Thursday, June 20, 2013

Longfellow Bike Count

One of the issues I've touched on in the Longfellow Bridge series is the fact that there as no bicycle count done at peak use times—inbound in the morning. The state's report from 2011 (PDF) counted bicyclists in the evening, and shows only about 100 cyclists crossing the bridge in two hours. Anecdotally, I know it's way more than that. At peak times, when 10 to 20 cyclists jam up the bike lane at each light cycle, it means that 250 to 500 or more cyclists are crossing the bridge each hour. So these numbers, and bridge plans based on them, make me angry.

But instead of getting mad, I got even. I did my own guerrilla traffic count. On Wednesday morning, when it was about 60 degrees and sunny, I went out with a computer, six hours of battery life and an Excel spreadsheet and started entering data. For every vehicle or person—bike, train, pedestrian and car—I typed a key, created a timestamp, and got 2250 data points from 7:20 to 9:20 a.m. Why 7:20 to 9:20? Because I got there at 7:20 and wanted two hours of data. Pay me to do this and you'll get less arbitrary times.

But I think it's good data! First of all, the bikes. In two hours of counting, I counted 463 bicyclists crossing the Longfellow Bridge. That's right, counting just inbound bicyclists, I saw more cyclists cross the Longfellow in one direction than any MassDOT survey saw in both directions. The peak single hour for cyclists was from 8:12 to 9:12, during which time 267 cyclists crossed the bridge—an average of one every 13.4 seconds. So, yes, cyclists have been undercounted in official counts.

Are we Market Street in San Francisco? Not yet. Of course, Market Street—also with transit in the center—is closed to cars. [Edit: Market Street is partially closed to private vehicles, with plans being discussed for further closures.] And at the bottom of a hill, it's a catchment zone for pretty much everyone coming out of the heights. They measured 1000 bikes in an hour (with a digital sensor, wow!), but that was on Bike to Work Day; recent data show somewhat fewer cyclists (but still a lot).

I also counted vehicles (1555 over two hours; 700 to 800 per hour, including three State Troopers and one VW with ribbons attached that passed by twice), inbound pedestrians (about 100, evenly split between joggers and walkers, although there were more joggers early on; I guess people had to get home, shower and go to work) and even inbound Red Line trains (30, with an average headway of 4:10 and a standard deviation of 1:50). I didn't count outbound pedestrians, or the exact number of people I saw stopping to take pictures (at least three on my little nook of the bridge).

But did you come here for boring paragraphs? No, you came for charts! Yay charts! (Also, yay blogging at 11:20 p.m. when I should be fast asleep. Click to enlarge.)

First, bikes. Cyclists crossing the bridge started out somewhat slow—the moving average for the first 20 minutes was only one or two per minute. But the number of cyclists peaks around 8:40—people going in to the city for a 9:00 start—before tapering off after 9. I've written before about seeing up to 18 people in line at Charles Circle which is backed up by these data; the highest single minute saw 11 cyclists, and there were four consecutive minutes during which 36 bikes passed. At nearly 6 bikes per minute for the highest half hour, it equates to nearly 360 bikes per hour—or 10 per 100 second light cycle. Too bad we're all squeezed in to that one little lane. (Oh, here's a proposal to fix that.) If anything, these numbers might be low—the roads were still damp from the overnight rain early this morning.

What was interesting is how few Hubway bikes made it across the bridge—only 25, or about 6% of the total. With stations in Cambridge and Somerville, it seems like there is a large untapped market for Hubway commuters to come across the bridge. There are certainly enough bikes in Kendall for a small army to take in to town.

Next, cars. The official Longfellow traffic counts show about 700 cars per hour, which is right about what my data show. What's interesting is that there are two peaks. One is right around 8:00, and a second is between 8:30 and 9:00. I wonder if this would smooth out over time, or if there is a pronounced difference in the vehicular use of the bridge during these times. In any case, 700 vehicles per minute is not enough that it would fill two lanes even to the top of the bridge, so the second lane—at this time of day, anyway—is not necessary on the Cambridge side.

