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What I (and Others) Have to Say About Bicycling

Most of the writings here were originally posted to the
misc.transport.road and rec.bicycle.soc USENET newsgroups,
or to the mailing lists now hosted by Topica.

Bicycle Traffic Control:

Jim Gregory once wrote:

Our local bicycle committee is working to reduce the number of accidents that occur where bicycle paths cross major streets. One particular problem occurs where a bicycle path crosses a street at a T-intersection. At these Ts, motorists have to turn left or right, while pedestrians and bicyclists on the bicycle path proceed straight across. Motorists expect to have the right-of-way, and often don't notice motorists or pedestrians trying to cross. Our city traffic engineer is unwilling to allow a "pedestrian-bicycle-only" cycle in the traffic lights at these intersections, arguing that it would be too long a delay for motorists to wait and would interfere with the synchronizing of the traffic lights on this segment of roadway.

(The intersection) looks like this:

(Adapted from

The problem is that left-turning motorists from the roadway at the bottom of the diagram interfere with bicyclists and pedestrians trying to cross the four-lane road at the same time. We have three intersections like this in town. There is a pedestrian walk light at everyone of these intersections, but incredulously, the pedestrian light is on "walk" at the same time as motorists at the bottom of the diagram have a green light, too. In other words, motorists turn left at the same as pedestrians and cyclists try to cross. Again, our local traffic engineer is unwilling to allow a bike/pedestrian only cycle in the traffic lights, as he argues that motorists on the four-lane road would have to wait for both a motorist and a bike/pedestrian cycle (which would take too long), and any kind of pedestrian light that was activated only when pedestrians or bicyclists were present would throw off the synchronization of other traffic lights along the four lane road.

I responded:

I can understand the argument regarding not wanting to add another phase to the cycle, especially given the desire to maintain progression on the cross street.

Also, if the intersection is near capacity, the green time loss for a separate "bike-only" phase could affect the intersection level of service.

More on the drawbacks of "bicycle-specific" signals later.

Our city has no intention of replacing the bike paths with lanes. Note that, even if a parallel on-street bike lane were built, pedestrians would still face the same problem.

The best solution by far for safe and convenient bicycle travel would indeed be to remove the parallel separated pathways and to integrate the bicycle traffic with other vehicular movements.

Pedestrians, however, have different operating characteristics than bicyclists. They can stop and turn instantly, and their cone of vision is far less constrained (a typical pedestrian can turn his/her head to the side without swerving in their path, unlike many bicyclists).

Add to this the fact that bicyclists' approach speeds to this intersection may be 3-4+ times higher than pedestrians, ensuring that there is no way for the conflicting movements to have adequate sight distance.

This is why a pedestrian WALK signal phase running concurrently with the T street green phase may perform acceptably for pedestrians (depending on volume) but may not be acceptable for bicycle crossing, unless bicyclists dismount and cross as pedestrians - which will be an unacceptable inconvenience for cyclists.

In addition to this problem, what about improving safety in the more common circumstances where bicycle paths cross streets or driveways? Again, our city council and public works department has made it clear that they will not tear out any bicycle paths to replace them with bike lanes. Given this (unfortuate) fact, our bike committee is seeking suggestions for bicycle safety or public information campaigns, signage, etc. We specifically would like to know what has worked and what hasn't.


This is the precise reason that sidewalk and parallel pathway cycling has shown a significantly higher rate of motor vehicle-bicycle collisions. See Wachtel and Lewiston's article in the September 1994 ITE Journal for examples. Also, the AASHTO Guide for Development of Bicycle Facilities cites similar examples (among others) for why parallel separated pathways are officially discouraged.

I don't know of any effective signing to treat parallel pathway crossings. Denver, CO has used a variant of the W10-3 sign for this purpose (substituting a bike symbol for the tracks), and is considering submitting this sign to the Bicycle Technical Committee of NCUTCD for possible inclusion in the MUTCD.

Existing W10-3 sign

Proposed Denver sign

My problem with the use and/or adoption of such signs is threefold.

Now, getting back to bicycle-specific signals:

In order to establish a phase solely for bicycle (and pedestrian) traffic, you have to rob green time from the other phases in the cycle (assuming that the bicycle-specific phase is called). This by itself reduces the capacity of the intersection for all users.

Now, add into this the implicit assumption that bicycle traffic must be stopped on all other phases except the bicycle-specific phase. This greatly increases delay to pathway users, who could otherwise proceed at the same time as other traffic in the same direction. This also assumes the pathway users would obey the signal - not always a safe bet.

