Tag Archives: District of Columbia

Monsere, Dill et al. — Not Yet a Review, But…

M. Kary, who prepared a review of the Lusk et al Montreal study, has had a preliminary look at the Monsere, Dill et al. study of barrier-separated on-street bikeways (“cycle tracks”) which the bicycle industry lobby PeopleforBikes is promoting as demonstrating their safety. Dr. Kary has given me permission to publish his comments here.

An Introduction To and Overview Of:
Monsere C, Dill J, et al. (2014) Lessons From The Green Lanes: Evaluating Protected Bike Lanes In The U.S. Final Report, NITC-RR-583

To begin with a platitude: traffic accidents are rare events. The totals are large only because the overall volumes of exposure are huge. Therefore, if considering safety in terms of outcomes rather than the underlying mechanisms of operation, any facility, no matter how poorly designed, will appear safe if examined over a short period of time.

But collecting data over a long period of time has its disadvantages too: not just cost and delay, but also the averaging, and therefore blurring, of the effects of various changing causes and circumstances. Nor does it work at all for facilities that are yet to be built. In response to these problems, engineers developed the methods of traffic conflict analysis. They can be seen as based on the following logical and kinematic necessities. First, in order for a collision to occur, the vehicles involved must eventually get on a collision course. Second, in order to get on a collision course, they must first get on a near-collision course. On the other hand, not all vehicles once on collision or near-collision course do end up colliding: their operators make course corrections and avoid that outcome. Such potentially dangerous but often ultimately safe trajectories, i.e. traffic conflicts, occur much more frequently than actual collisions, deaths, or injuries. If there exists a suitable relationship between the former and the latter, then conflict analysis can be used to study road safety at reduced cost, with better timing, and even via simulation modelling of facilities that have been designed but not yet built.

The theory and practice of conflict analysis for motor vehicles has been developed over something like a half a century of research. This has evolved to quantitative methods using not just traffic cameras, but also instrumented vehicles, automated data extraction, and theoretical concepts such as time to collision, gap time, gap acceptance, post-encroachment time, and many others. There is no such corresponding body of research for bicycles. Even if there were, it could never be as important to bicycle or pedestrian deaths and injuries as it is for the occupants of cars and trucks: for example, the latter vehicles never topple over at stops or just slip and fall, so that their occupants fracture an arm or strike their heads on a curb. In fact the majority of bicyclist injuries, even those requiring hospitalization, apparently involve only the bicyclist, making conflict analysis entirely or at least largely irrelevant to them.

On the other hand collisions with motor vehicles are major factors in cyclist deaths and injuries, and they are what cyclists worry most about. And even apparently bicycle-only crashes can be provoked by e.g. general fears or specific intimidations, or avoidance manoeuvres leading to loss of control. Thus there are also dimensions of traffic conflicts applicable to bicycling, but either inapplicable or less so to motor vehicle-only conflicts. Nor is every conflict visible or strictly kinematic: consider for example the effects of sudden and loud horn honking or engine revving.

With these fundamental limitations in mind, obviously traffic conflict analysis is a promising method for investigating important aspects of bicycling safety. The theory needs to be developed, so we can figure out what constitutes a high or low rate of conflicts, what types of conflicts figure what way into which accident types, and how vehicle operators and pedestrians cope with them, such as through hypervigilance, or avoidance of the area and thus diversion of problems to a different one.

Not only does the theory need to be developed, but also the methods of data extraction and analysis: the subjective review of traffic camera recordings, typically of low quality, is a mind-numbingly tedious, labour-intensive and error-prone task, that does not scale well.

The work of Monsere et al. (2014), Lessons From The Green Lanes: Evaluating Protected Bike Lanes In The U.S., should be considered a pilot project in this effort, although the authors themselves do not describe it as such.

Monsere et al. aimed to address six questions:

  1. Do the facilities attract more cyclists?
  2. How well do the design features of the facilities work? In particular, do both the users of the protected bicycle facility and adjacent travel lanes understand the design intents of the facility, especially unique or experimental treatments at intersections?
  3. Do the protected lanes improve users’ perceptions of safety?
  4. What are the perceptions of nearby residents?
  5. How attractive are the protected lanes to different groups of people?
  6. Is the installation of the lanes associated with measureable increases in economic activity?

