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Comments on Paul Smith report

John S. Allen, May 2002

MIT is proposing  to build an expensive facility which will increase crash rates for bicyclists and pedestrians alike, will be difficult and expensive to maintain, will make bicycle travel more inconvenient and slower, and will expose the Institute to a very serious liability risk. The MIT Department of Facilities hired a consultant, Paul Smith, to defend this action. The consultant produced a report in May, 2002, which does not answer questions which have been raised about the facility.

The spectrum of opinion about sidewalk bikeways

Let me begin with quotes from two prominent figures in the world of bicycling. Andy Clarke generally favors separate bikeways and bike lanes with the goal of encouraging bicycle use; John Forester criticizes their deficiencies and teaches how to ride on ordinary streets. Clarke and Forester nonetheless have the same opinion of sidewalk bikeways:

"In the 1970's...a lot of bad bikepaths were being provided by governments who didn't know better. Often they were no more than striped sidewalks. Now we do know better - and AASHTO specifically discourages the provision of sidewalk-type bikepaths. They do not discourage well-designed trails in their own rights-of-way."

Andy Clarke, formerly with the
Bicycle Federation of America,
later Executive Director of the
Rails to Trails Conservancy; now
with the Association of Bicycle
and Pedestrian Professionals  and
the Federal Highway Administration;
in a letter to Bicycle  Retailer and
Industry News
, 1994.


"Stay out of each of the following bikeway situations: bike lanes that curve right at intersections; bike lanes that require you to ride on the left side of the road; bike lanes that have berms of traffic bumps that squeeze right before intersections; bike lanes with berms, curbs or parked cars between them and the motor traffic lanes, and bike paths alongside the road like sidewalks. Every one of these situations is more dangerous than riding on the roadway because:

1. You are trapped in a narrow channel where you cannot maneuver properly to escape collisions from the cars that cross or turn across it:

2. both you and the motorists are forced to maneuver dangerously into intersections:

3. It is much harder to observe the motorist who may hit you, and much harder for the motorist to see you.

How you stay away from these situations is immaterial compared to the value of your life."

John Forester, past President,
League of American Bicyclists,
in his book Effective Cycling,
published by MIT Press.

These statements by Clarke and Forester are supported by accident studies and borne out by experience. Clarke and Forester, different as their opinions on bikeways are, agree about sidewalk bikeways.

Specific comments on Smith's report

In what follows, I have indented Smith's text to differentiate it from my comments.

Vassar Streetscape Project
Bicycle Facility Design

Paul B. Smith, AICP

AICP is the American Institute of City Planners. Mr. Smith's credentials are as a city planner. He is not trained in traffic engineering. He cites only planning literature. He does not once cite the literature of bicycle crash causation and prevention.

May 2002


This paper describes the bicycle facilities included as part of the Vassar Streetscape design project.

The design includes separate-lying one-way cycle tracks transitioning to one-way bicycle lanes at intersections.

In other words, not one single thing about the project has been changed as a result of previous comments.

The cycle tracks and bicycle lanes are designed for the exclusive use of bicycles and will be so designated by signing and pavement markings.

This is fantasy. In reality, the cycle track and the adjacent walkway will be used indiscriminately by bicyclists, inline skaters and pedestrians. Two-direction pedestrian traffic is very heavy on the Vassar street sidewalks at class break times, and a five-foot or even eight-foot walkway is inadequate to accommodate it without spillover into the adjacent bikeway. The five foot bikeway is inadequate for one bicyclist to overtake another, especially given that slower bicyclists will tend to keep away from the walkway, and faster bicyclists will then overtake by merging onto the walkway. Bicycle-bicycle and bicycle-pedestrian collisions will result, and they are often serious.

The one-way cycle track design is based on design guidelines published by the Centre for Research Standardization in Civil Engineering - The Netherlands (CROW) and the Road Directorate of Denmark.'

The Dutch and Danish practice of accommodating bicycles on sidepaths dates to before the Second World War and reflects the weight of entrenched practice and bureaucratic resistance to change -- particularly strongly because an admission of error would reveal the bureaucracy as having been responsible for avoidable injuries and fatalities. Dutch and Danish practice also is perpetuated by widespread misconceptions about bicycle crash types and causation.