I also tracked foot traffic. I did my best to discern joggers and runners from commuters. Joggers started out strong early, but dwindled in number, while commuters—in ties and with backpacks and briefcases—came by about once every minute. I was only counting inbound pedestrians, and there were assuredly more going out to Kendall. Additionally, I was on the subpar, very-narrow sidewalked side; the downstream sidewalk is twice the width (although both will be widened as part of the bridge reconstruction).

And I counted when the trains came by. In the time that 2500 bikes, pedestrians and cars crossed the bridge, 30 trains also did. Of course, these were each carrying 500 to 1200 people, so they probably accounted for 25,000 people across the bridge, ten times what the rest of the bridge carried. Efficiency! The train times are interesting. The average headway is 4:10, with a standard deviation of 1:58. However, about half of the headways are clustered between 2 and 3 minutes. That's good! The problem is that the rest are spread out, anywhere from 3:30 to 8:30! Sixteen trains came between 7:20 and 8:20, but only 14 during the busier 8:20 to 9:20 timeframe. I wonder if this is due to crowding, or just due to poor dispatch—or a combination of both.

In any case, what Red Line commuter hasn't inexplicably sat on a stationary train climbing the Longfellow out of Kendall? Well, after watching for two hours, I have an answer for why this happens!  It is—uh—I was lying. I have no idea. But I say no fewer than a half dozen trains sit at that signal—and not only when there was a train just ahead—for a few seconds or even a couple infuriating minutes. I was glad I wasn't aboard.

Finally, we can compare the number of bikes as a percentage of the number of cars crossing the bridge each minute. Overall, there were 30% as many bikes as cars. But seven minutes out of the two hours, there were more bikes across the bridge than vehicles. Cars—due to the traffic lights—tend to come in waves, so there's more volatility. Although bikes travel in packs, too. Anyway, this doesn't tell us much, it's just a bunch of lines. But it's fun.

Tuesday, June 18, 2013

Is a part-time bike lane appropriate for the Longfellow?

So far in our irregular series on the Longfellow Bridge we've looked at the difficulty accessing the bridge from the south, the usage of the bridge compared to the real estate for each use and how many bikes are actually using the bridge at morning rush. While my next step is to actually go out and count bikes (maybe this Thursday!), I've been thinking about what sort of better inbound bicycle infrastructure could be implemented for the bridge.

Here's a graphic. I'll make more sense of it below (Click to enlarge):

Here are the issues at hand:
  • Peak bicycling occurs between 7:30 and 9:00 a.m., when bicyclists traveling from Cambridge, Somerville, Arlington and beyond converge on the Longfellow to commute to work in downtown Boston. For nearly any destination in Back Bay and Downtown, it is by far the easiest access.
  • There is much less cycling outbound at rush hour because of mazes of one-way streets combined with heavy vehicular traffic on the other access roads (i.e. Cambridge Street).
  • Thus, the highest bicycle use at any time on the bridge is during the morning rush hour inbound, but while plans indicate a wide, buffered bike lane going outbound, the inbound lane will barely be widened.
  • Since the bridge has a noticeable incline from the Cambridge side, there is a wide spread of cyclist speeds, and it is reasonable to expect cyclists to want to overtake during heavier use times.
  • With improvements to Beacon Street in Somerville as well as the access through Kendall Square, even more cyclists will crowd the bridge in the morning.
  • With the expansion of Kendall Square and its reliance—to a degree—on bus shuttles, it can not be allowed to gridlock over the bridge during peak periods (generally evening rush hour).
In other words, bikes need more room in the morning. And cars need more room in the evening (a single lane on the Longfellow would only accommodate somewhere along the lines of 50 vehicles, and might quickly queue in to Kendall). Luckily, these needs are not necessarily mutually exclusive, and a part-time bike lane would be a possible solution to give bikes the room they need at peak times, while not piling traffic in to Kendall at other times.

