Friday, January 23, 2009

Review of John Forester's talk at Google headquarters

John Forester's talk at Google HQ, May 17, 2007

I wrote this review in May 2007. A friend just brought it to my attention, and I figured I would post it here.

John's basic point was that bike lanes and bike paths are not consistent with vehicular cycling. He described vehicular cycling as
  1. First come, first served (leave room in front of you and don't cut drivers off)

  2. Ride on the right side of the road

  3. Between intersections ride to the right (if safe) and don't impede other traffic if you don't have to

  4. When entering a road or changing lateral position, yield to traffic already on the road (don't dart out) and look over your shoulder before changing lanes

  5. Get into the appropriate position at intersections (left to turn left, right to turn right, and in between to go straight

But he skips right past his opinion that bicycles and cars can mix safely. I myself am a vehicular cyclist, so I happen to agree. Perhaps John thinks that his opinion (that vehicular cycling is safe) is so obvious that it goes without saying, but most people disagree.

I find that those who have opinions about cycling on public roads appear to be in one of two camps: those who think that bicycling around cars is dangerous no matter what and therefore bicycle facilities are needed to segregate cyclists and cars, and those who think that bicycling around cars is not dangerous when cyclists follow the rules of the road. In my experience I have encountered many more people in the former camp than the latter. In discussions with people in the former camp I think that most do not know how to follow the rules of the road on a bicycle and cannot imagine that it is even possible (particularly for children). This is a major bone of contention. He says it is easy to follow the rules of the road and it is easy to teach, while most bikeway advocates think exactly the opposite. It is not possible to design a single road network that satisfies both camps.

He points out that another reason for bikeways is so that drivers will not be inconvenienced by slower bicyclists. Recall that John first got involved in bicycle politics when the City of Palo Alto established mandatory sidewalk use along Oregon Expressway, so his point is well taken. But that does not make such efforts a conspiracy in favor of cars. (It is also true, for instance, that the main purpose of left turn lanes is to keep left turning cars from interfering with through traffic, so this kind of thought is common in traffic engineering.) Most engineers who design sidepaths, for example, think that they are doing bicyclists a favor. That's a lack of knowledge, not a conspiracy. There is a saying, "Never ascribe to malice that which can be explained by incompetence."

John made an interesting point about cyclists positioning themselves to make turns at intersections, He said that he favors right turn lanes because they allow drivers to get themselves into position before reaching the intersection. I agree.

He briefly mentioned that it is unrealistic to expect children to position themselves correctly at ramps (he calls them high speed right hand curves). I am not a child and I find it difficult to position myself at ramps and much prefer right angle intersections.

John makes the questionable assertion that a white stripe does not help with positioning of cars and bicycles between intersections (he was arguing against bike lanes). Traffic engineers know that drivers tend to follow stripes; that's why we use them. In my experience, I have found that longitudinal stripes improve positioning a lot.

He also dismissed people's fear of taking the lane when cycling in a narrow lane, saying that drivers simply won't run into you (he joked that they don't want to scratch their paint). He quoted the small percentage of bicycle accidents that involve being hit from the rear, but left out the fact that most result in serious injury or death, making it a big deal. John is an advocate of wide outside lanes, so I do not understand his lack of empathy with most people regarding their fear of being struck from behind.

Saturday, May 3, 2008

Review of NCHRP Report 500, Guidance for Implementation of the AASHTO Strategic Highway Safety Plan

I just took a look at NCHRP Report 500, Vol. 18, titled A Guide for Reducing Collisions Involving Bicycles - Guidance for Implementation of the AASHTO Strategic Highway Safety Plan. The lead authors are Craig Raborn of the University of North Carolina Highway Safety Research Center and Darren J. Torbic of the Midwest Research Institute.

In the introduction, the report states

Bicyclists are recognized as legitimate roadway users. ... The safety interests of bicyclists are sometimes in conflict with the interests of motorists. This conflict arises primarily from the substantially different characteristics of the two modes of transportation. Although bicycles can be ridden on most types of roads, the design interests of accommodating higher motor vehicle traffic volumes and speeds during peak hour congestion may create conditions that are less safe for bicyclists. This guide includes road treatments, countermeasures, and other options that support a balanced transportation system.