Sidepath installation began without any research basis to establish whether it provided an acceptable level of safety, and has more recently been subjected to withering scrutiny through a number of European and North American research studies. These have conclusively shown that sidepaths are far more hazardous than either on-street bicycle accommodation or paths away from roads. There are no studies that show opposite results.

Choosing Denmark and the Netherlands as examples is very selective as these are the two countries where sidepath facilities are most entrenched. The story is different elsewhere in Europe. Germany, in particular, has moved decidedly away from sidepath treatments, modifying its traffic laws to remove the mandatory use of many sidepaths, and changing design guidelines to favor on-road improvements. Furthermore, and very much to the point here, Dutch and Danish guidelines are unsanctioned and unapproved in the USA.

I have provided on-line access to many European and American sidepath research studies through a Web page which I made known to the project proponents in early March, 2002. Mr. Smith does not attempt to challenge these studies; he simply ignores them. If Mr. Smith can find any studies to refute the ones I have cited, let him produce them.

The design also conforms to design guidance published by the American Association of State Highway and Transportation Officials (AASHTO)]

This statement is untrue in may ways. You may check this out for yourself: the 1999 edition of the AASHTO Guide is available from the AASHTO bookstore online, either in print, or on CD-ROM.

As the AASHTO Guide is not available on-line, I posted relevant excerpts on the Web page which I made known to the project proponents in early March. I will address specific deviations from AASHTO guidelines as I make my way through Mr. Smith's claims.

The bicycle lane design as proposed at the Massachusetts Avenue and Main Street intersections conforms to AASHTO design guidelines as well as European design guidelines.

Here's Smith's first specific misstatement about AASHTO. Bike lanes to the right of right turn lanes at major street intersections are contrary to specific AASHTO guidelines. Such bike lanes direct motorists and bicyclists alike to operate contrary to the traffic law (MGL Ch. 90 14) -- by directing motorists  to turn right from the left lane, and bicyclists to go straight or turn left from the right lane.

The greatest conflicts on bicycle paths or cycle tracks are at intersections. Vassar Street is unusual for a city street in that there is only one intersection (Massachusetts Avenue) in the one-mile long project area.

In his previous sentence, Mr. Smith mentioned two intersections. Now he claims that there is only one. In fact there are two, and there are driveway junctions as well.

The potential for conflicts have [sic] been minimized by transitioning the cycle tracks to bicycle lanes at this intersection. The cycle tracks also transition to on-street bicycle facilities at both ends (Main Street and Audrey Street).

Driveway entrances are called "junctions" rather than "intersections" in the technical literature; however, the technical issues with driveways are the same as at intersections. The path crosses the heavily-used driveways at the Building 39 portal and the West Parking Garage, as well as several others.

Mr. Smith describes the on-street treatment as mitigating conflicts at the Main Street and Massachusetts Avenue intersections. He is correct about this. It would have the same benefits at the driveways.

The Vassar Streetscape design as proposed is responsive to the needs of the majority of cyclists

Smith makes this statement without giving any supporting evidence. On safety grounds, this statement is contradicted by conclusive evidence. The Wachtel-Lewiston study, for example, showed that car-bike collision rates are higher on sidewalks than streets for all age groups, in a general bicyclist population..

Smith's statement also fails to account for the particular bicyclist population that uses Vassar Street. The MIT bicyclist population consists almost entirely of healthy young adults of high intelligence riding multi-geared, efficient bicycles. Sidepaths are only suitable for slow travel. Slow travel is typical of a European population riding heavy single-speed and three-speed bicycles. Smith is claiming that MIT students are not smart enough to operate bicycles according to the same rules of the road they use when driving motor vehicles or riding their bicycles elsewhere in Cambridge, but that on the other hand MIT students are smart enough to operate on a facility which is more hazardous and requires greater vigilance than the road.

...and recognizes the improved safety afforded by the transition to bicycle lanes at street intersections.