In general, part-time bike lanes have been created when parking is allowed at some times and not others (here's an example from the Embarcadero in San Francisco). The Longfellow is unique in that it has dramatically different usage rates between motor vehicles and bicycles (there are probably twice as many bikes in the morning than the evening, and twice as many cars in the evening than the morning). Bridge real estate is obviously limited—in a perfect world there would be two lanes for traffic and a wide, buffered bike lane, and a pedestrian promenade. So it would be a engineering, logistical and educational challenge to implement such a program.

Here's the thing: the bridge will be effectively shut down for three years. Traffic will be shifted around for long enough that drivers won't well remember the previous infrastructure, so it would be a good time (perhaps the only time) to try something drastically new. Here's a sketch of an idea:

Between Kendall Square and Memorial Drive, Main Street will merge from two lanes to one, to the left. The right lane will be for turns on to Memorial Drive only, and will be set off from straight-ahead traffic with bollards or a median.

Past the Memorial drive ramps:
The left inbound lane is kept at 11 feet and all non-Memorial traffic merges in to it before the bridge. The constriction for the Longfellow traffic is throughput at Charles Circle, so this shouldn't dramatically affect traffic, especially since Memorial Drive traffic would exit in a dedicated lane. This will allow traffic to comfortably travel in it at all times. The lane would be signed as Vehicle Traffic, All Times. It would be separated from the right lane by an unusual marking such as a double broken white line. 
The right inbound lane should be narrowed to 9 feet in width. Height restrictions (chains hanging from an overhead support) could be hung at intervals to discourage trucks and buses but signage would likely suffice. It would be signed as Bikes Only Except Weekdays 3 PM to 7 PM. No Trucks or Buses. It would be marked with diamonds or some other similar feature as well as "Sharrows" and separated from the bike lane by two solid white lines with no painted buffer in between, potentially with infrequent breaks.  
The bike lane would be 6 feet wide and the two lines would serve as a 2 foot buffer at evening peak. It would be signed as a regular bike lane.
This will extend to the top of the bridge where the grade evens. Beyond that point, there is less need for a "climbing lane" for cyclists, and the bike lane will taper to one, buffered lane. The left lane stay 11 feet, and the right lane 9, but it will be open to cars at all times, with a continued buffered bike lane. Having the right lane closed to trucks and buses will dramatically increase the comfort level for bicyclists who are often squeezed by large vehicles, who will have no business in the right lane.

At the Cambridge End of the bridge, the merge to one lane before the Memorial Drive will funnel all Cambridge-origin traffic in to the left lane (this is the only origin for trucks and buses which can not fit under the Memorial Drive bridges). During non-peak afternoon hours, the Memorial Drive intersection would then join this traffic in a short merge lane after crossing the bicycle facility. At peak hours, it would continue in the right lane. This means that for a truck or bus to use the right lane, it would have to actively change lanes, meaning that even during rush hour, bicyclists would not be pinched by frequent tall tour buses and delivery vehicles. And at other times, most of the origin traffic from Cambridge would already be in the left lane, and only the Memorial Drive traffic—which already stops at a stop sign—would have to be signed in to the lane based on the time of day. The irregular lane markings will clue most drivers in to the fact that there is something different about the bridge, as will signage placed on the bridge approaches.

At the Boston end of the bridge, just before "salt/pepper shaker" the bridge could be widened (for instance, see this older image) to allow bicyclists to stay in a buffered bike lane and cars to sort in to three full (if narrow) lanes. However, two lanes might be preferable to allow trucks and buses to get from the left lane on to Charles Street (or such vehicles could be forbidden from this maneuver and forced straight on to Cambridge or left on to Embankment Road). In this case, enough room for side-by-side cycling in a bike lane—at least 7 or 8 feet—should be allowed (this is not showin the above schematic).