Safety concerns can significantly influence a person’s decision to bicycle for transportation or recreation. Bicyclists inherently understand that they are vulnerable road users. However, understanding bicyclist safety issues has proven difficult for engineers, planners, and facility designers. Traditionally, safety problems have been identified by analyzing police crash reports, and improvements have been made only after crashes have occurred. Such methods are not sufficient to fully understand and effectively address bicyclist safety concerns; waiting for crashes before responding with countermeasures carries a high price because many bicycle crashes tend to be severe.

First the report says that "bicyclists are legitimate roadway users," then it says that the "design interests of ... higher motor vehicle traffic ... speeds ... may create conditions that are less safe for bicyclists." So the report's stated motivation is safety for bicyclists. (The report says nothing explicit about slower bicyclists delaying higher speed motor vehicles.)

The closest thing I could find of an analysis of why higher traffic speeds create a hazard for bicyclists was this on page III-1:

Speed influences both the severity of crashes that occur as well as the likelihood of occurrence, and has been identified as a contributing factor in all types of crashes. ... Bicyclists are vulnerable road users, and the impact of higher speeds on crash severity is obvious.

Also, in the discussion of Share the Road signs:

The safety effectiveness of shared roadway signs has not been evaluated, and their overall use is thought to be decreasing. Some experts now feel that they are only appropriate in “pinch point” locations where roadway facilities may not fully accommodate both bicyclists and motorists. ... These signs are typically placed along roads with significant bicycle traffic but relatively hazardous conditions for riding, such as narrow travel lanes with no [paved] shoulder, roads or streets with poor sight distance, or a bridge crossing with no accommodation for bicycles.

So hazardous conditions for bicyclists include narrow travel lanes with no paved shoulder. The report does not explain why, other than to say, "the impact of higher speeds on crash severity is obvious."

In analyzing the risks of various types of bicycle accidents, the report states that in a study done in 1996, motorist overtaking cyclist accidents made up 8.4% of total reported bicycle crashes.

The report describes this development of crash type methodology:

The crash typologies developed by Cross and Fisher, by NHTSA, and in the FHWA study evolved into the development of an automated crash typing software, the Pedestrian and Bicycle Crash Analysis Tool (PBCAT) (Harkey et al., 1999), which is currently being further refined for version 2.

Crash Type 11 is

Motorist overtaking bicyclist Description—The motorist was overtaking the bicyclist at the time of the crash.

One of the accompanying figures shows a motorist at night coming upon a lighted cyclist riding on the right edge of a narrow lane in a sharp right hand curve. The implication is that the motorist is about to strike the bicyclist from the rear. In the countermeasures for such an accident scenario, nothing is said of the bicyclist controlling the lane or of the motorist violating the basic speed law by driving too fast for conditions.

The other figure shows a car starting to pass a curb hugging cyclist on a narrow two lane road with a car coming the other way. Again, the report does not propose controlling the lane as a countermeasure. And the report says nothing about motorists thinking that is OK to pass bicyclists anywhere, any time, under any circumstances.

Because the report contains no analysis of the risk of a cyclist controlling a narrow lane being hit from behind, I consider it flawed. It repeats the mistaken analysis that because bicyclists who are hit from behind are at greater risk of serious injury or death, all bicyclists riding in narrow lanes are at greater risk. And because it doesn't analyze overtaking accidents in more detail, it does not address the possible countermeasure of controlling a narrow lane. More seriously, it does not address the countermeasure of integrating bicyclists with traffic.

Instead, the report focuses on countermeasures such as bike lanes and bike boxes that segregate bicyclists from traffic. Until we can gain some influence in the preparation of research reports like this, we will have a limited influence on unsafe practices like the installation of bike boxes in Portland and NYC.

Bob Shanteau

Robert M Shanteau, PhD, PE
Consulting Traffic Engineer
13 Primrose Cir
Seaside, CA 93955-4133
Voice: (831) 394-9420
Cell: (831) 917-0248
FAX: (831) 394-6045

Sunday, April 6, 2008

Report on April 2 AB 1581 Subcommittee meeting

The AB 1581 Subcommittee held its second meeting on April 2. Recall that AB 1581 requires that new and modified traffic actuated signals in California be able to detect bicycles and motorcycles, but only after Caltrans adopts guidelines for detection and signal timing. The AB 1581 Subcommittee will be presenting its recommendations to the

California Traffic Control Devices Committee to consider at its next meeting on May 29, 2008, in the CSAA building in San Francisco. The CTCDC in turn will recommend changes in the California Manual on Uniform Traffic Control Devices, which is administered by Caltrans. So actual changes are still many months and many meetings away. But the AB 1581 Subcommittee pretty much finished its work at the April 2 meeting.

