When four lanes are two

Mass. Ave FDR

One of the most interesting bits in Arlington’s plan to rebuild Mass. Ave. is a discussion of how drivers actually behave today, and would be likely to behave under new road designs.

It turns out that you can’t just draw lines on asphalt, post signs, and expect people to do what you say.

Drivers decide how fast to drive, and even where on the road to drive, based on the physical conditions and cues they encounter en route.

On page 34, the Functional Design Report filed by the Town describes what happens today when motorists pass bicyclists:

Based on actual field observations, significantly more vehicles passing bicycles on the left encroach into an adjacent travel path from a wide lane shared use facility compared with a dedicated bike lane facility.

That squares with my experience both as a driver and as a cyclist. Traffic is generally so light on Mass. Ave. that a driver can give a cyclist plenty of room when passing. In effect, Mass. Ave. switches from two lanes to one, then back to two, as the driver “encroaches.”

This flexibility, which manifests itself at other times too, is probably aided by the lack of individual lane markings on Mass. Ave. But what happens when the lanes are marked, as the Town (and everyone else) proposes?

Under the Town’s proposed design, bicycles would have their own dedicated lanes, so the issue does not arise. The bike lanes have enraged some people, however, so the FDR also examines a four-lane configuration. Among its conclusions:

In the particular case of the Massachusetts Avenue corridor…the continual practice of encroaching into an adjacent travel path to pass bicyclists implies that a marked four-lane facility would actually operate more like a three lane facility since there would be insufficient space available for a second vehicle traveling in the same direction….

Most likely, vehicles traveling in the same direction would need to be traveling in a staggered fashion to avoid conflicts. (p. 34)

“Staggered fashion” describes cars that follow each other, rather than travel next to one another, due to lack of room. In other words, a de facto single lane.

There’s a bit more—worth reading—about how the presence of parked cars on the street exacerbates this tendency. The FDR (download it here) concludes that the actual behavior of traffic under the four-lane design is not very different from the three-lane configuration proposed by the Town.

Striping the lanes, which everyone seems to want to do, makes today’s informal two-lane-one-lane-two lane behavior more problematic. Cars and bikes, who today share a 24-foot superlane, will instead be sorted into much narrower slots.

The Town’s solution is to provide a “slot” for everyone, including marked bicycle lanes.

A plan with four marked traffic lanes that are shared, however, means that to ride safely bicycles must often obstruct traffic in the right-hand lane—they must stay a safe distance from the doors of parked cars, while passing cars must stay a safe distance from the cyclists.

What distances are we talking about? A cyclist probably occupies three feet of road width, considering the need to avoid potholes and other things even while traveling in a straight line, and state law requires drivers not to pass cyclists unless they can do so with three feet of clearance.

Depending on the width of the parking lanes, cyclists need to be a couple of feet away from the doors. Indeed, cyclists are allowed—and advised—to “take a lane” by riding in the center of the lane if insufficient width makes traveling along the right side unsafe.

My view: This would not be a satisfactory solution for anyone.

As a cyclist who is comfortable riding on Mass. Ave. as it is, I see the proposed bicycle lanes as potentially constraining. (Other cyclists may feel differently.)

On the other hand, bike lanes simplify things for drivers, who will be able to just cruise straight down their “slots” without having to do that little dance to pass bicycles. If we are going to get rid of the superlane, I think having bike lanes is the way to go.

The main beneficiaries of the new design are pedestrians, who have safer and shorter crossings. I think that is entirely appropriate. If the price of that improvement is a little less flexibility for me, it is worth it.

Update: See also When Four Lanes Won’t Fit, about the rest of the Town’s analysis of a four-lane design.

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20 comments so far

  1. dr2chase on

    I think you need to be more explicit about the distance implied by “a couple of feet from the door”. I can’t find the video (just went looking), but there is one that does a good job of justifying five feet from the car, six to be comfortable. And the non-bikers reading this need to know that this applies to every parked car, because it’s hard to be certain that there isn’t someone in the car about to open the door.

    And as long as we are kowtowing to enraged people, well heck, I guess I’ll be enraged too, just so I can get some special attention to my pet peeves. Here’s my pet peeve. Compare Groningen, Netherlands, to the combination of Cambridge, Somerville, and the flatlands of their adjoining towns (Medford, Arlington, Belmont Watertown). Similar (somewhat) weather, similar demographics, similar populations. We’re denser. They’ve got the 57% ride share (and the facilities to make it happen). Wouldn’t it be nice to not hassle with parking or traffic when heading in to Cambridge? I’m “enraged” that we don’t have that, and this proposed rebuild of Mass Ave. is inadequately biased towards my desires (which I think I even managed to kinda-sorta justify with numbers).