Apart from noting that, as with most sociological research, their survey response rates were dismally low (23-33% overall, counting even only partially completed surveys as full responses), to produce a socioeconomically skewed sample (e.g. the bicyclists being 89% white, 68% male, 82% having at least a four-year college degree, and 48% with annual incomes over $100,000)— this overview of their work considers only the first part of their question No. 2.

Monsere et al. installed video cameras along short bicycle sidepaths (“protected lanes”, “cycle tracks”) constructed between approximately the summer of 2012 and the early summer of 2013 as part of the Green Lanes Project. These were in four U.S. cities, San Francisco (two 0.3 mile paths), Portland (one 0.8 mile path), Chicago (0.8 and 1.2 mile paths) and Washington (a 1.12 mile path; no cameras were installed in Austin, although sociological surveys were conducted there). They did their video recording chiefly at intersections, six in these four cities in the summer and fall of 2013. This was then presumably while the users were still in a cautious or exploratory state, as they got used to the new facilities.

Only 12-18, or in one case 20, independent hours of video were analyzed from each intersection. As each intersection examined was given a unique treatment, results cannot easily be pooled. These are very small numbers.

(This makes for substantially less than 120 hours total. The authors seem to say they analyzed 144 hours of video at intersections. This would mean that some of this total came from multiple cameras examining the same intersection at the same time. The authors do show frame captures from some of their cameras. This observer would find it difficult to correctly identify the conflicts from the views on display.)

As noted following the opening platitude, any facility, no matter how poorly designed, will appear safe if examined over a short enough period of time.

The six facilities examined were all so new (less than or little more than a calendar year old) that there were no injury or death data available for them. (For comparison, the entire city and island of Montreal, with all its thousands of intersections, averages of late about five cyclist deaths and 25-50 police-recorded serious cycling injuries per year.) Thus, there would not have been a way to use even many more hours of recording to examine for any relationship between the surrogate outcomes (conflicts, violations or errant behaviours) and the outcomes of most interest, deaths and injuries.

Further, as this was neither a before-after study nor a comparison with standard intersections, there is no way to know whether the numbers of observed conflicts, violations, or errant behaviours, were themselves high or low.

As to the actual results from this pilot project, the much touted headline was that there were only six minor conflicts found, out of nearly 12,900 bicycle movements through intersections. The most basic problems with this headline are:

1. It is the wrong comparison. The conflict rate has to be the number of conflicts divided by the number of occasions where at least two users capable of conflicting are present, e.g. a bicycle and at least one other bicycle, pedestrian, or motor vehicle. Thus the authors give figures of 7574 turning motor vehicles, but only 1997 turning motor vehicles with bicycles present. The corresponding conflict rates (which they normalize by the products of bicycle and motor vehicle movements, not by the numbers of bicycle movements alone) they give for the individual intersections therefore vary by factors of approximately 3 to 10, depending on which figures are used.

2. Six is the total of observed “minor” conflicts, not the total number of observed conflicts. There were also 379 “precautionary” conflicts with motor vehicles, 216 with pedestrians, and 70 with other bicycles.

3. Besides conflicts, there were numerous violations or other errant behaviours: e.g. 9-70% of bicycles and 7-52% of turning motor vehicles in the various intersection designs used the lanes incorrectly, 1-18% of turning motor vehicles in the various mixing zone designs turned from the wrong lane, 5-10% of motorists turned illegally on red arrows at intersections with bicycle-specific signals, and 7-23% of bicyclists disobeyed their signals.

4. Without any theory or model of how any of these occurrences or their frequencies relate to death, injury, or property damage, and without any before-after or non-sidepath comparison data— not to mention, with the very small numbers of observation hours— there are almost no safety implications, positive or negative. The only concrete result is that one of the local authorities apparently deemed the problem of motor vehicles turning from the wrong lane (18%), straddling lanes (another 17%), or entering the turn lane early (15%) to be so severe that they later removed the intersection treatment and replaced it with another design (at Fell and Baker in San Francisco).