Attending the meeting in person were Ahmad Rastegarpour, Kai Leung, Richard Haggstrom, and David Priebe from Caltrans, James Lombardo from ABATE (motorcycle advocacy), Damon Curtis from San
Francisco, and me. David Roseman from Long Beach and Sean Skehan from the City of Los Angeles attended by telephone.

The meeting was very productive and we agreed on the following recommendations:
  1. Bicycle/motorcycle detection will be performance-based. At least 95% of bicycles and motorcycles that stop within the detection zone (defined below) shall be detected.

  2. The default detection zone shall be a 6'x6' box at the the stop line centered within the lane, except that if the lane is more than 12' wide, the edge of the box shall be 3' from the lane line. If the detection system is capable of detecting bicycles and motorcycles anywhere within the default detection zone, then no marking is necessary.

  3. A detection system that is capable of detecting the reference bicycle/motorcycle plus rider in a detection zone at least 3' wide but less than 6' wide shall be allowed, but only if a Bicycle Detector Symbol is placed at the center of the narrower detection zone.

  4. The reference bicycle/motorcycle and rider shall consist of a folding bicycle with non-ferromagnetic frame and 16" wheels with aluminum rims and stainless steel spokes, such as the Dahon Curve SL, plus a person 4' tall weighing 90 pounds standing over the bicycle.

  5. To be allowed for use at actuated traffic signals in California, a detection system will need to be certified by its manufacturer to meet the performance requirements of detecting the reference bicycle/motorcycle and rider stopped in either the default detection zone or the narrower detection zone at least 95% of the time under actual operating conditions.

  6. For the purposes of setting up the detection at a new or modified signal, a signal technician may choose to use an equivalent rim/rider consisting of a 20" BMX aluminum rim mounted in a wooden frame and set vertically 1.5" above the pavement plus a plywood cutout representing a person 4' tall weighing 90 pounds standing over the rim.

  7. Caltrans will approach manufacturers of carbon fiber rims to request that they either include a shorted coil of wire in the rim during the manufacturing process or else attach a sticker notifying the user that the rim will not trip inductive loops at traffic actuated signals.

  8. The minimum green time at traffic actuated signals shall be long enough such that, when combined with the yellow and all-red times, most bicyclists starting from a stop at the beginning of green will have enough time to substantially clear the intersection.

  9. The Subcommittee decided not to address the all-red time as a separate issue. Their reasoning was that CVC Section 21451 already requires that drivers facing a green signal "shall yield the right-of-way to other traffic and to pedestrians lawfully within the intersection or an adjacent crosswalk." Thus bicyclists who enter an intersection toward the end of yellow (which is legal in California) may not have enough time to substantially clear the intersection before conflicting traffic receives a green signal.
I presented these recommendations to the California Bicycle Advisory Committee the following day. CBAC made some helpful suggestions, one of which resulted in a refinement of the reference bicycle/motorcycle definition. CBAC also decided to address the issue of the many traffic actuated signals that are not addressed by AB 1581 by recommending to the CTCDC that the CA MUTCD provide for a 10 year compliance period for all signals in California to meet the recommended bicycle/motorcycle detection guidelines.

Report on March 4 AB 1581 Subcommittee meeting

At its January meeting, the California Traffic Control Devices Committee (CTCDC) created the AB 1581 Subcommittee to develop recommendations for the CTCDC to consider at its next meeting on May 29, 2008, at the CSAA building in San Francisco. The AB 1581 Subcommittee held its first meeting on March 4 after two cancellations and a reversal of the second cancellation.

The on-again off-again scheduling, along with some incorrect email addresses, hurt the attendance. Attending the meeting in person were Ahmad Rastegarpour, Kai Leung, and Heather Loebs from Caltrans, James Lombardo from ABATE (the motorcycle advocacy group that sponsored the bill), Damon Curtis from San Francisco, and me. The invitation to David Roseman from Long Beach went to the wrong email address but fortunately he was reached by telephone. Neither Ken McGuire, the Caltrans Bicycle Coordinator at headquarters nor his assistant David Priebe attended, which I later learned was because neither one received word that the March 4 meeting was back on again. An invitation went to Sean Skehan from the City of Los Angeles but I later learned that it was sent to an outdated email address. Unfortunately, Mr. Skehan could not be reached by telephone that day.