    Because seriously, the bicycle accommodations in the proposed design are not adequate to get a bunch of new people riding bicycles. Riding in a door lane is not that fun. You want change, you want something that works, look at what was done in the Netherlands, and copy that.

    • Adam Auster on

      DR: I am sure I should be more explicit about many things. There is much more in the FDR about accommodating bicycles on Mass. Ave., especially in light of on-street parking. Just trying to digest and distill some of that into a smaller bite, always hard to do well.

      You are right that the proposed design—the 3-lane-with-bike-lanes design, not the unworkable 4-lane one—won’t get people out of their cars, at least not much. That was never one of the goals, for better or worse.

      Instead the plan accommodates the users we have already (drivers, pedestrians, cyclists); it is conservative, not transformative.

      The main thrust of the design makes things safer for pedestrians, which is badly needed. It does so while making things modestly better for drivers and perhaps slightly more constrained for cyclists (or perhaps not, it is probably a wash).

      • dr2chase on

        I think conservative is a mistake, but oh well. Paint is cheap, if things need to change.

        Have you seen John Pucher’s Cycling for Everyone presentation?

        • Adam Auster on

          DR, conservative was in the cards when the Town hired FST for this job. As you note, the design is not exactly cutting-edge.

          To be fair, the consulting engineers do have to work within many constraints.

          If the Town hoped to avoid controversy by playing it safe, it hasn’t exactly worked out that way.

  2. Ray Jones on

    If you’re comfortable riding a bike on Mass. Ave., you must have a pretty good suspension. I’ve found I avoid it not because of traffic, but because of how horrible the surface has become. Unfortunately, the right lane is the worst (heading into Cambridge), basically forcing cyclists to ride even farther to the left than usual.

    • dr2chase on

      Long steel bike, fat tires, lightly sprung saddle. Rode it last Friday from Pleasant up into Lexington because the MM trail had not been adequately plowed then (not sure how it is now). Also, good lights, so I can see hazards in the dark.

      Before the fat tires, I rumpled the edge of a hand-buit rim in Belmont, so yes, I do understand.

      Crappy roads is one of the problems with “sharing” — busses and trucks put cracks into the roads, and then cars finish the job on wet days. (What I read is that road wear is proportional to the 4th power of tire weight, but I think that is assuming that the roads get repaired as soon as they crack.) One way to deal with this is to build a thicker road; is that in the cards here?

      • Adam Auster on

        Re thickness: I do not see that addressed in the FDR, so I conclude this is an issue for a subsequent design phase.

        I can tell you that the pavement at issue is just the top asphalt layer or layers; unlike some recent road projects (e.g. Summer St. in Arlington, Somerville Ave. in Somerville) the underlying concrete layer will not be touched.

    • Adam Auster on

      Ray, I do have a steel frame, but of course you are right.

      To be 100% truthful, I should have said that I am comfortable riding outbound, where the road surface seems to be much better than inbound. (I have no idea why but it is so. Have you noticed this?)

      I usually take the Minuteman inbound, despite the detour, for exactly this reason.

      A smooth road is probably the real bike amenity associated with this project.

      I just thought this was TMI for this post, where I wanted to focus on the Functional Design Report and the metrics issues.

      • Ray Jones on

        I have noticed that it does seem nicer outbound than inbound (but it’s been some months since I was out on it). Part of this might be perceptual rather than actual; because outbound traffic is so much lighter, one does not feel constrained to bike in the bad parts to avoid cars.

        • dr2chase on

          It could be a lot of things — if the trucks/busses are more loaded inbound than outbound, it could be that (my brother, in FL, reports that trucks TO Miami are consistently heavier than trucks FROM Miami, with the result that the two directions of I-75 are repaved at different rates).

          Possibly different drainage under or on the street — if one side drains towards, the other away, you’ll get one half wetter. Wet is bad for roads, good for potholes. Could even be that the inbound (southern-ish) side is more shaded, hence it takes a little longer to dry out.

  3. Mark Kaepplein on

    My observations match those in the DCR – cyclists are currently given more room by motorists now then if the plan is executed. Its good that cars are not side by side, that allows room for drivers to move over in any situation.