In other words, bike lane intersections are safer (I agree, and research bears this out), but sidepath intersections are nonetheless preferable at the driveways.

We believe this design fits the special conditions of Vassar Street, which are not typical of Cambridge. It is not meant to imply that the design would be appropriate throughout the city, where conditions are different.

Just what is different about Vassar Street as completely to overturn the results of a dozen safety studies? Mr. Smith doesn't say. Yes, Vassar Street is different in some ways, but Smith has done nothing to demonstrate that these differences make the proposed design preferable.

And also, who are "we"? Mr. Smith is a consultant who is supposed to be speaking independently in his professional capacity. Use of the first person plural does not reflect this professional posture.

Bicycle lane design

One-way bicycle lanes will be provided on Vassar Street at the Massachusetts Avenue and Main Street intersections (see figures 1 a, 1 b and 2). The bicycle lanes will be five feet wide and adjacent to the curb. Cyclists will travel in the same direction as vehicles in the adjacent travel lane, i.e., with the flow of traffic.

This is the least troublesome part of the project, other than that bicycle lanes to the right of right-turn lanes pose the problems discussed earlier. However, use of the sidepaths for two-way travel (see below) will lead to bicyclists' crossing the intersections against traffic. In other projects, the City of Cambridge has recommended bike lanes as helping to get bicyclists off the sidewalks and to discourage wrong-way travel. But here, the City is acceding to MIT's desire to put bicyclists on sidewalks, and will thereby encourage wrong-way travel.

At both the Massachusetts Avenue and Main Street intersections, an additional travel lane will be provided on Vassar Street:

•    On both approaches to Massachusetts Avenue, a separate left-turn only lane and through/right lane will be provided. The bicycle lane remains against the curb on these approaches. Vehicles turning right onto Massachusetts Avenue must yield to through cyclists, just as they would on a street with only one approach lane. The position of the bicycle lane is consistent with AASHTO design guidance.

The provision of an additional travel lane for right turns makes for a real improvement.

However, placing the bike lane to the right of the right turn lane is incorrect, and decidedly not consistent with AASHTO guidance. The results are not "just as with a street with only one approach lane." On such a street, drivers who are preparing to turn right merge to the right curb, and others, including bicyclists, who are going through or turning left, either overtake them on the left or wait behind.

A bike lane to the right of a right turn lane directs bicyclists to overtake on the right of right-turning traffic. Motorists must then yield to bicyclists in their right rear blindspot while also looking ahead and to the left for traffic in the intersection. That action is not reliably possible. Several bicyclists have been killed in the past couple of years in the Boston area when they attempted overtaking to the right of right-turning vehicles. Also, there has been a very serious and widely publicized collision (the Gladstone-Spring incident as reported by Paul Schimek, a PhD in planning from MIT) when a bicyclist overtook a car on the right and struck a pedestrian.

•    On the Vassar Street approach to Main Street, two approach lanes are provided on Vassar Street - a left/through lane and a right/through lane. In this instance, the bicycle lane also remains against the curb. Vehicles turning right onto Main Street must yield to through cyclists, just as they would on a street with only one approach lane. The position of the bicycle lane is consistent with AASHTO design guidance.

Again, the addition of a turn lane makes a real improvement but the placement of the bike lane is incorrect, and inconsistent with the AASHTO Guide and Massachusetts statutes. The bike lanes should either be put to the left of the right turn lane or discontinued before the intersections, so that bicyclists and motorists are directed to merge to the correct positions for their destinations.

Cycle track design

Between intersections, cyclists will travel on one-way cycle tracks located on each side of Vassar Street. The cycle track will be five feet wide with a two-foot shoulder/clear zone on the left side and a flush separator to the right adjacent to the sidewalk (see figures 3 and 4). The cycle track will be at the same elevation as the tree strip to the left and the sidewalk to the right. It will be a different material and color than the sidewalk. The entire area of tree strip, cycle track and sidewalk is raised above street level.

