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Sean Skehan from the City of Los Angeles but I later learned that it was sent to an outdated email address.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.