Also, this promotes non-uniformity of traffic control for bicyclists and pedestrians. They will be expected to operate in a different manner at the few locations controlled by these signals. More important, if they behave in the same manner at "normal" intersections, they may be in very real danger of collision and injury.

One of the few reasonable applications of such a bicycle-specific signal would be to "fix" an already "broken" situation, such as what's described here. It's my understanding that Davis, California has installed a bicycle-specific signal at a location generally similar to this one.

Now, because Davis (and other cities, see below) are using a bicycle-specific signal in a very limited application, groups in other cities may be thinking, "how can a bicycle- specific traffic light help us too"?

What I'm afraid of is that such a signal will be used in inappropriate ways, such as to "help" bicyclists make left turns from the far right side of the road in certain locations (which indeed has been proposed for installation in a certain East Coast city).

One of the fundamental principles of traffic engineering is uniformity. Road users should always be encouraged to behave in a similar manner in similar situations. For example, regardless of whether a signal is present, drivers are encouraged by signing and marking to turn left from the far left lane.

Now, compare this to the example cited above, where the bicycle-specific signal is encouraging left turns from the far right lane. What will happen to the poor cyclist when he or she does the same thing in the absence of such a signal? Ouch.

I fear that if bicycle-specific traffic signals gain widespread adoption or are incorporated into the MUTCD, that they will be used much more in an inappropriate manner than a correct manner - regardless of whatever guidance is included in the Manual (just look at how standard signals are sometimes misused).

Unfortunately, not everything bicycle-specific is necessarily bicycle-friendly.
By the way, this is the topic of my presentation at the 1999 ITE Annual Meeting.

P.S. Tucson, Arizona is also installing a bicycle-specific signal, but for a much more straightforward reason (literally!) - to permit bicyclists using a street to go straight through an intersection, while requiring motor vehicle traffic to turn left or right. This application is much less hazardous that the ones described above, and is much more in keeping with uniformity of traffic control.

After printing this, James Mackay of Denver, Colorado responded:


Took a quick look at your website and was pleased to see that you had our Trail/Crosswalk warning sign on it.

I certainly recognize the potential for abuse of these signs, resulting in cheap, ineffective illusions of 'safety". You heard me tell our Bicycle Technical Committee that "I am not the biggest fan of sidewalk bicycling" IMHO putting bikes on sidewalks can create more problems than it solves.

But I do think that these signs have a role to play in making things more bike friendly. The swiss have a similar version for two-way bike on sidewalk type conditions. Boulder CO has a sidewalk type bikeway that will probably always have college student motorist versus college student bicyclist type conflicts at the crosswalks. Phil Miller of King County WA expressed interest in experimenting with these signs on a rail trail directly adjacent to a road - there apparantly was little potential to re-align any of the intersections.

Yes, but unless the signs have a measurable ability to reduce crashes at these locations, then I (and also probably FHWA) would be very reluctant to approve such a sign, given the safety record of these types of intersections.

That still doesn't address the other problems noted, namely:

Have you seen the March 1999 issue of Bicycling Magazine? In their write up on Denver on page 57 they included the same image of the sign and labelled it "A sign of respect". Given their usual "triathalon aero bars and paint jobs" fixation, I found this a bit encouraging. the same way that a W10-3 increases respect for trains?

The sign might also be sending another clear message - a message to both motorists and cyclists that it's OK to ride against traffic, and not only in the places where the signs are placed.

Perhaps the real issue may become to make sure that these signs aren't used as a substitute for good sight lines, well demarcated crossings, and motorists who care about bicyclists. Then again, gettting cyclists to break their cadence, ride defensively, and (on occasion) squeeze their brake levers should be encouraged as well.

All these are desirable, but they still do nothing about the fundamental problems inherent in these crossings. The clearest possible sight lines will still be worthless if they are in directions that drivers and cyclists simply do not look.

Let's keep the dialogue going. I don't want to create illusions of safety. While I recognize that sometimes doing nothing is better than making things worse, I would like to think that these signs can provide a net improvement.


It would be much better if this could be supported by good research, prior to approval of the use of these signs across the US.

I'm not knocking you at all for trying to solve the problems with these intersections. I do however fully anticipate that these signs would be used to rationalize installing even more of these intersections, instead of selecting treatments with much better safety records.

(Note: In the years that I have known him, I have gained a full respect and appreciation for Mr. Mackay's professional judgment and unswerving devotion to making things better for cyclists across the US. In fact, he does come up with a darn good idea now and then. ;) I just honestly believe that the downside to this particular concept greatly outweighs the benefits, and that is why I posted my commentary on the idea (NOT the author)).