The potential for a flyover bike ramp to the unused portion of Embankment Road should not be discounted, either, as it would siphon much of the bicycle traffic away from the congested Charles Circle area. I called this the "Gateway Overpass" as a lower, gentler and wider bridge could span from the Embankment Road area across Storrow Drive to the Esplanade and allow easy egress to Charles Street across the Storrow offramp. The current bridge is narrow, steep and congested, and provides far more clearance over Storrow Drive than necessary. A new bridge is proposed (see page 10 of this PDF) but I think a level bicycle facility would be very helpful to help bikes avoid the congestion at Charles Circle.

If this project were found to be either dangerous for cyclists or a major impediment to traffic in Cambridge, it could be changed simply by restriping existing lanes, so there would be no major cost involved. If it constricted traffic enough, the lanes could be restriped with a buffer to allow a wider cycling facility inbound at all times.

I think it's worth study, if not a try.

Thursday, June 13, 2013

Hubway + Umbrella: Great Life Hack, or Greatest Life Hack?

As I left a meeting today, a light rain had begun to fall. I wanted to go from Powderhouse Square to the Market Basket in Union Square and the bus there didn't come for fifteen minutes. The rain wasn't hard, so I hopped on a Hubway (which I've nerded out on before) for the two mile ride.

I had an umbrella (a fantastic Montbell ultralight—less than six ounces and it folds down to nothing) stashed in my bag on the front basket, and as I glided down towards Davis I took it out to see if it would keep me dry (or at least make me look like the world's lamest Mary Poppins). It sort of did, but got caught in the wind, so I lowered it down on to the handlebars and, miracle of miracles, it nested there perfectly. The drop handle bars and basket allow a small-to-medium sized umbrella to sit on the front of a Hubway bike and, as long as it's not too windy, keep your legs completely dry from falling rain.

Look, ma! Dry pants!
I had a helmet and rain coat, and with the umbrella and fenders my khaki-clad legs stayed dry. I find that the worst part of riding in the rain is the water shooting off the fender and soaking your legs from below as the rain dampens them from above. With this hack, I was able to cycle in a moderate ran and stay mostly dry. And my stuff stayed dry, too.

At no time did the umbrella try to blow away, and at no time did I feel like I had to tie it down to keep it dry. I biked along at a leisurely pace, and when I got to the rack near the grocery store, I snapped a picture and walked the rest of the way. Would this work in a hurricane? No. But it makes bicycling much more palatable when there's a light rain coming down. If ever I'm tempted to drive when it's raining, I now have one less excuse. Especially if Hubway comes to Dana Park (pretty please).

6000 Bikes Per Hour

A few weeks ago, a sea of cyclists pedaled (slowly) through Cambridge. The city has two annual recreational rides, complete with police escorts, where hundreds of bicyclists take to the streets. I took a video of the procession through Inman Square and it got lost in my phone for a while, but recently resurfaced and made it to Youtube.

It's not that much to watch, unless you really like watching chatty cyclists at low speed, but it is illustrative how space-efficient cyclists are. The video lasts a bit shy of three minutes, and for about 2:30 of that (give or take) the swarm of cyclists passes by. I happen to know that there were about 250 (actually 258, according to the website). But let's use round numbers—even at low speed there were 100 cyclists passing by per minute.

Which is extremely efficient.

On a freeway, a lane of traffic can only carry at most 2000 vehicles per hour—beyond that the roadway devolves quickly in to gridlock (and the number of vehicles drops). Yet one lane of bicyclists can accommodate three times as many people—you'd have to have three or four people in every car on a freeway to have the same level of service. Want to fill buses? Fine, but you better be able to get a full bus through every 30 seconds to match a lane of cyclists. Rail can surpass this capacity—at rush hour the Red Line in Cambridge peaks over 10,000 people per hour, and some lines in New York go past 20,000—but you need a bit more infrastructure to run such rail routes.