This is a "striped sidewalk" as described by Andy Clarke. The AASHTO Guide warns again and again about placing bicycles on sidewalks and sidewalk-like facilities. Some specific citations from the Guide:

  • Pages 8-9: Sidewalks generally are not acceptable for bicycling, bicycle facilities must not encourage operation contrary to the rules of the road; sidewalk routes to be considered only under unusual circumstances such as on bridges or where bicyclists are incidental or infrequent users.

  • Pages 11-13: Plans for new facilities should be reviewed to identify and resolve potential safety issues; bicyclists want to avoid the need for frequent stops; intersection conditions (including mid-block), maintenance; cost/benefit must be considered; operation contrary to traffic law should be discouraged -- the proposed sidepaths fail all of these tests.

  • Page 20: General recommendations against designating sidewalks, even very wide sidewalks not acceptable, yet another warning against facilities that encourage violations of traffic law.

  • Pages 33-35: Long list of operational problems. Especially see #3, motorists will not notice bicyclists approaching from the right; #6, bicyclists will still prefer the roadway, #7, motorists' false expectation that bicyclists on the sidepath will yield to them and #8, vehicles waiting to exit driveways will block the sidepath. .

  • Page 58: Reiteration of many of the same warnings stated earlier. The fact that AASHTO finds it necessary to repeat these warnings so many times may give a fair idea of their importance.

Returning to Smith's letter:

Cyclists would operate on the cycle track in a similar manner to how they operate in a bicycle lane on the street.

Remember this statement, I'll be referring to it below. This statement reveals that Mr. Smith does not know enough about bicycle operation to speak with any authority on the subject. Operating in a bike lane and on a sidepath are very different. In particular, the sidepath requires slow travel because its design and traffic mix do not allow bicyclists to travel at their normal speed.

Sign up for the bike: Design manual for a cycle friendly infrastructure (CROW, 1993) states that the preferred effective width of a one-way cycle track with a peak-hour volume in one direction of up to 150 bicycles is 1.50 meters (4.92 feet). The current design includes a 5-foot wide cycle track, a 1-ft wide paved shoulder on the left side of the cycle track and an area about 1-ft wide to the left of the shoulder that is also rideable. Thus, the total width of the cycle track and the rideable area to the left before the tree trunk is approximately 7 feet (2.13 m). According to CROW, "the rule of thumb for comfortable side-by-side cycling can be taken as: 1.00 m per cyclist." This means that cyclists on the Vassar Street cycle track have the possibility of passing or overtaking maneuvers, if necessary, without going into the walkway. In addition, a 12 inch wide separator will be placed between the cycle track and the sidewalk. This separator will be rideable.

These dimensions only say how wide a bikeway should be. They have nothing to do with the location of a bikeway, which is the main issue with this project.  These dimensions are smaller than the minimum AASHTO dimensions, and the use of the 1.00 mm dimension is misleading.. The 1.00 m is separation between cyclists. The total width occupied by a pair of cyclists riding 1 m apart is about 1.5 m or 5 feet. This includes no shy distance or space for weaving or crash avoidance.

In citing these dimensions, Smith assumes that traffic on the sidepaths will travel in only one direction. As I said before, that is fantasy. It's well-known, and discussed in the AASHTO Guide, that one-way bicycle paths are used in two directions if the designated facility for the opposite direction is at all less convenient. In the present case, the only alternatives to wrong-way travel for reaching the sidepath on the far side of the street are a longer route, or threading between parked cars and climbing up a curb. Bicyclists will therefore use both sidepaths in both directions. This problem has been described in more detail in materials previously presented to the project planners.

Several facets of bicycle operations on the cycle track are different than on-street operations. Each of these operational issues is explained as follows.

Operation on the cycle traffic is different in several ways from operation on the street, but two paragraphs earlier it was the similar to that on the street.

Separation from pedestrians

Signing, pavement markings and education will be used to inform bicyclists and pedestrians of their respective operating spaces, as is done for similar facilities in Europe. As described previously, there is over seven feet of rideable space on the cycle track and shoulders entirely separate from the sidewalk.

