck is stacked in favor of driving. I'm not saying ban cars, I'm saying let's equalize street real estate. Why shouldn't a bus with 50 passengers have priority over a car with 1 or 2?
But this is the usual reactionary inability to see the greater good. Take away a lane from cars, and it's an affront to driving. An affront to freedom. Un-American. Never mind the majority of people on that bridge aren't driving cars. They don't matter. Still, I haven't heard this turned in to an equity argument, so that's kind of groundbreaking.

So the first part of this blog post is a plea: Ms. Cahill, I want to know what goes through the mind of someone who can't see that transit efficiency is a societal benefit, and that it will amount to more people using fewer vehicles. Please email me, comment here, and discuss. I want to know.

The second part is me, trying to quantify what would happen to vehicles displaced by a bus lane on the Harvard Bridge, and what the time savings would be for bus riders as opposed to the time penalties for drivers. And, as I am wont to do, I did this in chart form. I imagined a hypothetical traffic jam stretching across the bridge (0.4 miles) in a closed system where all of the cars feed off of Mass Ave on to the bridge (this is close to the case, but some traffic does enter from Memorial Drive):

At first glance, going from two lanes to one would double the length of roadway needed to store the same amount of cars. But several other factors come in to play. First of all, the buses take up the space of 8 cars—at least. Then, we can assume that 10% of the cars remaining will shift modes: if taking the bus is all of the sudden significantly faster than driving, people will use it. And people in taxis (by my estimation, 10% of the traffic on the bridge) will likely switch in greater numbers since they're starting closer by: I estimated 50% mode switch there. Then there's induced demand: make the traffic on Mass Ave worse, and some drivers—I said 10%—will choose another route, whether it's the Longfellow or the BU Bridge or further afield.

Add these together, and I would guess that traffic would increase by between 1/3 and 1/2. Assuming that traffic moves at 5 mph, this would mean an increase of 2.5 to 4 minutes for each person in a car on the bridge. But it would also mean that buses would cross unencumbered by traffic, making the trip in one minute, and saving every bus passenger 7 (this assumes that the bus lanes extend back to Vassar Street, displacing bus stops and a few parking spaces on Mass Ave through MIT). With these numbers, drivers would incur 510 minutes of additional delay, but bus passengers would save nearly three times that much time—a dramatic benefit.

Am I way off base with these numbers? I don't think so. When the Longfellow went from two lanes to one, vehicle traffic decreased by nearly half! Traffic spread to other locations, people chose other modes (walking, biking, transit), or didn't make trips. The traffic apocalypse that was predicted didn't materialize, and life has gone on.

The Harvard Bridge is one of the most heavily-traveled bus corridors in the city, up there with the North Washington Bridge, the Silver Line on Washington Street, the 39/66 concurrency on South Huntington, portions of Blue Hill Avenue, some streets to Dudley and the feeder buses to Forest Hills. (All of these should have bus lanes, by the way.) The 1 and CT1 combine for more than 15,000 trips per day and, at rush hour, better than one bus every 6 minutes. The bridge also carries the heavily-traveled M2 MASCO shuttle 6 times per hour. Combined, these routes account for a full (usually crush-load) bus every three minutes—which is why in a 10 or 12 minute traffic jam there are three or four buses on the bridge at any given time—transporting at least 1000 passengers per hour.

Bus lanes would allow these bus lines to operate more reliably, more efficiently and more quickly, meaning the same number of buses could run more trips, and carry more people. Which, if they're 10 minutes faster than cars, they're going to be carrying! This would be something that could be tested and quantified, and it could be done as a temporary pilot with cones and paint. There is no parking to worry about, no bus stops to relocate: just set aside one lane for buses (and give buses signal priority at either end of the bridge). This would take the cooperation of MassDOT, DCR, Boston and Cambridge—and prioritize "those people" riding transit over real, taxpaying non-socialist Americans—so I don't expect it to happen any time soon.


  1. My one question is why you'd limit the bus lanes to just the Harvard Bridge. As far as I know, there's no bus service that uses it that doesn't use Mass Ave at least as far as Central Square in Cambridge and Symphony in Boston, and my experience has been that that whole section of Mass Ave is entirely stationary much of the time at rush hour. It seems to me that if you're going to put bus lanes in at all, you'd at least want them to run from Central to Hynes, since that's the most used part of the 1 route, due to people trying to avoid going through downtown to get from Cambridge to Back Bay and points west..

    1. You certainly don't have to. Once you get in to city streets, you have to deal with traffic and parking and the like. But I agree, bus lanes should stretch from Central to Columbus, at least! The 1 is such an important link between Red-Green-Orange-Silver (and if extended to Andrew, Red again) that it could probably run a 60 foot bus every 5 minutes if it operated reliably at twice the speed it does right now in traffic.

    2. If straightening out the 1 and eliminating the segment to Dudley, why not go to the JFK / UMass red / purple station and terminate at the UMass campus instead of Andrew?

  2. I'm not convinced that the second car lane on the bridge actually benefits anyone at all. In freely flowing conditions, one lane is almost certainly enough traffic to saturate the many intersections with traffic lights on either side of the bridge, and when those hit saturation, the second lane is mostly just used to store the queue of cars. And even in free flow conditions, it just helps cars get to the red light faster.

