Commonwealth Avenue Improvement Project

[North Shore]

North Shore, welcome. PLEASE stick around even if we debate with you. A lot of us here are either well versed in the critique process, or simply like to argue in general. Your knowledge however will be invaluable, especially as this forum has taken a distinct urban planning turn as of late.

Again, welcome and thanks for the input.

Oh, I'm not going anywhere. I would have been here sooner (commenting on the Beacon Hill wheelchair ramps thread - another one of my specialties), but I just didn't have the time to post.

 

[Matthew]

As one of "those engineers" that you seemingly have disdain for, we are required, as professionals, to utilize Federal Standards (and their local amendments) along with AASHTO standards to design infrastructure with regard to roadways with pedestrian and/or bicycle accommodation.

I don't disdain you so please don't take it personally. I'm just very well versed on cynicism towards traffic engineering, and I think you would agree that it's for a very good reason.

I know I'm gonna regret stating this, but it is simply asinine to design improvements for a heavily trafficked corridor such as Comm ave. with pedestrians as the primary influence. For starters, there's no guideline in place to do so.

Several things: the design of Comm Ave comes from the City of Boston, which has the Boston Complete Streets guidelines, not to mention NACTO, to work with. Second, designing city streets with pedestrians as the primary influence is precisely what should be happening everywhere that it makes sense. I'm not sure if you're aware of this, but: pedestrians and transit users completely dominate Comm Ave usage numbers. Failing to design first for pedestrians would be tantamount to ignoring the biggest, most vulnerable group of street users.

You have to start with something and frankly, there's systems in place for the use of vehicular data as the primary design for roadways with pedestrian accommodation. No designer in their right mind would ever design with pedestrians as the primary source. There's just simply too many variables involved. What's the limiting factor at play here? Vehicles. They are the most dangerous aspect at play, along with the geometry.

The point of these reforms is to establish systems that are different from the old ways. Perhaps in the old days they only counted vehicles and all decisions were made with vehicles in mind. Pedestrians were given whatever scraps of space and time that were left over. I hope that you would agree about that not being the proper way to go about things these days and I hope that in the future it won't be so contentious to design primarily around pedestrians in a city.

Yes, we use LOS as one means to help us figure out cycle lengths. But pedestrian accommodation will be the same regardless if an intersection is a LOS A or a LOS F. You can't let pedestrians walk into a street and have the light change on them. It just simply doesn't happen. We can change green times for approaches and turn movements, but the ped. phasing is what it is.

Choice of pedestrian phasing alternatives can most certainly affect the Level Of Service of an intersection. I am aware of several cases where engineers are considering the conversion of an exclusive pedestrian phase to a concurrent pedestrian phase precisely because such a change would increase the LOS of the intersection.

I would also contend that "it simply doesn't happen" is not true. I'm aware that the rules and regulations should make it impossible for pedestrians to get caught in an intersection, but they are not always followed properly in the real world. Sometimes procedures fail, for whatever reason. As I mentioned earlier, I know of intersections that are timed for walking speeds as high as 5 f/s, which is far beyond most people's capabilities.

In general, I don't think LOS is an appropriate metric for city streets. It only focuses on one aspect: the delay experienced by automobile drivers, to the exclusion of all other users of the street. LOS is a metric that was originally created to rate limited access highways, and the usage of it to rate city streets/intersections has been an unmitigated disaster for cities. City streets need to fulfill many different roles, of which carrying vehicular traffic is only one, and in many cases, not the most important role.

 

[The EGE]

Anecdotally, I cross the St. Mary's Street intersection at least once today. Today it was four times. Not once this week have I crossed fully on a pedestrian signal; only three half-crossings were even on pedestrian signals. The three intersections to the west can be plausibly crossed in a single light cycle, but St. Mary's cannot.

They did retime the light sometime over the summer. It used to be that the westbound traffic got the green exactly as the pedestrian timeout hit zero; now there's about a 3-second lag.

 

[ErnieAdams]

^Similar issues at Pleasant St., though granted it's beyond the realm of the earlier phase's improvements. Not a chance of making it across this one in one gasp from the north side. From the south side you actually stand a chance, but only if you jaywalk it with the knowledge that the WB cars are stuck at a red, waiting for left turns out from Pleasant. The ped signal was not programmed with this in mind, and everyone there has an awkward red for about 15 seconds.

This is the primary crossing for anyone who parked in, or came from, North Brookline to go to an event at Agganis. Certainly not ideal to have dozens of people leaving an event and standing in the 8-foot clearance (if that) between the EB B-line and the EB cars, but here we are.

 

[ant8904]

It's a short caption to a photo. It's supposed to be snappy. I'm not going to resort to John Kerry-esque statements in a caption.