    Painted lanes make users into owners who don’t think to or want to give up their territory. Currently drivers are more aware of all the other users and work out accomodation. With marked lanes, drivers ignore what is not directly ahead of them in their lane… more than usual.

    Its all why shared space design in Europe works so well – everyone has to pay attention, be aware of each other, and work out conflicts. Roundabouts force attention. Signaled intersections are infamous for inattentive drivers going through red lights when they don’t see a car stopped in front of them or cross traffic.

    I suspect inbound buses are heavier as work starting time is more uniform than ending time. The evening rush “hour” is longer and more spread out. BTW, check out the Federal Transit Database. For 2009, MBTA buses get 14% worse diesel fuel milage than 2005, and cost per passenger mile is now about $1.35. That’s almost 3x IRS milage deduction.

    Paint hastens road cracking, and lack of distributes wear better on the roadway, within “lanes” and having two each way. The town has been lame in not filling cracks, so water gets into the substrate. The substrate becomes more fluid, shifts more, so pavement shifts more under load leading to cracks. In winter, the water freezes and expands.

    • Adam Auster on

      Both sides in this debate have called for marking the amorphous “superlane” into discrete lanes.

      The claim that the superlane has some advantages strikes me as credible, and also as a very “Mark Kaepplein” argument—counter-intuitive and against the conventional wisdom.

      It is not self-evident to me that marking the lanes is beneficial to drivers or cyclists.

      However, the Town’s plan, marked lanes and all, confers tangible safety benefits to pedestrians, shortening crossing distances dramatically while improving visibility.

      Maybe you could do this without marking some of the lanes, but it’s not clear to me how.

      That’s why cyclists like me should accept this design, despite the potential for a slight constraint, as I said in my comments above.

      Motorists, too.

      PS Mark, I think you mean “FDR” for “Functional Design Report,” not DCR. (The DCR is the state agency that is building the path along the Alewife Brook her in East Arlington.)

      • Mark Kaepplein on

        OK, here is another counter-intuitive fact supporting my proposal for a little chaos:

        Many studies found marking a crosswalk (alone) increased the number of pedestrian injuries and deaths. My hypothesis is that the illusion of increased safety made pedestrians less observant and cautious. They paid less attention, hence, some chaos needed. BTW, the most effective treatment to increase pedestrian safety? Raised medians and refuge islands, the former being better as pedestrians frequently cross outside intersections. Cambridge has a 5 foot wide raised median, Arlington plan is two 5 foot wide bike lanes.

        • dr2chase on

          It seems to me that the drivers ought to be observant and cautious, since it’s the cars that present the danger. You are right, it will reduce accidents if the pedestrians are more careful, but why is it their responsibility to do this, when it is the cars that do the hitting? If I (a big guy) go plowing through a crowd, trampling on feet and knocking people off balance, I think everyone would agree it was my fault, and not the fault of the people who were so incautious as to be in my way.

          We have a chaotic intersection in Belmont, and pedestrians observe it, and cautiously find someplace else to cross. Why should we inconvenience the harmless people?

          • Mark Kaepplein on

            Last week a woman stabbed her boyfriend, killing him after seeing a hickey on him. Is domestic violence always the man’s fault? No. Size has nothing to do with it. If a small person darted into a larger person, the former is still at fault even if the second was in (predictable) motion. Also the small person’s fault for walking in front of runners or cyclists – that’s a closer example to crossing in front of a motorist. Another example is the viral video of a woman walking into a shopping mall water fountain while texting. Fountain’s fault? She’s suing.

            BTW, pedestrians are less likely to “see” motorcycles, and walk in front of them. The prevailing attitude is still that motorcyclists are always at fault for any crash, just for getting on one, much like your’s towards motorists vs. pedestrian.

            The pedestrian safety overview I read is on Arlington’s web site, transit board references. Quite often the pedestrian is at fault and often drunk. Darkness is a big factor for peds and cyclists. Dark clothing further reduces visibility. Drivers didn’t choose the clothing. Road design can’t always beat Darwin (natural selection).

            Let’s outlaw low-visibility vehicle colors like silver-gray! Advocate high visibility yellow-green and orange! People almost never choose color based on safety. Popular clothing and car color choices are often the least safe here. Vibrant colors are more popular outside the US.

            • dr2chase on

              I completely disagree.

              First, if you are driving, you have a duty to avoid collisions. If you see a pedestrian, you can adjust your behavior to account for the possibility that they will cross the road, or not. You can, by not slowing, put yourself in a situation where it is impossible to avoid a subsequent collision if the pedestrian steps in front of you, but it was your choice to be in that situation. People talk about driving cars as if they were riding some wild animal bareback, and that’s just nonsense. You can always slow down or stop.