5. The sociological surveys tell another story: one-third of all bicyclists surveyed said they had been involved in at least one near collision on the paths, while 2% experienced an actual collision. 23% had a near collision with turning cars, 1.8% an actual collision with turning cars; 19% a near collision with a pedestrian, and 0.4% an actual collision with a pedestrian.

In short: this is an interesting pilot project, whose methods are impractical for the amount of data collection needed for meaningful safety results. Even with better methods, conflicts are only one facet of the bicycling, and overall safety picture; while road designers and road users, whether bicyclists or motorists, have to consider more than just safety. Convenience, transit time, cost, and greenhouse gas emissions also matter. A cycle track that, like the downtown de Maisonneuve track in Montreal, lies largely dormant in the winter, but delays motor vehicle traffic in the winter and ties it up spring, summer and fall, will be of no help in reducing CO2 emissions. The much touted headline results from this study are selective, overblown, and misleading. Any facility will appear safe if examined over a short enough period of time, and surely 12 to 20 hours each is short enough

Ian Cooper comments on the C&O Towpath

Cyclist Ian Cooper offers a report on the C&O canal towpath, which I have mentioned in a previous post. Supreme Court Justice William O. Douglas deserves a lot of credit for preserving the canal as a park, but as Ian reports, it does not make the grade as a bicycle facility.

Ian Cooper with Trail-a-Bike rig on the C&O towpath trail

Ian Cooper with Trail-a-Bike rig on the C&O towpath trail

Aside from the issues of safety and of priorities which Ian raises, do the parts of the path which are “paved” with pebbles the size of golf balls meet the National Park Service’s criteria to prohibit cyclists from parallel roads, introduced into the current transportation bill in Congress?

An article in the Pittsburgh Tribune-Review newspaper seconds some of Ian’s comments, while indicating that improvements are in the works. The effectiveness of the improvements is certainly open to question: more gravel will not eliminate dropoffs or necessarily provide a good or durable riding surface. The article includes the photo below.

Rough conditions on the C&O towpath trail

Rough conditions on the C&O towpath trail, Paul Christensen photo for the Tribune-Review

An online article by a bicycle tourist also reports some difficult conditions on the trail.

Ian says about that article:

The first image on the left of the page shows a little of how muddy it can get, though it can be worse than this when the path gets very narrow and bumpy. This is a different area of the trail (farther north than my ride), and again this is very wide and non-grassy in comparison with some of the trail south of Harper’s Ferry and Point of Rocks, MD. The author tells how safety is a real issue on the trail due to the bad condition of the surface.

In both the above images, the wide trail allows you to choose a path through the mud. This isn’t always the case in the part my daughter and I cycled. Sometimes you just have to stop and walk. Sometimes you get no warning, hit a pothole or a mud patch and have to rely on skill to maintain control.

Here are Ian’s comments on his own ride:

I know the C&O well. Here on the Maryland side it’s not paved, and I think anyone doing more than 10 mph on it would be taking a grave risk. I cycled with my daughter from DC to Harper’s Ferry June 2nd – 3rd, 2011 with my daughter on a Trail-a-Bike behind me. I will never use it again, as the National Park Service has stated that it must remain unpaved, as it is to retain its historical attributes as a canal towpath. The only reason I didn’t give up on using it during that trip is that I have a lot of experience cycling in winter conditions, so I had confidence that I could counter-steer and retain balance during times when the bike lost traction in the mud. Also, we were heading north, so we were cycling on the canal side of the trail, where the drop-off was only 10ft. I dread to think what might happen if a less confident or less skilled cyclist lost control going southward and fell into the river.

We averaged 5mph. On regular roads, I would have done the trip in less than half the time (in part because the road goes pretty much straight there, while the ‘so-called’ multi-use trail takes a dog-leg approach alongside the river). Also, this trail is overgrown with weeds, is ‘paved’ with loose pebbles the size of golf balls, and is 4 ft wide in places with mud patches and 10+ft drops on each side. In my view it is the worst bike trail I’ve ever seen and is literally a death trap for cyclists (which is presumably why bike trail advocates avoid referring to it as a bike trail). Sadly, most so-called bike infrastructure is poorly designed, poorly implemented and lacking in funding for maintenance. I have yet to see a bike trail or bike path that is well designed, well implemented and well maintained. Until I do see such a thing, I am 100% against such follies.