Why did you rewrote my username to my real name? We have met in real life, but you met others too and you maintain their alias afaik.

 

[Matthew]

I think it's because I can never remember the collection of numbers you have after "ant" and I had completely mangled the quote mechanism thingy when I posted that reply.

 

[Justin7]

North Shore, welcome. PLEASE stick around even if we debate with you. A lot of us here are either well versed in the critique process, or simply like to argue in general. Your knowledge however will be invaluable, especially as this forum has taken a distinct urban planning turn as of late.

Again, welcome and thanks for the input.

This is far more reasoned and diplomatic than my intended "Go back to the hell that spawned you!" post.

Joking, but I do wonder how one finds it reasonable to have 15 pedestrians made to stand and wait for two walk signals (one while standing in the median) rather than lower the convenience of likely fewer people sitting in cars at a red light.

 

[millerm277]

Joking, but I do wonder how one finds it reasonable to have 15 pedestrians made to stand and wait for two walk signals (one while standing in the median) rather than lower the convenience of likely fewer people sitting in cars at a red light.

The delay to an individual pedestrian in each trip from having the lights like this is not much, they only cross Comm Ave once, regardless of if they're going a long distance down Comm Ave or not. (Unless they're lost, I suppose).

In contrast, if you applied this logic along Comm Ave, the change in trip time for the car would be large, as the car goes through many lights.

 

[Matthew]

The delay to an individual pedestrian in each trip from having the lights like this is not much, they only cross Comm Ave once, regardless of if they're going a long distance down Comm Ave or not. (Unless they're lost, I suppose).

In contrast, if you applied this logic along Comm Ave, the change in trip time for the car would be large, as the car goes through many lights.

This isn't really an argument made for car vs pedestrian but rather for travel along Comm Ave vs across. And it does make some sense that there's more people traveling along Comm Ave (mostly on sidewalks and on the Green Line) than across. But there are also a lot of people crossing Comm Ave, clearly more than the current signal timing can handle. Especially in between classes, where it overflows. The current wait time is plainly too long.

Now, I tend to favor shorter cycles in general. It's true that shorter cycles are less efficient for traffic flow. However, shorter cycles are also less frustrating (for all users) because you always know that you will be able to proceed shortly even if you get caught at the worst moment. I think that trading off pure efficiency for predictability and less frustration is well worth doing, particularly in a city environment with heavy pedestrian usage, and where pure vehicular efficiency is simply not as important as providing a good walking environment. That's why San Francisco applies the policy widely, for instance.

Also, proper signal coordination can alleviate some of the stop-and-go concerns. I know we're accustomed to terrible coordination, so we assume that having traffic lights will always suck, but that's simply not necessary.

 

[Matthew]

A relevant article for Comm Ave, and required reading for all traffic engineers, everywhere:

http://www.citylab.com/design/2014/...s-for-safety-and-must-be-replaced-now/381117/

[States and counties] believe that wider lanes are safer. And in this belief, they are dead wrong. Or, to be more accurate, they are wrong, and thousands of Americans are dead.

Comm Ave is planned to have 11 foot lanes, it currently has 10 foot lanes. Reducing those plans back to 10 foot lanes is paramount.

 

[vanshnookenraggen]

BU Skybridge. Problem solved; next.

 

[davem]

Relevant:

...states and counties almost always apply a 12-foot standard.

Why do they do this? Because they believe that wider lanes are safer. And in this belief, they are dead wrong. Or, to be more accurate, they are wrong, and thousands of Americans are dead.

They are wrong because of a fundamental error that underlies the practice of traffic engineering—and many other disciplines—an outright refusal to acknowledge that human behavior is impacted by its environment.

 

[vanshnookenraggen]

You're an hour late on that davem.

 

[metasyntactic]

I think that trading off pure efficiency for predictability and less frustration is well worth doing, particularly in a city environment with heavy pedestrian usage, and where pure vehicular efficiency is simply not as important as providing a good walking environment.

An interesting solution to predictability I saw in Tokyo was adding countdown timers for both green and red walk signals for pedestrians (that are always active), so that it was obvious how long was left to walk and how long the cars had before you could walk again. This made the intersections somewhat tolerable despite the long cycles. Of course they also tend to have elevated walkways all over too.

 

[Justin7]

The delay to an individual pedestrian in each trip from having the lights like this is not much, they only cross Comm Ave once, regardless of if they're going a long distance down Comm Ave or not. (Unless they're lost, I suppose).

In contrast, if you applied this logic along Comm Ave, the change in trip time for the car would be large, as the car goes through many lights.

I don't suggest applying this logic all along Comm Ave. Just areas with heavy pedestrian crossings. I'm really only talking about BU, and really, I'm surprised the school hasn't done more lobbying on the issue.