Finally, there are many individuals in the cycling community that are not members of NCUTCD or other official groups that have a stake in the development of new signs and other devices. This is especially relevant given the interest that advocates and others have shown in wanting to adopt "innovative" traffic control for bicyclists - sometimes before the final research results are in.

Innovation isn't inherently bad (how else would we improve?), but it needs to be looked at from all sides to avoid making costly mistakes that might take years to fix.

Onward with the dialogue! :)

Cyclists' Rights:

"sharx" wrote:

Sounds as if the lunatics have taken over the asylum there. The average car owner pays many times more taxes than the average cyclist and THIS is what they get for it??

I responded:

A person's right to travel on non-controlled-access public highways is not proportionate to size or amount of taxes paid.

If this was so, the all those poor little car and pickup/SUV drivers had better get out of the way of those large trucks, who weigh much more and pay much greater user fees.

Now I'm no big fan of certain methods of "bicycle-specific" traffic control, but understand clearly that cyclists have a fundamentally established right to use roadways in a safe and legal manner.

"sharx" replied:

What kind of idealistic pretend world do you live in? MONEY talks and (BS) walks.

Actually, it's the world that I live in - AND work in. When I design traffic engineering features for roadways, I take into account the needs of all legal users, including those without motors.

This is fully supported and reinforced by agency policy -it's not just my opinion.

If this was so, the all those poor little car and pickup/SUV drivers had better get out of the way of those large trucks, who weigh much more and pay much greater user fees.

Yeah, but there are a lot more voters driving cars than the large trucks. And a lot more contributors to political funds are driving cars, not trucks or bicycles.

I won't disagree that the majority of road users do drive cars and trucks, but don't mistake unequal volumes to mean unequal rights.

As I noted earlier, certain road users, such as bicyclists, have had their right to use public roads affirmed by more than a century of legal precedent and highway law.

When jurisdictions have unfairly restricted cyclists' rights, cycling groups have often been successful in court challenges to such laws.

Of course, since they are not required to have any license plate on their bike,there is no way one can report them to the police. We need COMPULSORY bike registration and insurance. Also, we need cyclist licensing. They WANT all the rights of motorists..they should also pay out similar costs.

OK, let's take this proposal seriously.

A generally accepted principle of road use taxation is the concept that a vehicle should pay its fair share of the impacts it creates on the roadways.

For example, heavy trucks pay fees based on weight, since roadway damage increases exponentially with axle loading - e.g. one 80,000 lb truck creates about 2000x the damage of a typical passenger vehicle.* Therefore, the truck pays significantly more in user fees.

By this criterion, bicyclists should pay nothing, because near-infinite bicycle loadings would create essentially zero pavement damage.

There are of course other services provided to road users, such as traffic control, police services, etc. Also, there are the hidden costs of motor vehicle use, such as negative environmental impacts. However, there is such inconsistency in even estimating the full cost of such services that setting up an equitable system for non-motorized users would be very difficult.

A local group recently examined the question of user fees for bicyclists. The conclusion was that such a fee system, if it was set up with fair and proportionate fees, would not come close to recovering the administrative and enforcement expenses necessary to ensure compliance by bicyclists across the state.

Finally, the concept of requiring bicyclists to carry insurance is incorrect, as bicyclists have far less potential to create property damage, injury, and death to other that motor vehicle drivers do. Remember, when you're driving, you're operating heavy equipment at high speed - cyclists are not.

When bicyclists do damage or injure others, the current system of liability has seemed to be effective - there's not a huge problem with uninsured cyclists, as there is with uninsured drivers.

*from the AASHTO table for equivalent single axle loads (ESALs)

"Bike Paths":

Mike Spack originally asked:

Owners of an apartment complex for senior citizens are concerned about the safety implications of a trail that will be built between their parking lot and the road the lot accesses. The three parking lot driveways access a county road with moderate traffic levels. The public hearing process has been concluded for the trail project and the construction plans are nearly complete. The trail section will be a 12 foot bike trail adjacent to the back of curb, a 3 foot grass separation, and then a 6 foot pedestrian trail. This trail section will cross the three driveways that are used to access the apartment parking lot. The trails will have stop signs at the driveways and 4" white lines will delineate the trails across the driveways.