The left shoulder is grass with encroaching tree roots. The right shoulder is the one-foot wide painted stripe (AASHTO calls for two-foot rideable shoulders on both sides). Between them is the five-foot cycle track.

The available width is barely adequate for one-way overtaking, and as I have indicated before, two-way use of the cycle track is inevitable. The AASHTO minimum recommended width for a two-way bicycle path is 8 feet, with a two-foot rideable shoulder on each side. This provides the minimum lateral operating space for cyclists to allow overtaking. 12 feet is recommended. 16 feet are necessary for acceptably safe simultaneous overtaking with two-way traffic (equivalent to a four-lane roadway).

Furthermore, encroachment of pedestrians onto the cycle track and bicyclists onto the walkway will be the rule rather than the exception. This has been demonstrated over and over. To say otherwise is pure fantasy.

All signs and light standards will be located in the five-foot wide tree strip or verge.

That's good, except that the expense of removing the bikeway when it proves undesirable will be greatly increased.

For the most part, the sidewalk is eight feet wide and is also free of obstructions. The combined lateral distance for the separate bicycle and pedestrian facilities is 15 feet. We believe this is sufficient space to safely, accommodate both cyclists and pedestrians.

While the bicycle facility is above street grade at the same level as the sidewalk, it is not a "sidewalk bikeway". A "sidewalk bikeway" is a segment of sidewalk designated as part of a bicycle route. The standard design for a sidewalk (4 to 5 foot width with a 6" curb separating it from the street) cannot reasonably accommodate bicycle traffic and pedestrians. Studies have demonstrated that routing bicycles onto a typical sidewalk increases the likelihood of crashes between bicycles and pedestrians. Accident data related to sidewalk bikeways is not applicable to the Vassar Street facility. The Vassar Streetscape design proposes separate facilities for bicycles and pedestrians each of which meets the operational needs of the respective users.

Why isn't it a sidewalk? Because we paint a stripe down the middle of it and say it isn't. Call it what you want, this is a sidewalk bikeway. AASHTO specifically warns that wider sidewalks may be more hazardous because they encourage faster travel.

Furthermore, the widening of the sidewalks/sidepaths will be accomplished by narrowing the street. There will no longer be bicycle/motor vehicle lane sharing width in the street. This change will further encourage bicyclists to ride on the slower, more hazardous sidepaths.

One-way cycle tracks are used extensively in Europe and continue to be recommended in recent design manuals published in Denmark and the Netherlands.

It's about the third time Smith has made the one-way and Danish-and-Dutch arguments. I've already answered them. Sidepaths are not recommended in the United States, haven't been for over twenty years, and for good reason. The Pasanen and Wachtel-Lewiston studies which I cite show that even one-way sidepaths lead to more car-bike collisions than riding on the road, and riding opposite traffic is far more hazardous yet.

MIT has the opportunity and has made the commitment to educate students, faculty and staff on proper operation on the one-way cycle tracks and lanes.

Then what MIT must teach: Ride slowly so collisions with pedestrians aren't too serious. The car-bike crash rate for through travel on a sidepath is about 3 times at high at intersections and driveways when traveling with traffic, and 12 times as high when traveling against traffic, so be careful! Be VERY careful of blocked sight lines: doorways hidden behind groups of pedestrians, portals where a car might be coming out of a driveway where you can't see it, etc. etc.

Stop at every driveway and look over your shoulder, and walk across, because there is no other way you can be sure to avoid the motorists turning across your path. They also will have a hard time seeing you, because of the row of trees and the parked cars between you and them. Oh, and by the way, when you go ride in the rest of Cambridge, it's completely different: there you ride in the street and follow the regular traffic laws.

Remember that elsewhere in Cambridge and throughout the region, it's against the law to ride on the sidewalks in some places, and discouraged in most others.  And you must sign this waiver form to absolve MIT for any responsibility for possible crashes on the Vassar Street facility. Your medical coverage will take care of immediate medical expenses (though we can't be responsible for long-term care), and tuition is up $100 per term this year to cover medical insurance and liability insurance cost increases. Got it? Good.

Signing and pavement markings will be provided to designate proper use of the bicycle facilities.