 

[North Shore]

That 12 foot lane width article is dead wrong. You have to consider the context for such lanes. And that article shows no consideration for an urban location such as Boston. We always design to the book, but there's a reason there are ranges presented lane widths - you need to leave leeway so you can design into the proper context of the usage.

The AASHTO Highway Design Manual (the Green Book) and, in turn, the MassDOT Project Design & Development Guide (PDDG) specify the design widths for roadways based on their functional classification.

The only type of roadway where a 12' width is mandated is a freeway.

Comm Ave. is classified as a "Urban Other Principal Arterial". In laymen's terms, it is a major, multi-lane route with a very high ADT in a urban setting. In accordance with Exhibit 5-14 of the PDDG, the lanes should ideally be 11-12 in width, though a design waiver may be requested for 10' lanes, in accordance with the following:

"Lanes Narrower than 11-Feet
Narrower lanes reduce the amount of right-of-way dedicated to motor vehicle travel, leaving room for wider sidewalks, bicycle lanes, shoulders and on-street parking. Narrower lanes also reduce the crossing distance for pedestrians and can encourage lower operating speeds. In some settings, narrower lanes help to reduce the impact to roadside environmental or cultural resources. For lower speed, lower volume roads that primarily provide access to adjoining property, (such as minor collectors and local roads) narrower lanes may be appropriate to minimize right-of-way requirements and potential impacts to the built and natural environment.

In areas of limited right-of-way, 10-foot lanes can be provided so that the width of the shoulder can be increased to provide greater separation between pedestrians and bicycles and motor vehicles."

Because of the characteristics of Comm Ave., with a large number of trucks using the corridor, the chance of 10' lanes ever being approved is highly doubtful.

 

[North Shore]

I don't suggest applying this logic all along Comm Ave. Just areas with heavy pedestrian crossings. I'm really only talking about BU, and really, I'm surprised the school hasn't done more lobbying on the issue.

But you have to figure in the fact that Comm Ave is a coordinated corridor with the traffic signals interconnected and designed to ensure efficient traffic flow from one end to the other, including intersections with side streets.

 

[Shepard]

I don't want to offend you or your profession by saying this. And in fact I am probably mistaken so please set me straight where I'm wrong:

To me, your logic is internally valid within the narrow confines of your rules and regulations. By beyond that it's a tautology. "We must do it this way because those are the regulations / Those are the regulations because we must do it that way."

Underpinning those regulations is clearly a goal of traffic throughput. But what if that isn't the goal? What if the regulations are based on assumptions that are invalid in an urban context? Then the logic would seem to fall apart.

 

[North Shore]

I don't want to offend you or your profession by saying this. And in fact I am probably mistaken so please set me straight where I'm wrong:

To me, your logic is internally valid within the narrow confines of your rules and regulations. By beyond that it's a tautology. "We must do it this way because those are the regulations / Those are the regulations because we must do it that way."

Underpinning those regulations is clearly a goal of traffic throughput. But what if that isn't the goal? What if the regulations are based on assumptions that are invalid in an urban context? Then the logic would seem to fall apart.

First and foremost is liability. Any professional engineer who puts their stamp on a set of plans does so knowing that they have approved a design that meets established standards, practices, principals and regulations. Failure to do so opens oneself up to a plethora of litigation in the event something fails or there are faults in the design. Many an engineer have been successfully sued because they've skirted design standards (i.e. insufficient stopping sight distance at an intersection).

Second, there are mechanisms in place to adapt design standards to a variety of locations. That's why you see ranges of numbers for items such as lane width, approach angles and superelevation rates. You just need to know what limits you have in place and rearrange the variables to create a design that works best.

Long story short, you have to design in accordance with standards. Keep in mind, there are a number of publications such as AASHTO's Roadside Design Guide and ITE parking guides that are used in conjunction with the Green Book that offer supplemental design guidance. But ultimately, these publications all work with one another to help us design an number of infrastructure improvements.

 

[Matthew]

Comm Ave already has 10' lanes.

The liability issue is bunk. If that were true, then we would sue engineers for building high speed roadways in our cities that directly result in people getting killed.

I'll be less charitable than Shepard. We know very well about the traffic engineering religion around here. You're not going to dazzle us by citing AASHTO or ITE. That's why I have no compunction about challenging you on this. We know that there is no scientific basis for many of the so-called axioms of the traffic engineering field. In fact, there's quite a bit of evidence marshaled against your regulations, evidence that Jeff Speck presented, but you seem to have ignored in your zeal to make a point.

That's why people like me are challenging traffic engineers. You create these rules and regulations that you claim make things safer, but are unsafe in fact. Motorists get to go fast, pedestrians and bicyclists pay the price in blood. Enough's enough.