The photo below was taken around 12 noon on June 3 somewhere near White’s Ferry and is the only image I have showing the actual trail. It shows what should be considered a ‘good’ part of the trail in this area – this part is wide, relatively flat and has only a gentle slope away to the canal on one side. As you can see, even though there’s perhaps 8ft of trail, most of it is grassed over and there’s only two thin tracks of usable surface. Sometimes the trail gets so treacherous that the wet and slippery grass in the middle becomes the safest place to ride.

A better section of the C&O towpath trail

A better section of the C&O towpath trail

The C&O has few road crossings, it’s true. But if you use it in May or June, before the flood season is completely over (and presumably before any yearly maintenance is carried out before the summer season), you see it at its worst, when it is difficult just to maintain control of the bike. At some points, especially the stretch between Seneca and Point of Rocks, MD, it is quite literally frightening. In many places the trail is very narrow, it has a steep ten foot drop on one side to the old canal, and a steep twenty foot or more drop on the other side to the river (sometimes both at the same time). In May and June, the trail is so overgrown that stinging nettle bushes often thrust out into the trail. The trail is filled with pebbles and rocks, and overgrown grass and stinging nettles sometimes make all but a section between 6 and 12 inches wide unusable. This thin section can be muddy, it can change from dry to wet very quickly, it can be deeply rutted from use by previous cyclists, and other parts can be washed out so badly that cyclists can experience sudden potholes. It is extremely treacherous.

In my view, this stretch of the C&O Canal towpath should be closed as a multi-use path as its lack of adequate maintenance means that it is only a matter of time before a cyclist or a runner gets killed on it.

The Six-Way in Rush Hour

Here’s another video showing conditions at the six-way intersection of 16th Street, U Street and New Hampshire Avenue NW in Washington, DC, where special bicycle facilities have been installed.

Also please see my earlier post about this intersection, with another embedded video.

About Supreme Court Justice William O. Douglas, bikeways, class issues and segregation

The 184.5 mile long Chesapeake & Ohio Canal Historic Park is located along the north bank of the Potomac River, between Washington, DC and Cumberland, Maryland.

I recently had the occasion to see the park described in writing as a “class I bikeway”.

So, what is that? A high-class bikeway? Read on.

The California Department of Transportation used this nondescriptive and somewhat judgmental term in its 1970s manual. The “I” in “Class I”, is pronounced as a Roman numeral rather than letter “I”, as becomes clearer when “Class I” is seen alongside “Class II” — bike lane — and “Class III” — designated route on shared roadway, which, thank goodness, is not pronounced “Class aye aye aye” :-). When the California manual became the basis for the first AASHTO bicycle facilities guide in 1980-1981, the term “Class I” was replaced by “bicycle path” — and later, “multi-use path”, corresponding to the actual traffic mix observed.

A few years ago, I rode part of the C&O (only had part of one day to do it) near the Antietam battlefield and found it to be an unimproved, muddy canal towpath, — though certainly scenic and historic. As of a couple of years ago, the stretch nearest Washington, DC has a crushed stone surface, but the rest still has a dirt surface. Hike/biker campgrounds and porta-potties are available every few miles, though.

That this corridor was preserved as a linear park and not converted into a limited-access highway is due in large part to the efforts of former Supreme Court Justice William O. Douglas (judicial activism, but while walking, rather than sitting on the bench..!?), see this report.

Keep reading after the part about the towpath, and you will see that the report also describes a very historic event, the issuance of the Supreme Court’s ruling in Brown vs. Board of Education.

The ruling was unanimous. The Justices read the Constitution as opposing segregation, but we’re not talking about segregated bicycle facilities here. Little controversy over them had arisen yet in 1954.

I approve of this?

UPDATE: This post gives background information on the intersection. I have now ridden through it, and my opinion of it has changed. I have another post about it, and a video. Please check them out.


The image below shows a special installation of traffic signals and markings at the intersection of 16th street, U Street and New Hampshire Avenue NW in Washington, DC. To enlarge the image so you can read the text descriptions, click on it. You also may have a look at a Google map satellite view. Then please return to this page for my comments.