              Second, one difficulty with crosswalks, is simply that cars do not stop for pedestrians in crosswalks, or, when they cannot see the entire crosswalk, drive as if there was no pedestrian in the part they cannot see, instead of driving as if there might be. The law is completely unambiguous here — cars stop for pedestrians in crosswalks. Drivers like to assume that the pedestrian will give way, and don’t slow down. And of course the pedestrians give way, because getting hit by a car hurts.

              Third, there is a difference between walking into an immobile fountain, and walking into a road. You can always stop your car; if a pedestrian walks into an immobile car, that is clearly the pedestrian’s fault, but if you are that close to a pedestrian and not immobile, then it is your fault.

              Note that there is no legal requirement that pedestrians dress in blaze orange. I manage to spot pedestrians on the bike path by reflective piping on their shoes, jackets, or backpacks, and sometimes by the reflection of their dogs’ eyes. It merely requires that one pay attention. I expect no less of people driving cars (especially since the cars outweigh me by a factor of 10 and roll much more quickly — they’re that much more dangerous, and should take that much more care). If someone is not willing to take that much care operating a piece of heavy machinery, I suggest they walk, bike, take a bus, or a cab.

              It’s just not that hard. All you have to do is slow down, and sometimes stop.

              • Mark Kaepplein on

                If a car or pedestrian crosses in front of a train or a pedestrian stumbles off a train platform, is the conductor at fault for not stopping his big, heavy vehicle to avoid the crash? Is the manufacturer at fault for having weak brakes? Should trains not exceed 10mph near all crossings in case some bone head crosses in front, or does that only encourage people to try and beat the train? Like the train, the car driver is usually taking a predictable path. Car-ped turning impacts are less frequent than forward driving cars.

                People are free to be right and dead if they choose. Reducing that attitude is a win for the gene pool. Caution and awareness isn’t the sole responsibility of motorists. Cops, firemen, and highway workers have high visibility jackets for good reason. Sneeker and backpack makers are more responsible than most pedestrians in giving few choices without reflective markings – most people don’t seek them out.

                I see three situations where motorists don’t stop for pedestrians. First, like red lights, they weren’t paying attention. Second, the pedestrian seemed to be waiting and yielding to motorists, waiting for a safe lull. Third, drivers not thinking that the monster SUV driver in the next lane stopped for some reason, after all, he is not directly ahead affecting him. Its the tunnel vision that defined positions (lanes) create.

              • dr2chase on

                The train analogy is flawed; consider that railroad tracks are protected from easy crossings, and the crossings themselves are well-marked, often with bells and gates. Crossings are often grade-separated to remove danger.

                And, trains are physically unable to stop and start quickly; it would be an extraordinary impediment for them to stop at intersections. Cars, on the other hand, can stop and start quite quickly.

        • Adam Auster on

          Mark, I am familiar with studies that suggest that unsignalized intersections across wide streets are unsafe. The wider the crossing distances, the less safe.

          Partly this is because of the risk of multiple-lane-threat crashes, since multilane streets are wider.

          I do not find this especially counter-intuitive, and it is a strong argument for the Town’s design, which shortens these crossing distances dramatically.

          Raised medians were nixed by the fire chief (who approves the current plan), but there are two pedestrian refuges in the design, and the other crossings are improved.

          • Mark Kaepplein on

            I suspect the fire chief objected to having one traffic lane AND refuges. With only one traffic lane, drivers have little room to pull over for responders. I don’t see how he could object to four lanes with refuge islands where width allows.

            If this isn’t another deception, the fire chief needed convincing instead of hijacking the design. Opticom(TM) which changes the traffic lights to green releases traffic clogs and the need to drive on the wrong side of the street.

            Pedestrian refuge islands exist in the center. Has he found them to be a problem? Can some aspect of them be fixed? The plants and pavers are not pedestrian friendly. Refuges cut crossing distance in half, while curb estensions provide no protection – pedestrians are already well protected by parked cars plus the door zone.

            An example of a safe, wide, 4 lane urban street with refuge is on Washington Street, Boston. Tufts/New England Medical Center on one side, Orange line stop, parking, and the theater district on the other. Despite low traffic volumes, the emergency vehicle access, frequent standing vehicles, and lack of cyclists demanding bike lanes must have defeated compulsions to narrow the road.


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