Since bicycles take up far less space than vehicles, they use road space much more efficiently than vehicles. Even if a rate of 6000 per hour necessitates a police escort, it's still a testament to the efficiency of the bicycle.

Tuesday, June 4, 2013

Longfellow Bike Traffic update

I came in this morning across the Longfellow. As I jockeyed for position through Kendall, I knew it was going to be busy on the bridge. I've seen ten bicycles per light cycle on the bridge, but today the lane was chock-a-block with bikes all the way across the bridge. With minimal auto traffic, faster cyclists were swinging in to the right lane and passing slower cyclists. And when we got to the bottom, well, it was quite a sight.

I quickly hopped the sidewalk to take a picture. By my quick count, there were 18 cyclists in line waiting for the light to change at the bottom of the bridge. Last month, I'd assumed 10 bicyclists per light cycle, which would equate to 360 per hour. At 18 bicyclists, this is an astounding 648 bicycles per hour, or one every six seconds. That's nearly as many vehicles as use the entire bridge in the AM peak (707). And this is despite the fact that the Longfellow is a narrow and bumpy bicycle facility.

So it is a shame that the current plan for the bridge allocates just as much space to vehicles, and does not appreciably expand the inbound bicycle facility. As we crossed today there were few vehicles, but bicycles could barely fit in the lane. Since the bridge hasn't been rebuilt yet, there is still time to advocate for fewer vehicle lanes (one lane expanding to two would be mostly adequate) and a much wider bike lane allowing for passing and a buffer.

The current bicycle counts are only for the evening commute where, as I've pointed out before, it's much harder to get to the Longfellow due to traffic, topography and one-way streets. I think it's high time for a peak morning bike count on the Longfellow. And time to suggest to MassDOT they reexamine the user base for the roadway before it gets reconstructed and restriped.

Plus, if we have 650 bikes per hour using the current, subpar facility, imagine the bike traffic once the lane is wider and well-paved. To infinity and beyond! Or, at least, to 1000.

Monday, June 3, 2013

Low-capital, bridge-based tidal power

This past weekend took me on a bike ride across Portland, Maine's Tukey's Bridge. Thanks to the vagaries of the bicycle network in Portland (another long post), we looped under the bridge before crossing over it.

As we did, I noticed the tide going out. Portland's back cove is not a particularly large body of water, it's about one square mile. Nor is it deep—at low tide it mostly empties in to the Atlantic and becomes a large mud flat. But all the water has to go somewhere, and it certainly does: it flows under Tukey's bridge. Portland's tides—around 10 feet—are relatively large but nowhere near those up in the Bay of Fundy. But where the water rushes in and out of the Back Cove, there is a decent current which occurs several hours each day. Every day.

The flow is increased by the current incarnation of the bridge, which is built on fill to narrow the mouth of the cove considerably. So now the square mile of water has to flow through an opening only about 250 feet wide. There's power in that water, and while it's certainly not megawatts, the infrastructure seems to be such that you could pretty easily install a small-scale tidal power system to take advantage.

Tukey's bridge has two main passages. What if, in one of them, you installed a paddle wheel contraption between the supports with a generator on one end? There is no need to worry about building supports; the bridge abutments are in place. There is no worry about navigation; small boats could easily pass through the other half of the bridge. There would have to be some sort of floating barrier to keep boaters from running through such machinery, but that would be doable. The paddles would not reach the floor of the cove, so they wouldn't interrupt whatever ground fisheries there are there. The generator could be housed on the bridge abutment out of the water, which would keep it out of corrosive salt water.

So if we assume that all the agencies (and I'm figuring NOAA, Army Core, the DOT and others would be involved) could be satisfied, would this work as a demonstration project? Could it conceivably have a payback time that would make it economically feasible? It seems like a low-cost project. All you'd need is a generator, some power lines and some concrete to anchor it to the bridge.

Or do I have the physics of it all wrong anyway?