Here is the agenda that was emailed with the invitations:
  • Introductions
  • Identify Deliverables
  • Document Content (Standards, Specifications, and Guidelines)
  • Type of Document
  • Level of Detail
  • Current Detection Standards (Type "D" Inductive Loop, VDS)
  • Other Standards
  • Adopt/Develop Detection Standards, Specifications, and Guidelines
  • Schedule
Ahmad Rastegarpour chaired the meeting. He identified the deliverable as a recommendation to the CTCDC for changes to the California Manual on Uniform Traffic Control Devices (CA MUTCD) to address the changes required by the passage of AB 1581, specifically with regard to detection of motorcycles and bicycles as well as signal timing for bicycles at new and modified
traffic actuated signals. Existing traffic actuated traffic signals for which the detection is not being modified are not within the subcommittee's scope.

Damon Curtis discussed the problems that the City and County of San Francisco has with inductive loops including: (1) bicyclists and motorcyclists not knowing where to stop within a loop in order to be detected, and (2) loops being short-lived because of utility cuts and pavement failures. Video detection is limited by fog and a lack of clarity in coastal areas. Therefore SF is experimenting with Sensys Networks wireless detectors. These are fist-sized battery powered magnetic detectors that are placed in a 6" hole cut in the pavement and covered with sealant. The internal battery lasts about 10 years after which another hole is cut and a new detector installed. When a vehicle passes over the detector, the detector sends a radio signal to a roadside sensor that then forwards the detection to the signal controller.

Mr. Curtis reported on some tests that SF had conducted on the Sensys detectors with bicycles. He later sent out a report and a spreadsheet on the test. He found that at a sensitivity setting that just rejected vehicles in the adjacent lane, a conventional bicycle with metal wheels as well as a Dahon folding bicycle could be detected 18" away and a simulated carbon fiber bicycle 6" away.

Kai Leung reported that he also had performed a test on the Sensys detectors, but at the default sensitivity setting, which was quite a bit lower than the setting that Damon Curtis had used. Mr. Leung found that a conventional bicycle could be detected 6" away but a "fancy" bicycle [which turned out to be a Trek 5200 with a full carbon frame and fork and aluminum rims] owned by a co-worker could not be detected until a ceramic magnet was placed in its water bottle holder.

David Roseman encouraged the subcommittee to recommend performance-based standards rather than be specific to a particular technology. He said that when loops work, they are 99.9% accurate but that video detection is not that good. He did not want to preclude adoption of other detection technology besides inductive loops. Ahmad Rastegarpour said that the technology could be handled in Caltrans Standard Plans and Specifications rather than in the CA MUTCD.

Mr. Roseman discussed the need for detection of bicycles and motorcycles to be added to the preventive maintenance checklist performed by signal technicians. Various levels of preventive maintenance are performed at different intervals, and it was generally agreed that detection of bicycles and motorcycles should be checked at least once a year.

I brought up the need to adjust the sensitivity of detectors to pick up bicycles and motorcycles when an actuated traffic signal is first turned on. I noted that currently the usual procedure is to start at the lowest sensitivity and increase it until cars are detected reliably. That results in poor bicycle and motorcycle detection. I recommended that instead the procedure should start at the highest sensitivity and decrease it until vehicles in the adjacent lane are no longer detected. Then a check should be made to insure that a typical bicycle is detected. David Roseman said that Long Beach sets the sensitivity the way I described and was pleased with the results.

The subcommittee then discussed the need to define a "reference vehicle" for the purposes of detecting bicycles and motorcycles. I volunteered to investigate this issue and report back at the next meeting. Among other things, I will check with Sensys Networks to find out just how their detectors work and what materials their detector can pick up.

I then gave the presentation that I had planned to give at the January CTCDC meeting but could not because it was not a public input item. I stated that bicyclists are having trouble being detected now and are not in favor of waiting for decisions on signal timing before implementing changes in the CA MUTCD to improve bicycle detection. James Lombardo, lobbyist for the motorcycle advocacy group ABATE agreed.