    On a somewhat related note, I kind of wonder if anyone has tried to apply the many things that the designers of the internet learned about congestion control to road congestion. Things like avoiding excessive queueing or trying to control congestion further upstream from the chokepoint.

  3. BU bridge is far more congested than the Harvard Bridge (also the 47 bus route, btw) - something that could be solved if Brookline, Boston, Cambridge, and the state would get together and make that whole mess a bunch of normal intersections and two-way streets.

    as for the Forest Hills feeder buses - extending the orange line down to roslindale would solve the issue of NINE bus lines sharing a single mile, highly congested, stretch of Washington Street - unfortunately the MBTA refuses to acknowledge that this single stretch of road likely has among the highest bus ridership in the entire system, and the city doesn't seem interested in improving this stretch of street (you can see the pavement warping in some spots as the result of literally 1000 buses stopping there a day). As far as capital projects go, one stop would be relatively cheap and after reconfiguring some lines to dead head at Roslindale (and extend the 39 down to Roslindale Square) - would probably end up saving the T money in operating costs. This is an important project for many other reasons, but if Baker is serious about looking for ways to reduce operating costs, they really need to think strategically about how they can use capital improvements to reduce redundancies and congestion within their own system.

    1. I'm pretty sure the thousands of cars on Washington Street play a role in warping that pavement.

      As far as congestion goes, I've only ever seen it congested during rush hour, when all those cars are trying to get out of the city. At 9:00 pm there are practically no cars on the road and the buses go through Roslindale Sq every five minutes.

      Extending the OL to West Roxbury, though, would actually remove the need for most of the routes and the buses could be redeployed to make other routes more frequent.

    2. Orange Line to West Roxbury is probably a good idea, but to make it work well, it probably should be constructed simultaneously with a D2 green line branch to Needham, so that the need for Needham Line commuter rail service goes away entirely (possibly eliminating Hersey and Needham Junction). The capacity of the Green Line tunnels may make that problematic. On the other hand, it would reduce demand for commuter rail platforms at South Station, which might be helpful if the T is going to continue to pretend that each track at South Station can handle only half the trains per hour that NJT was planning for ARC.

  4. Ari, I would have appreciated you quoting my tweets directly instead of paraphrasing them. Rather than having bus lanes, maybe certain streets in Boston/Cambridge could have congestion pricing so that private drivers might have less of an incentive to drive in unless they need to. I'm not against buses getting where they need to go, but your condescending tweets and blog entries won't get you many allies.

    1. You want me to quote the entirety of the conversation? Sure? Because if you want to talk about condescending, Tweets like this are a good start.

      As for congestion pricing, it really only works if you have better transit. Right now, the "price" paid for congestion is paid for everyone sitting in traffic (there's an economic loss to that). If you gave transit users a less congested option, as noted above, more people would use it, because it would be faster. This would reduce the overall demand for cars on the road, and reduce traffic for the people who did need to drive.

      So again, I really want to know why this would be a bad idea.

  5. In my experience, people who are against taking away space from cars and giving it to transit are people who personally cannot see themselves ever using that transit. The fallacy in that logic is that less space for cars = slower travel times for cars. If transit is made better and more efficient, a certain number of people currently in cars would switch to transit, therefore making travel times BETTER for those who still choose to or have no choice but to drive. That last bit requires too much of a leap of faith for many people. It's the same resistance I've noticed to taking away space for bike lanes or cycle tracks. Fewer lanes for cars often results in faster travel times for everyone, but that just counter-intuitive enough for a lot of people that they simply can't believe it.

  6. Regarding the Mass Ave Bridge, I think it backs up as much as it does because the lane configuration of Mass Ave in Boston is so dysfunctional. It's mainly two through lanes in each direction, but the unprotected left turns and lane shifts (that people don't actually follow) just jam things up. Because of the lack of protected left turn signals and lack of dedicated left turn lanes, many signals have staggered greens, which are terribly inefficient. A single through lane in each direction with protected turn lanes where appropriate would do a lot to rationalize things.

    1. A single lane with protected lefts that also functioned as straight lanes for buses. Follow me on this:

      Bus lane comes off of bridge, and past Beacon was signed as "buses and left turns only." It would operate on a regular cycle for left turns unless a bus was detected in the lane (transit signal priority) in which case it would also display a green transit light (or perhaps a straight-up-and-down-like-Beacon-Street tram-style signal) would allow the bus to go straight ahead (and disallow other turns) at which point it would be a bus only lane until the next light. There would have to be safety-zone-style island boarding platforms as well (unless you buy left-boarding buses, which cost) but only at Beacon and Hynes, which could both be offset after the signal to allow buses to get through to the stop and the left turns to proceed after. But considering that buses carry half of the people on this route, they ought to be given half the street real estate (because better-functioning buses could carry many more).

  7. I am all in favor of limiting lanes for cars, one way or another, but according the information I could get my hands on, the buses are not good for the roads. Plenty of weight concentrated onto not many tires means results in lots of damage (because road damage by a wheel is proportional to cube of weight on wheel).

    Me, I bike. I pass a mess of cars every day at rush hour, and I'd pass more if they didn't so often take up the whole lane.

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