The owners concern is that the senior citizens will end up in accidents trying to cross a 21 foot trail section with bicyclists and roller bladers zooming by, then immediately trying to get out onto the county road. Some of the senior citizens are uncomfortable getting out of the parking lot with current conditions. The owners of the apartment complex are asking for suggestions on how to improve the situation. The county is willing to incorporate our suggestions into the plans, short of changing the section or location. I appreciate any suggestions on how to improve the safety of this situation. THANK YOU!

Gary Vlieg replied:

Have you considered putting in pedestrian baffles on the ped trail and bollards on the bike trail where they cross the drivways? And perhaps put speed humps on the driveway on either side of the trail.

Is there sufficient queue storage between the road edge and the first trail to allow one or two vehicles to queue without impeding the trail?

I think that the issue at hand is the conflict point and you need to ensure that the drivers/pedestrians/cyclists all have sufficient opportunity to see each other to prevent a potentially fatal conflict. In my mind the best way to achieve this is to slow everyone down. Given the concerns you noted, it seems as though the seniors are cocerned with having to make a number of critical decisions within a short time and space therefore try to give them more time and more space....

One persons opinion......

Riley Geary responded:

Do folks on this list still think bollards are appropriate structures on trails or paths intended to be used by bicyclists--either for preventing motor vehicle access to such facilities, or to induce those bicyclists to slow down when approaching an intersection where motorized traffic may be present?

We certainly don't put trees or other potential obstacles for motorists to avoid in the middle of a travel lane to try and traffic calm our roads, so why has this practice been allowed when it comes to off-road bicycle facilities?

Have any studies looked into the safety hazards bollards represent to relatively high-speed trail users such as bicyclists and in-line skaters, particularly at night when they may be much more difficult to detect?

I gather at least some bicyclists who have been injured in collisions with these fixed objects have successfully sued the agencies responsible for their installation. Are there any case summaries of the legal issues involved that anyone can point to?

Mr. Vlieg replied:

It is obvious that you disagree with me regarding the bollards and baffles, which is your perogative. Nonetheless I maintain that these are viable options and yes we do install similar structures on roads - I refer you to chicanes, roundabouts, diverters etc.

As a cyclist and as a vehicle driver I have observed NUMEROUS instances of cyclists and in-line skaters (not to mention vehicle drivers) ignoring traffic control devices that are installed for their protection. Installing a well marked and well illuminated physical barrier that serves to slow down the skaters and cyclists, forcing them and others to look for conflicting traffic, is in my opinion, a good thing. As you note yourself, the cyclists and the skaters are relatively high-speed trail users - you have got to slow them down at the conflict points.

Note please that I also recommended some physical intrusions for the automobile traffic in an effort to have them recognise the conflict area that they were to enter.

Colin Kinton then added:

You are correct a cyclist will not ignore a bollard in the middle of the path. However, as a cyclist, I sure would not want to run into one of those things. As a motorist, if I loose control and run into a chicane, I risk injury to my vehicle. We do not use bollards for traffic calming of motor vehicles. I think by comparing chicanes to bollards is the apples to oranges situation. Maybe as transportation professionals we can find traffic calming devices for cyclists which won't kill them if they loose control.

If the cyclists are ignoring standard traffic control devices, the answer is not "@#$%, we will MAKE them obey the traffic control devices, or else."

Finally, Bob Streicher ( makes the observation:

First of all, if I understand your description correctly, the bike path is immediately behind the curb. If this is true, this can be very dangerous for cyclists using this path. Assuming this a two-way path, cyclists traveling in the reverse direction to the adjacent vehicle lane will get squeezed by an oncoming cyclist on their immediate left and oncoming vehicles on their immediate right. This is not a particularly comfortable position to be in, especially if you have young kids on their bikes, who have a difficult time traveling in a straight line during the best of times, and/or if the travel speeds in the traffic lane are fairly high (I've been caught in situations like this). You need to separate the path from the edge of the road!

My second comment relates to whether this pathway is appropriate given you have a number of driveways to cross. My position, as a regular cyclist and with being involved in planning cycling/recreational pathways, is that where you have a number of driveways or intersecting streets, you are likely better off without the pathway - having the cyclist on the street. Every such driveway is a conflict point for cyclists and other vehicles, where the rules of the road are not well understood by either party, and where the presence of a cyclist is not expected by the motorist. With the high rates of speeds that can be achieved by some cyclists (they will not STOP at these driveways), there can be significant conflicts. There was a good article in the ITE Journal some 3 or 4 years ago indicating the much higher collision rates with off-road facilities which act essentially as sidewalks. If you need, I could try to find this.