Then a stop sign will have to be placed at every driveway. How many bicyclists do you think will put up with stopping at every driveway when they could continue without stopping in the street?

Bicycle parking facilities within the MIT campus will be placed in locations that are not only convenient to building entrances, but also easily accessible to driveways and mid-block pedestrian/bicycle crossings that provide ramped access to the cycle facilities on each side of the street.

That is nice, but irrelevant to the design of the sidepaths.

Driveway junctions

The design team has taken measures to raise motorists' awareness of the presence of cyclists where the one-way cycle tracks intersect driveways. A typical cycle track/driveway junction is shown in figure 5. At these junctions, cyclists will have the right of way.

Once again I ask: if the junctions with the major intersections are safer with the bicyclists in the street, then why go to all the trouble of creating driveway junctions which are more hazardous, and then go to even more trouble to try to mitigate the problems?

The driveway will rise to meet the elevation of the cycle track. Based on City guidelines, this will be a steep incline, where motorists must slow down. Motorists are required to yield to cyclists just as they yield to pedestrians at sidewalk/driveway junctions.

This gets to the crux of the matter. Bicycles are vehicles. They are not pedestrians. Bicyclists travel too fast for motorists to yield to them reliably at pedestrian-type crossings. Bicycles, like all vehicles, can not sidestep out of the way as pedestrians can. That is why the collision rates at sidepath/driveway junctions are so very high.

The steep ramp from the street onto the driveway will force motorists to slow down significantly when turning from Vassar Street onto a driveway. The placement of on-street parking on the north side of Vassar Street and trees on both sides of Vassar Street is being designed so as not to restrict motorists' visibility of cyclists when motorists are turning into a driveway.

No, being designed to mitigate this problem. Motorists do not have eyes in the back of their heads; bicyclists will often be traveling faster than the motorists and will approach in the motorists' right rear blindspot. Smith also describes no measures to mitigate the problem of motorists' exiting driveways, where the sight lines between bicyclists and motorists will be blocked by pedestrians, and by portals.

A 1993 German study showed that raised crosswalks reduced the crash rate on sidepaths from five times to only two times that when bicyclists used the roadway. Is that good enough?

Most of the driveways are lightly used. The bicycle facility will cross the busiest driveway at the Stata Center as a bicycle lane and will be painted blue to alert motorists to the presence of bicycles.

Several lightly-used driveways do not make up for the heavily-used ones at the Building 39 portal and West Parking Garage. Once again, and now for driveways rather than intersections: if the treatment at the Stata Center is desirable, why is it not desirable also at the other driveways?

Mid-block crosswalks

Several mid-block crosswalks are provided on Vassar Street in the project area. Some will be new and others are existing crosswalks that will be redesigned. Bicycle crossing areas will be provided on both sides of the mid-block crosswalks to allow bicycle movements between the cycle tracks on each side of the street (see figure 6).

Mid-block crosswalks are desirable but they do not resolve the issue of wrong-way travel on the cycle tracks. I've said it before: in order to use a mid-block crosswalk, a bicyclist must often either travel opposite the desired direction of travel, making a longer trip, or else travel the wrong way.


Transitions have been designed between the bicycle lanes and cycle tracks at intersections. In most cases the cyclist simply continues straight (see figure 7). In other cases a gentle curve in the cyclist's path is required (see figure 8). The transitions are described below for eastbound and westbound cyclists:


•    Beginning at Main Street, cyclists travel westbound in a bicycle lane between the curb and a wide travel lane. Then the bicycle lane ramps up and straight onto a cycle track. The tree strip begins at this point to the left of the cycle track.

•    Approaching Massachusetts Avenue, the cycle track ramps down and straight onto a bicycle lane. The first 75 feet of the bicycle lane is painted blue to alert motorists to bicyclists in this transition zone.

•    The bicycle lane continues on the far side of the Massachusetts Avenue intersection and then ramps up and straight onto the cycle track.

•    At the western end of the project, the cycle track will curve slightly to the left and into a short section of bicycle lane on the approach to Audrey Street. This short section of bicycle lane will also be painted blue to alert motorists to bicyclists in this transition zone.