I went over how inductive loops detect vehicles like bicycles and motorcycles, which appear to a loop as a vertical conducting plate, as opposed to cars and trucks, which appear as a horizontal conducting plate. And because a bicycle's or motorcycle's wheels are closer to the ground than the frame, the inductive loop detects the metal rims rather than the frame or other components. Probably the hardest vertical vehicle to detect with a loop is a bicycle or motorcycle with small wheels, since the effect of the induced electrical currents would be smaller than with a larger wheel. A folding bicycle or small motorcycle should therefore be the reference vertical vehicle. I agreed to do some testing not only with loops but also with video detection and other detection technologies to see if that is true. Reno A&E, a manufacturer of loop detectors, provided test equipment and 3 detectors to me a few years ago that I have used to conduct testing of bicycle detection in the past and can use again to conduct this testing.

I covered how bicycles and motorcycles are detected best over a conventional Type A (6' square) loop when they stop on top of a sawcut and cannot be detected when they stop in the center of the loop. For a conventional loop that is not visible, a marking such as a Bicycle Detector Symbol is needed to show the bicyclist or motorcyclist where to stop in order to be detected. David Roseman said that he had not received any complaints from motorcyclists despite the lack of markings, and I suggested that may be because motorcyclists are trained to ride in either the right or left wheelpath and therefore just happen to stop on top of the sawcut of a Type A loop. James Lombardo says that he hears numerous complaints from motorcyclists in the Palm Springs area that they are not detected. I asked him to request motorcyclists there to send me photos of locations where they are having trouble so I can perhaps diagnose the problem.

Currently the only loop configuration in the Caltrans Standard Plans that will pick up a bicycle or motorcycle with metal rims across its width is a Type D loop. This is a diagonal quadrupole created with straight sawcuts. I presented several other designs for diagonal quadrupole loops, including the quadracircle, which is a circular loop with one or two diagonal sawcuts with the wire placed in a figure-8. I noted that the detection zone of a diagonal quadrupole loop falls off very quickly outside the loop, so that it can be made larger than a conventional square or round loop and still reject vehicles in the adjacent lane.

A non-metal wheel, such as one made of carbon fiber or plastic, cannot be detected by an inductive loop. Such a wheel can be made to be detected, however, by wrapping several turns of fine wire around the rim and splicing the ends together. I indicated that bicycle and motorcycle advocates will need to educate manufacturers, repair shops and riders of this fact.

The last major issue in my presentation was the location of the detection zone. Currently, the Caltrans Standard Plans show no inductive loops wider than 6', so bicyclists and motorcyclists who stop outside such loops are not detected. But diagonal quadrupole loops can be constructed larger than 6' and still reject vehicles in the adjacent lane, thus creating a larger detection zone for a bicycle or motorcycle to stop in.

I ended my presentation with the following recommendations: (1) Immediately require Bicycle Detector Symbols at all traffic actuated signals, (2) Eventually retrofit all traffic actuated signals either with diagonal quadrupole as the head loop, appropriately located and sized, or out-of-pavement bicycle detection, (3) Educate bicyclists and bicycle manufacturers of need to use several turns of wire on non-metal bicycle wheels, (4) Include diagonal quadrupole loops in future research, (5) Include additional diagonal quadrupole loops (e.g., quadracircle) on Caltrans standard plans, and (6) Continue research into inductive loops, out-of-pavement detection and extended green intervals for bicyclists.

David Roseman in particular was interested in the quadracircle loops that I showed. He asked me if there were any operating examples of quadracircle loops with two diagonal sawcuts, and I told him that I had seen one in Monterey that had been cut by a contractor. When I saw it, I recognized that it was an improved version of the Caltrans Type D loop.

We agreed that for all new and modified signals, the "default detection zone" would be a 6' square centered in the lane at the limit line, in which case no special marking would be required. For a bike lane, the default detection zone would be 5' wide. If the actual detection zone were smaller than this in either a regular lane or a bike lane, a Bicycle Detector Symbol would be required, in which case the detection zone would be at least 3' wide, centered on the Bicycle Detector Symbol.

The subcommittee was concerned about how close the Bicycle Detector Symbol should be placed adjacent to a high speed lane out of fear that a waiting cyclist might be struck by a passing car or truck. It was decided that the Bicycle Detector Symbol would be placed no closer than 2.5' from the middle of the lane stripe. Furthermore, the preferred position for the Bicycle Detector Symbol in a through or left turn lane would be 1.5' to the right of the center of the lane.