If possible the pathway should be built along an alignment which avoids having to cross these driveways. If not, and if there are a number of other similar conflicts along the path, I would question whether you should build it. As a minimum, have it separated from the edge of the road.

Looks like we have a problem here - and I'm not just commenting on the tone of the discussion.

I fully agree with a number of the correspondents that parallel separated pathways make very poor bicycle facilities.

The AASHTO Guide to Development of Bicycle Facilities lists all the problems with these types of pathways. (pp. 22-23, 1991 edition; pp. 39-41 and 52-53, 1999 draft ed.)

The only type of collision that this type of pathway can possibly reduce is the motorist-overtaking type crash. This crash type makes up about 8% of motor vehicle-bicycle crashes, and less than 2% of total bicycle crashes.

Conversely, this type of pathway greatly increases the risk of crashes at driveways and intersections by introducing bicycle traffic at unexpected and difficult locations. Intersection and driveway-related crashes already comprise 70% of all motor vehicle-bicycle crashes - these pathways only increase the problem.

This is a very real liability issue. There is no shortage of expert witnesses who would appreciate the opportunity to instruct a judge and jury on the deficiencies of these designs - at the expense of public agencies and engineering firms.

Diagrams and examples of the conflicts inherent in these facilities at intersections and driveways (such as the one in question) may be seen in a recent paper of mine on bicycle facility design. (You will need a PDF document reader such as Acrobat Reader to view the presentation - see

The study that Bob refers to is: "Risk Factors for Bicycle-Motor Vehicle Collisions at Intersections", published in the September 1994 ITE Journal.

So, if we know that these pathways have deficiencies, why are they still being designed and built?

(OK, I know you all know the answer - politics, stated community preference, misconceptions about relative risks, accommodation of other non-motorized modes, etc...)

If anyone asked... I would strongly recommend to the agency developing the trail the following courses of action:

  1. Build a pedestrian path (e.g. sidewalk) adjacent to the road, and build on-roadway facilities for bicycle traffic.

  2. If this is not feasible, then do not sign the parallel pathway in any way that encourages bicycle travel or indicates that it is a preferential bicycle facility. This may help in dealing with the liability issue, as the agency is not inviting the bicyclist onto the problematic facility.

I fully understand that significant changes in project scope may not be feasible at this late date, due to funding restrictions, clearances, etc.

However, these issues should be kept in mind for any future projects where a pathway is considered.

Now, for the second issue - can traffic control devices help at these pathway intersections?

First, some comments based on observation and experience:

  1. Bicyclists on separated parallel pathways can be expected to disregard stop/yield signs if they unreasonably interfere with through travel, or assign right of way in a manner not keeping with generally accepted traffic flow principles; e.g. stopping a through route for a driveway, as in this example. (The 1999 edition of the AASHTO Guide also discusses this issue).

  2. Stop/yield signs on separated parallel pathways have dubious legal standing. The cyclists are proceeding parallel to the main roadway - are they through traffic, or not?

  3. Motorists will generally disregard set-back stop lines at intersections and driveways, and instead pull up far enough to see down the crossing street to enter or cross that street, as years of driving experience has hard-wired them to do.

Now, add in a large percentage of elderly drivers at the driveway in question. This only adds to the problem.

As a traffic engineer who deals daily with signing and marking issues, I have little faith in the ability of traffic control devices to greatly change or contradict ingrained operator behavior.

Placing a sign at a pathway crossing is realistically not going to change the tendency for drivers at intersections to only look in the directions where they have been trained to look by many years of experience.

Not only that, placing such a device is making a promise to the pathway users that drivers at the intersection will look out for them - and that's a promise that sign can't keep.

Finally, regarding the speed of the pathway traffic at the intersection or driveway:

As noted above, path users will tend to operate in a manner in keeping with the facility type. If the path is parallel to a through road, then the users may rightly feel that they are through traffic as well, regardless of signs to the contrary.

Placing bollards or other obstructions in a pathway for the purposes of speed control is questionable from an operations and liability viewpoint.

The new AASHTO Guide does recognize the use of bollards as a treatment for pathways, but only for the purpose or restricting motor traffic on the pathway - not for speed control.

As for the pedestrian traffic - peds can stop and turn instantly, and have a wider field of view, unlike bicyclists. Placing physical restrictions on pedestrians at intersections and driveways may not have the desired effect, and may be counterproductive.

Placing physical restrictions on bicycle traffic at every conflicting intersection and driveway destroys the effectiveness of the pathway as a transportation facility, and still may not have the desired effect on pathway or roadway users.

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Updated 01 April 2005

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