•    Beginning at Audrey Street, cyclists travel eastbound in a bicycle lane adjacent to the curb. Then the bicycle lane turns slightly to the right and ramps up onto a cycle track. The tree strip begins at this point to the left of the cycle track.

•    Approaching Massachusetts Avenue, the cycle track turns slightly to the left and ramps down onto a bicycle lane. The first 90 feet of the bicycle lane is painted blue to alert motorists to bicyclists in this transition zone.

•    The bicycle lane continues on the far side of the Massachusetts Avenue intersection and then turns slightly to the right and ramps up onto a cycle track.

Mr. Smith neglects to mention that the bicycle lane passes behind a truck loading zone at the Metropolitan Storage Warehouse. Truckers attempting to unload across the barrier-separated bike lanes in New York City in 1980 are one of the issues that led to the lanes' removal after only a few months. Another of the issues was a rash of fatalities due to motor vehicles' turning across the barrier-separated bike lanes, which are operationally similar to cycle tracks.

•    At the eastern end of the project, the cycle track will curve slightly to the left and ramp down onto a bicycle lane. The first 100 feet of the bicycle lane is painted blue to alert motorists to bicyclists in this transition zone.

No transitions would be necessary if bicyclists were routed outside the line of parked cars..

Pavement Design Features

The pavement system used in the Vassar Streetscape project has been designed to avoid problems that can be caused by tree roots interfering with pavements in cycle tracks, in particular heaving and cracking caused in the pavement surface by shallow tree roots. The causes of these problems are simple, and the solutions are equally simple and direct. Tree roots can quickly become confined in a traditional tree pit, which offers no escape from the area immediately surrounding the tree to other areas where they can take up water and nutrients. Root growth often becomes aggressive, seeking out any available pathway to reach new sources for the nourishment of the tree. As most soils under pavements are placed at a high compaction to prevent settlement, roots cannot force their way through. Often, roots find a layer immediately beneath the pavement where they can penetrate, by pushing the pavement up. As the size of the root increases, the "heave" in the sidewalk also increases. Where rigid pavements (such as concrete) are used, roots can lift and eventually crack the entire pavement section. Flexible pavements (such as bituminous concrete) lift only immediately above the root, and eventually "tear" the pavement.

The solution is to provide a medium underneath the pavement surfaces that will allow roots to pass through without losing the structural capacity of the soil. The Vassar Streetscape project includes a "treeway" system beneath the tree strip and the bicycle path. The treeway consists of a soil that is a blend of a coarse mineral soil (which provides the structural capacity) and organic matter. The mineral soil creates a series of voids in its matrix which are filled with the organic matter; roots are then able to infiltrate through the voids and access nutrients and water stored in the organic matter. As the voids are already created in the matrix, the roots do not displace any soil, and thereby do not create reflective cracking, heaving or tearing of the surface. Also, scientific studies indicate that roots tend to grow at the lower levels of such a matrix (in the case of Vassar Street, the matrix is approximately two feet thick), further isolating the surface from impacts of root growth.

That does answer one of my comments -- if it in fact works. That is, if the soil maintains its special properties throughout the life of the project.

Snow removal from the combined sidewalk/cycle track area should be significantly improved since the combined width of the surface (over ten feet wide) will allow the use of larger, more efficient equipment.

Note the dangling comparison. Improved over what? Smith doesn't say. I'd say, improved over a narrow sidewalk but still far worse worse than for a street. For a surface to be suitable for bicycling in winter, it must be clear of snow and ice. Drainage and drying of the surface occur spontaneously after plowing of a street, because streets are crowned and have drain inlets. The sidepath will have no drain inlets, and it cannot be graded so water runs off longitudinally from all points. Snow that piles up between the sidepath and street, (whether cleared from the street or the sidepath, or both) will form a dam. Snow will melt onto the surface of the sidepath and then will freeze. Heroic measures -- manual excavation of snow from between the trees in the tree strip, and the use of large amounts of melting chemicals (which also damage bicycles and the pavement, and kill trees) would be necessary to keep the sidepaths open in the winter.