Ahmad Rastegarpour reported that Caltrans was working on a Traffic Operations Directive to be sent to the Districts that would direct them to install Type D loops or video detection in all lanes at all new or modified traffic signals and to install Bicycle Detector Symbols in the rightmost left turn lane and, if there was no bike lane, in the rightmost through lane, or if there is a bike lane, in the bike lane itself.

Ahmad Rastegarpour reported that PATH had been unsuccessful in its attempts to distinguish between bicycles and other vehicles for the purposes of signal actuation and that Caltrans was redirecting PATH to the problem of signal timing for bicyclists. PATH is settling on a startup time of 2.5 sec and an average speed of 12 mph to cover the majority of bicyclists, as they reported to the CTCDC in January. They are concentrating on the length of the initial green interval rather than on the length of the all-red, however.

At the end of the meeting, Kai Leung asked whether bicyclists and motorcyclists would be willing to place radio frequency (RF) tags on their machines for the purposes of traffic signal actuation. This would fit in with a new effort among transportation professionals to automate the transportation system using Vehicle Infrastructure Integration (VII). Traffic signals would be equipped with transponders that detect any RF tags in the area. This would eliminate the need for inductive loops to detect motorcycles and bicycles. If other motor vehicles had RF tags as well, it would eliminate the need for loops altogether, which is an important objective for Caltrans. Obviously, this change would not happen overnight, but Caltrans is looking 10 or 20 years down the road to make sure that motorcycles and bicycles are not left out of the next detection technology like they were with inductive loops from the 1960's to now. I agreed to coordinate the effort to collect the feedback and report back to the subcommittee and its April 2 meeting.

Sunday, February 10, 2008

Barrier posts (bollards) on bike paths in California are overused

The California MUTCD reads:

Section 9C.101(CA) Barrier Posts on Class I Bikeways

Before a decision is made to install barrier posts, consideration
needs to be given to the implementation of other remedial measures, such
as Bike Path Exclusion (R44A(CA)) signs (see Section 9B.07) and/or
redesigning the path entry so that motorists do not confuse it with
vehicle access.

It could be necessary to install barrier posts at entrances to bike
paths to prevent motor vehicles from entering. When locating such
installations, care needs to be taken to assure that barriers are well
marked and visible to bicyclists, day or night (i.e., install reflectors
or reflectorized tape).


An envelope around the barriers should be striped as shown in Figure
9C-2. If sight distance is limited, special advance warning signs or
painted pavement warnings should be provided. Where more than one post
is necessary, 1.5 m (5 ft) spacing should be used to permit passage of
bicycle-towed trailers, adult tricycles, and to assure adequate room for
safe bicycle passage without dismounting. Barrier post installations
should be designed so they are removable to permit entrance by emergency
and service vehicles.

Generally, barrier configurations that preclude entry by motorcycles
present safety and convenience problems for bicyclists.

Such devices should be used only where extreme problems are encountered.

Note that Figure 9C-2 shows no barriers are shown in the path itself.

Chapter 1000 of the Highway Design Manual is still current (it has not
been superseded by the California MUTCD). It states:

Topic 1003 - Design Criteria

1003.1 Class I Bikeways

(15) Barrier Posts. It may be necessary to install barrier posts at
entrances to bike paths to prevent motor vehicles from entering. For
barrier post placement, visibility marking, and pavement markings, see
the MUTCD and California Supplement, Section 9C.101.
Generally, barrier configurations that preclude entry by motorcycles
present safety and convenience problems for bicyclists. Such devices
should be used only where extreme problems are encountered.

It would appear that based on the guidance in both the California MUTCD
and the HDM, barrier posts (bollards) are overused on bike paths in California.

Saturday, February 9, 2008

Two bicycle items (plus one) at January 31, 2008, CTCDC meeting

Three items were on the agenda California Traffic Control Devices Committee (CTCDC) that were of interest to bicycling advocates:

1. The Committee considered a proposal to amend the policy of the Speed Limit Sign contained in the California Manual on Uniform Traffic Control Devices (MUTCD). This applies to bicycling because one of the tools for improving traffic conditions for bicyclists is to control the traffic speeds. Here is the agenda item.

The proposal would clarify the procedures for Engineering and Traffic Studies (E&TS) to set the speed limit within 5 mph of the 85th percentile speed of free flowing traffic, providing that the speed limit could be set 5 mph lower if indicated by unusual conditions not readily apparent to drivers, but in any case not below the 50th percentile speed.