16th Street, U Street and New Hampshire Avenue NW, Washington, DC

16th Street, U Street and New Hampshire Avenue NW, Washington, DC

Pierre L’Enfant and Andrew Ellicott — and let’s also not forget African-American surveyor Benjamin Banneker — laid out Washington’s streets from scratch –  in the pre-automotive 1790s. Washington’s diagonal avenues give it an openness and unique sense of place — but the resulting uneven-length blocks and multi-way intersections make for some serious headaches now. Some traffic movements are odd, traffic signals can not be synchronized efficiently…

Before the new installation, no signals in this intersection faced new Hampshire Avenue. Bicyclists would sometimes use New Hampshire Avenue for through travel, though its conflicting one-way segments made that illegal and there was no conflict-free crossing interval.

The illustration above is from a page posted by the government of the District of Columbia describing a new installation of contraflow bicycle lanes, bicycle waiting boxes and special traffic signals. At first glance, these may raise the hair on the back of the necks of people who are suspicious of special bicycle facilities treatments.

Look again. The bike boxes look odd only because they connect with diagonal New Hampshire Avenue. They are cross-street bike boxes — which bicyclists enter from the left. Bicyclists from New Hampshire Avenue enter on a separate signal phase from the motor traffic on 16th Street, rather than to creep up on the right side of motor vehicles, as with more-usual bike-box installations. Motorists do not have to crane their necks or stare into a right-side mirror looking for these bicyclists.

The cross-street bike boxes are even more conflict-free than usual. Because only bicycle traffic runs contraflow, bicyclists do not have to negotiate with any right-turning traffic when entering the intersection.

To summarize: this installation, importantly, does not violate the fundamental traffic-engineering principle of destination positioning at intersections, as so many special bicycle facilities installations do.

Or, looking at the same conclusion from a different point of view, the installation does not require or encourage bicyclists to do anything dangerous or stupid, and it offers reasonable travel efficiency considering the situation it addresses.

I am not going to say that this installation is perfect. I can see the following issues.

  • Bicyclists’ having to wait through two traffic-signal phases is inconvenient and might lead to scofflaw behavior. A “scramble phase” could allow crossing in one step and might even apply to bicyclists arriving from other directions. It would reduce the time allocated to for all the other phases, but it might be practical, and preferable, at times of low traffic. Signals and markings which only apply at some times could, however, be confusing.
  • The installation addresses only bicycle traffic entering the intersection from New Hampshire Avenue. Traffic control remains as it was for 16th street and U street. Considering the many ways in which bicycle travel could be made slower and/or more hazardous in the name of making it better, this may be a case of “best leave well enough alone,”  but on the other hand, real improvements might be possible.
  • The bike boxes on 16th street could be interpreted as encouraging bicyclists on that street to overtake motorists on the right, then swerve in front of them, as is the more conventional with bike boxes.
  • Just outside the lower left of the picture on New Hampshire Avenue, there is wrong-way parallel parking next to the bike lane. Motorists exiting wrong-way parking spaces are in head-on conflict with bicyclists, but cannot see them if another vehicle is parked ahead. (See illustrated description of wrong-way parallel parking elsewhere, if the explanation here is unclear.) At the top right, on the other hand, note that the bike lane is farther from the curb: this segment of New Hampshire Avenue has back-in right-angle parking, avoiding the sight-line problem.
  • And, while we’re at it, I have another issue with the street grid, though it’s common to many other cities and not readily subject to correction. Streets that go east and west guarantee that twice per year,  for several days, the Sun will rise and set directly along the streets, glaring into drivers’ eyes.  If the street grid ran northeast to southwest and northwest to southeast, this would never happen. All you Pierre L’Enfants of today designing new cities, please take notice, here’s your chance to acquire a reputation as Pierre L’Enfant Terrible!

This installation is the subject of experimentation sanctioned by the U.S. Federal Highway Administration, with observation, data recording and analysis to see how it works in practice. The experimentation may turn up more issues, or reveal that some are of little importance.

Now, dear readers, you also may also have points to add to the discussion. Let the comments fly.

See also: GreaterGreaterWashington blog entry about this installation; Washington, DC Department of Transportation page about it; Google maps satellite view.