Repeated attempts have been made to keep some bicycle paths in the Boston area open in winter, and they have never been successful.


The streetscape project will include new and separate facilities for the exclusive use of bicycles.

Nonsense. Not exclusive. Shared with pedestrians and inline skaters, and crossed by driveways at intersections which make for more hazardous encounters with motor vehicles than when riding on the street.

Currently bicycles operate in the street in shared travel lanes with motor vehicles.

Good. Keep it that way, or maybe stripe bike lanes. End of problem. Cheap, simple, no liability risk, no special maintenance needed.

The new design includes one-way cycle tracks, which separate cyclists from motor vehicles along sections of the street between intersections.

Notice that Smith does not mention any advantage of this treatment. Neither has he done that anywhere in his report. Perhaps he knows enough not to, as there is none. In fact, the project results in a great increase in expense of both construction and maintenance, and a high crash rate. The great majority of car-bike collisions occur at intersections, and intersections (primarily those with driveways, in this project) become far more hazardous. Collisions between bicyclists and pedestrians also become a far more serious hazard.

At intersections, the bicycle facility transitions onto the street as bicycle lanes. While a variety of different design solutions are available for any project, MIT and the City have chosen to try a different solution on a unique section of Vassar Street through the center of the MIT campus. We believe that this design is appropriate for cyclists who will travel along Vassar Street.

You ("we") may believe whatever you want. However, a public works project, just like a medical treatment, must reflect scientific evidence rather than unsubstantiated opinion. It is not reasonable or ethical to use MIT students as experimental subjects for a failed treatment option, or to put the Institute in the position of having to pay for both the treatment and the consequences of its failure. The sidepath treatment flies in the face of national standards, is slower, more hazardous, more expensive, and far more difficult to maintain than the alternative, and poses a serious liability risk for the Institute.

A claim that has been made by the project's proponents that it will encourage bicycle use. True enough, this treatment might fool some people into thinking they are safer than they would be with an on-street treatment. A few more people might ride bicycles, but only a few, because parking restrictions make private motor vehicles impractical for trips around the MIT campus in any case. Any increased bicycle use would only be a tradeoff against  use of MIT shuttle buses, and walking.

This project amounts to a "Pied Piper of Hamelin" approach to bicycle planning: build it, people will supposedly be foolish enough to use it, and if you rack up a few fatalities and disabling injuries, and a million-dollar lawsuit for the Institute, well, it's all for the greater good of the Utopian vision of a car-free city, right?

No, it isn't. I've been a utility bicyclist for 38 years and a bicycling activist for 25 years. I'm in favor of reducing motor vehicle use in cities too. But I must reject projects that 1) objectively reduce bicyclists' mobility; 2) put bicyclists and others unnecessarily at risk when safer alternatives are available and 3) in any case, do nothing to reduce use of private motor vehicles. The Vassar Streetscape project is one of the worst I have ever encountered on all of those counts.

Summary: what Smith does and not say

Mr. Smith's statements in support of the sidewalk are rife with contradictions, prevarication and outright falsehoods, as I will show.

Mr. Smith has for the most part ignored my previous comments rather than to answer them, and he has in every case ignored the research data I presented, rather than to try to refute it. Smith's report consists mostly of a description of the project. He does not answer, and does not even address, any of the following questions.

  • What crash rate do you anticipate for bicyclists who use the path, and based on what evidence?

  • How does this compare with the crash rate you would anticipate for alternative treatments?

  • You say that these facilities must be all right because they are used in Europe. Does that mean that they are the state of the art in Europe?

  • What liability risks do you anticipate for MIT and for the City?

  • How can you rate the cost/benefit of this project versus alternatives?

  • What is the design speed of this facility vs. that of alternatives?

  • What changes in bicycle use vs. use of motor vehicles, walking and public transportation do you anticipate as a result of this facility, and based on what evidence?

  • What happens to cyclists who want to use the road?

I'm waiting...

John S. Allen VI '75


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