Several cities raised objections to the proposal based on the fact that speed distributions are typically so narrow that the first 5 mph increment above the 50th percentile speed may also be above the 85th percentile speed. Since previously the speed limit was set at the first 5 mph increment below the 85th percentile speed, they would be required to raise the speed limit on a substantial percentage of their streets.

The Committee asked about the leeway that police give in enforcing speed limits. I told them about a meeting I had with the Traffic Commissioner when I first started as Traffic Engineer for the City of Monterey in 1990 to go over our E&TS procedures. He said our procedures were fine, but then I asked him about the latitude he gave for speeding citations in his court. He said he gave 12 mph over the speed limit. I asked why such a large number, and he said that traffic citations are handled as criminal matters and the burden of proof was beyond a reasonable doubt. He said that there was considerable doubt about the accuracy of radar, and this doubt required a large latitude.

The Committee members were taken aback that the latitude allowed by traffic court judges was this large, but other traffic engineers in attendance corroborated my story. The co-chair asked if the 12 mph latitude applied to freeways with speed limits of 65 mph, and I had to admit that I did not know, because Monterey's highest speed limit was 35 mph.

I then said that we could think of speed enforcement as a team consisting of traffic engineers, police, and judges, but that although engineers were setting speed limits honestly and police were doing the best they could to enforce them, the judicial system was dropping the ball. I said that if the traffic court judges used a smaller latitude, then we would not be having this argument. I said that the judges were basing their decisions on some anti-radar propaganda, including the myth of a radar gun measuring a tree moving at 40 mph, and said that we need to educate the judges on the accuracy of radar.

During the next break, George McDougall, Statewide Radar Coordinator for the CHP introduced himself to me. He told me about the newest radar guns that take two readings, one of the vehicle and one of the ground, and then calculate the difference. This allows for enforcement from moving vehicles. It is also extremely accurate, certainly to within 3 mph.

The CTCDC approved the new wording, including the 50th percentile floor. This next goes to Caltrans which will make the decision of whether to include the wording in future editions of the CA MUTCD.

2. San Francisco applied for permission to install signs to warn bicyclists that motorists may be making illegal right turns. Here is the agenda item.

Jack Fleck, SF's Traffic Engineer, and Damon Curtis, Associate Engineer Bicycle Program, attended the meeting. Here is Mr. Fleck's presentation.

Mr. Fleck described the problem as bicyclists who pick up speed on this downhill part of Market are being right-hooked (my term, not his) by drivers making illegal right turns. His presentation contained pictures of no right turn signs, delineators (flexible cylindrical posts) and a concrete median to try to prevent motorists from turning right at Octavia. Despite all this, he said that some automobile drivers are slowing to a crawl and making the turn anyway in front of bicyclists who are traveling fast on this downhill and passing cars on the right that they do not think will be making an illegal right turn at Octavia.

He proposed two alternates for signs, one with wording that says: BICYCLISTS WATCH FOR PROHIBITED RIGHT TURNS, and the other that says: BICYCLISTS WATCH FOR CARS MAKING PROHIBITED RIGHT TURNS.

I had questions about the wisdom of having a bike lane at that location, particularly because bicyclists could not leave the bike lane to pass slow motor vehicles on the left because of the delineators and median. I recommended a wide outside lane instead to allow bicyclists to integrate with motor vehicles. Jack Fleck responded that the SFBC considered that idea but rejected it out of concern for cyclists who were not comfortable "mixing it up with traffic."

The CTCDC approved SF's request for experimentation, with the proviso that the experiment include several alternative schemes, including red light cameras to catch illegal right turns (which would be allowed by AB 23).

After I got home, I thought of a different legend for a sign from the one proposed: BICYCLISTS - NO PASSING ON RIGHT IN INTERSECTION, perhaps with a picture of a car making a right turn in front of a bicyclist, such as this sign on the Stanford University campus:

I think that the message BICYCLISTS - NO PASSING ON RIGHT IN INTERSECTION plus the picture above get the message across to the bicyclist exactly what the hazard is and what to do about it. If a car in the right travel lane is slowing down approaching Octavia, then anticipate that it is about to make a right turn and STOP!!!!

I have suggested to SF and SVBC that a sign with the wording and picture above be included in the experiment.

3. Caltrans presented its plans to address AB 1581 concerning detection of bicycles and motorcycles at traffic actuated signals. Here is the agenda item.

The CTCDC chair said that this was a discussion item only and that public input would occur at their next meeting on April 24.

Ahmad Rastegarpour from Caltrans' Electrical Systems Branch gave this presentation on Caltrans' plans.

Mr. Rastegarpour stressed the Caltrans emphasis on distinguishing bicycles from motor vehicles for the purpose of providing additional minimum green time.

Then Dr. Steven Shladover from UC Berkeley gave this presentation on bicycle crossing times.

Dr. Shladover's email transmitting his presentation contained the following proviso: "I would caution that these presentation slides were not intended to be a stand-alone document for general distribution and are not entirely self-explanatory, but were meant to be shown with a narration that fills in additional information not shown here."

Members of the CTCDC expressed alarm over the implications of Dr. Shladover's findings on traffic signal operations, particularly on the potentially large (8 sec was mentioned) all-red times.

I was not allowed to give the presentation that I had prepared, although printed copies that I prepared were distributed to the Committee.

Instead, I said that neither the bicyclist nor motorcyclist communities had been given an opportunity to provide input on Caltrans' plans. I said that I had given a presentation in October to the Electrical Systems Branch, but that Mr. Rastegarpour was not there that day, and that I had given a copy of the presentation to Caltrans during the November Bicycle Advocacy Summit with the Director. I pointed out that a member of the motorcycle community was also at the meeting (I had notified ABATE and AMA, and Chuck Pederson from ABATE was there). I said that there were errors in Caltrans' presentation, including their assertion that motorcycles were detected by existing loops.

The CTCDC chair then directed that a subcommittee be formed to work on the plan. Mr. Rastegarpour will chair the committee, and members will include representatives from the Cities of Los Angeles, Long Beach, (San Francisco?), along with representatives from the bicycling community (me) and the motorcycling community (to be selected).

Afterwards, Chuck and I spoke with Mr. Rastegarpour outside the meeting room. Mr. Rastegarpour asked me to call Ken McGuire and tell him about the formation of the subcommittee, which I did. I told Mr. Rastegarpour that I would be in Sacramento next Thursday for the CBAC meeting and Friday afternoon for the Bicycle Advocacy Summit, and requested a meeting with him on Friday morning.

Monday, January 21, 2008

FAQ Rec.Bicycles Frequently Asked Questions Posting Part 4/5 Traffic Detector Loops

A traffic loop detects metal objects such as cars and bicycles based on the change in inductance that they induce in the loop. The loop is an inductor in an LC circuit that is tuned to resonate at a certain frequency. A metal plate over the loop (like a car) causes the magnetic flux to be shorted, reducing the inductance of the loop. This causes a change in resonant frequency, which is detected and sent to the signal controller. One of the ways of testing a loop is to create a loop about 2 feet in diameter with several turns of wire (connecting the ends) and placing the test wire in the middle of the traffic loop. The test wire should cause a detection, if all is working.

The same effect is seen with a vertical piece of metal, such as a bicycle, but is weaker. Because aluminum conducts electricity quite well, aluminum rims help. Steel rims are OK. Non-metal rims cannot be picked up at all. A bicycle with aluminum rims will cause about 1/100 the change in inductance of a car.

It is always possible to set a detector's sensitivity to pick up a bicycle. The trade-off is in longer detection times and the possibility of false detections from vehicles in adjacent lanes. Most people who set signal detectors use the lowest sensitivity setting that will pick up cars reliably.

I advocate using the highest setting that will avoid picking up vehicles in adjacent lanes. Digital circuits used in modern detectors can use high sensitivity settings without unacceptable increases in detection times. Unfortunately, there are still a lot of old detectors out there, and most people who work on signals use principles based on the performance characteristics of old detectors.

In any case, bicyclists should, as a general rule, place their wheels over one of the slots to maximize their chance of being detected. That is where the magnetic field perpendicular to the wheels is strongest. Bouncing the bike or moving it back and forth does no good. If you have a metal frame, another tactic that may work is to lay the bicycle down horizontally inside the loop until the light turns green.

Advancements are under way that may make traffic loops obsolete some day. In particular, radar, infrared and sound detectors have been introduced. Systems based on video cameras are especially promising. Such systems can easily detect bicycles. Such a system may even be able to detect pedestrians some day.